Waste gas purification device

Abstract

This invention provides an exhaust gas purification device that can adequately maintain the honeycomb filter in a range-extended electric vehicle by retaining it under surface pressure without damage. The exhaust gas purification device comprises a honeycomb filter, a gasket wound around the outer periphery of the honeycomb filter, and a metal can housing the honeycomb filter and gasket internally. The honeycomb substrate has a porous partition wall dividing into multiple cells extending from the inflow side end face to the outflow side end face. The cells of the honeycomb substrate include: a first cell open on the inflow side end face and sealed on the outflow side end face, and a second cell open on the outflow side end face and sealed on the inflow side end face. The average coefficient of thermal expansion in the radial direction orthogonal to the direction of cell extension, from 40°C to 800°C, is 1.4 ppm / K or higher.

Description

Technical Field

[0001] This utility model relates to an exhaust gas purification device for range-extended electric vehicles, which have an engine that serves as a range extender for charging a battery. Background Technology

[0002] For gasoline engine exhaust, purification of CO, HC, NOx components and removal of particulate matter are required. Patent Document 1 discloses an exhaust gas purification device that connects a honeycomb structure (honeycomb catalyst body) and a honeycomb filter (sealed honeycomb structure) in series; however, this exhaust gas purification device is not specifically designed for range-extended electric vehicles. Gaskets (buffer materials) are wound around the outer periphery of both the honeycomb structure and the honeycomb filter, and these honeycomb structures, honeycomb filters, and gaskets are housed inside a metal canister.

[0003] Patent Document 2 discloses a correlation between the average coefficient of thermal expansion in the axial direction of a cellular filter and the thermal shock limit of the cellular filter (particulate filter). Patent Document 2 explains that the thermal shock limit can be improved by suppressing the average coefficient of thermal expansion to a lower level.

[0004] Existing technical documents

[0005] Patent documents

[0006] Patent Document 1: Japanese Patent Application Publication No. 2011-167581

[0007] Patent Document 2: Japanese Patent Publication No. 2012-509765 Utility Model Content

[0008] The problem to be solved by the utility model

[0009] In recent years, as a countermeasure against global warming, there has been a strong demand to reduce CO2, and range-extended electric vehicles (REEVs) with gasoline engines designed to extend battery capacity are being put into practical use. Exhaust gas purification is also required in such REEVs, and the exhaust gas purification device disclosed in Patent Document 1 is being considered for integration into REEVs.

[0010] In range-extended electric vehicles (REEVs), the engine switches between operation and shutdown more frequently compared to conventional vehicles that use a gasoline engine as their power source. Furthermore, when a gasoline engine is running, there is a tendency for the exhaust gas temperature to be higher even under optimal efficiency conditions. Therefore, in REEVs, the canister housing the honeycomb filter and other components undergoes frequent thermal expansion and contraction, causing fluctuations in the surface pressure exerted on the honeycomb filter from the canister. Since the honeycomb filter is heavier than the honeycomb structure, it is prone to shifting within the canister when the surface pressure decreases. Although the decrease in surface pressure due to the canister's thermal expansion has been considered, and a higher surface pressure is set for the honeycomb filter during canister contraction, the honeycomb filter may still be damaged due to the increased surface pressure.

[0011] This invention was made to solve the aforementioned problems, and one of its objectives is to provide an exhaust gas purification device that can adequately maintain the honeycomb filter in a range-extended electric vehicle by maintaining it under surface pressure without damaging the honeycomb filter.

[0012] Methods for solving problems

[0013] [1] In one embodiment, this utility model relates to an exhaust gas purification device for a range-extended electric vehicle, wherein the range-extended electric vehicle has a gasoline engine as a range extender for charging a battery; the exhaust gas purification device comprises:

[0014] A honeycomb filter includes a honeycomb substrate and a sealing portion. The honeycomb substrate has a porous partition wall that divides into multiple pores extending from an inflow side end face to an outflow side end face. The sealing portion seals the pores on the inflow side end face or the outflow side end face. The pores of the honeycomb substrate include a first pore that opens on the inflow side end face and is sealed on the outflow side end face, and a second pore that opens on the outflow side end face and is sealed on the inflow side end face. A gasket is wound around the outer periphery of the honeycomb filter. A metal can housing the honeycomb filter and the gasket inside. The average coefficient of thermal expansion in the radial direction orthogonal to the direction in which the pores extend is 1.4 ppm / K or higher, ranging from 40°C to 800°C.

[0015] [2] This utility model may relate to the exhaust gas purification device described in the first item, wherein the average thermal expansion coefficient in the radial direction orthogonal to the direction of the above-mentioned grid extension at 40°C to 800°C is less than 2.1ppm / K.

[0016] [3] This utility model may relate to the waste gas purification device described in the first item, wherein the opening ratio of the honeycomb substrate is 77% or more, the porosity of the partition wall of the honeycomb filter in the state without catalyst is 60% or more, or the porosity of the partition wall of the honeycomb filter in the state with catalyst is 40% or more.

[0017] [4] This utility model can relate to the waste gas purification device described in any one of the first to third items, wherein the pore density of the honeycomb filter is 54 pores / cm². 2 above.

[0018] [5] This utility model may relate to the exhaust gas purification device described in any one of the first to third items, wherein the partition wall of the honeycomb filter contains more than 0.5 wt% cerium.

[0019] [6] This utility model may relate to the exhaust gas purification device described in any one of the first to third items, wherein the average coefficient of thermal expansion in the radial direction orthogonal to the direction of extension of the above-mentioned pores at 40°C to 800°C is 1.6ppm / K or higher.

[0020] [7] The present invention may relate to an exhaust gas purification device as described in any one of the first to third items, wherein the exhaust gas purification device further comprises a honeycomb structure disposed upstream of the honeycomb filter, the honeycomb structure having a second honeycomb substrate having a porous partition wall dividing a plurality of pores extending from a second inflow side end face to a second outflow side end face, the two ends of the pores of the second honeycomb substrate being open.

[0021] Utility Model Effect

[0022] According to one embodiment of the exhaust gas purification device of this utility model, the average coefficient of thermal expansion in the radial direction orthogonal to the direction of the pore extension at 40°C to 800°C is 1.4ppm / K or higher. Therefore, the honeycomb filter can be adequately maintained by maintaining it under surface pressure in a range-extended electric vehicle without damaging the honeycomb filter. Attached Figure Description

[0023] Figure 1 This is an explanatory diagram showing a range-extended electric vehicle equipped with an exhaust gas purification device according to an embodiment of the present invention.

[0024] Figure 2 yes Figure 1 A cross-sectional view of the waste gas purification device.

[0025] Figure 3 It means Figure 2 Front view of the inflow side end face of the cellular filter.

[0026] Figure 4 It means Figure 2 A 3D view of a honeycomb filter.

[0027] Figure 5 It means Figure 2 The front view of the second inflow side end face of the honeycomb structure.

[0028] Figure 6 It means Figure 2 A three-dimensional diagram of a honeycomb structure.

[0029] Figure 7 This is a graph showing the relationship between the cerium content in the partition walls of the cellular filters in the embodiments and comparative examples and the average coefficient of thermal expansion in the radial direction.

[0030] Explanation of reference numerals in the attached figures

[0031] 1: Range-extended electric vehicle; 3: Battery; 4: Gasoline engine; 4b: Exhaust gas; 5: Exhaust gas purification device; 6: Honeycomb filter; 60: Honeycomb substrate; 61: Inflow side end face; 62: Outflow side end face; 63: Cell; 631: First cell; 632: Second cell; 64: Partition wall; 65: Sealing part; 7: Gasket; 8: Tank body; 9: Honeycomb structure; 90: Second honeycomb substrate; 91: Second inflow side end face; 92: Second outflow side end face; 93: Cell; 94: Partition wall. Detailed Implementation

[0032] Hereinafter, embodiments for implementing the present invention will be described with reference to the accompanying drawings. The present invention is not limited to any particular embodiment, and can be embodied by modifying the constituent elements without departing from its spirit. Furthermore, various embodiments can be formed by appropriately combining the multiple constituent elements disclosed in each embodiment. For example, some constituent elements may be deleted from all the constituent elements shown in the embodiments. Furthermore, constituent elements from different embodiments may be appropriately combined.

[0033] <About Range Extended Electric Vehicles>

[0034] Figure 1 This is an explanatory diagram showing a range-extended electric vehicle 1 equipped with the exhaust gas purification device 5 according to an embodiment of this utility model. (See diagram below.) Figure 1 As shown, the range-extended electric vehicle 1 has a motor 2, a battery 3, a gasoline engine 4, and an exhaust gas purification device 5.

[0035] Motor 2 is the power source for driving. That is, the output shaft of motor 2 is connected to wheel 1a, and the output of motor 2 can drive wheel 1a to move the range-extended electric vehicle 1. Battery 3 is connected to motor 2. Motor 2 can operate using the electricity stored in battery 3. Motor 2 can be configured to perform regenerative operation, or the electricity generated by motor 2 can be stored in battery 3.

[0036] The gasoline engine 4 is an internal combustion engine that uses gasoline as fuel and serves as a range extender for charging the battery 3. The output shaft of the gasoline engine 4 is connected to a generator, allowing the generator to be driven by the output of the gasoline engine 4. In the range-extended electric vehicle 1, when the charging rate of the battery 3 decreases, the gasoline engine 4 generates electricity, thereby extending the driving range based on the motor 2 and the battery 3. The generator can be the motor 2 or a separate unit. The gasoline engine 4 can be used solely as a power source for generating electricity, and not as a power source for driving.

[0037] Range-extended electric vehicles 1 are sometimes also referred to as hybrid vehicles. Hybrid vehicles also include, for example, plug-in hybrid vehicles that can connect an external power source, such as a commercial electric system, to the battery 3.

[0038] An exhaust gas purification device 5 is installed in the exhaust system 4a of the gasoline engine 4 to purify the exhaust gas 4b from the gasoline engine 4. The purification of exhaust gas 4b includes the purification of gaseous components such as NOx, HC, and CO based on a catalyst, as well as the removal of particulate matter generated by the combustion of lubricating oil and fuel. The particulate matter includes ash generated by lubricating oil and fuel.

[0039] <About exhaust gas purification devices>

[0040] then, Figure 2 yes Figure 1 A cross-sectional view of the exhaust gas purification device 5. Figure 3 It means Figure 2 Front view of the inflow side end face 61 of the honeycomb filter 6. Figure 4 It means Figure 2 A 3D view of the honeycomb filter 6. Figure 5 It means Figure 2 The front view of the second inflow side end face 91 of the honeycomb structure 9. Figure 6 It means Figure 2 A three-dimensional view of the honeycomb structure 9.

[0041] like Figure 2 As shown, the exhaust gas purification device 5 has a honeycomb filter 6, a gasket 7, and a tank 8.

[0042] The honeycomb filter 6 has a honeycomb substrate 60 and a sealing portion 65. The honeycomb substrate 60 has a porous partition wall 64 dividing a plurality of cells 63 extending from an inflow-side end face 61 to an outflow-side end face 62. The sealing portion 65 seals the cells 63 at either the inflow-side end face 61 or the outflow-side end face 62. The cells 63 of the honeycomb substrate 60 include a first cell 631 that opens at the inflow-side end face 61 and is sealed at the outflow-side end face 62, and a second cell 632 that opens at the outflow-side end face 62 and is sealed at the inflow-side end face 61. The honeycomb filter 6 is a wall-flow type. That is, exhaust gas 4b from the inflow-side end face 61 enters the first cell 631, passes through the partition wall 64 between the first cell 631 and the second cell 632, enters the second cell 632, and is discharged from the outflow-side end face 62. As exhaust gas 4b passes through partition wall 64, the particulate matter contained in exhaust gas 4b is captured within the honeycomb filter 6. That is, as a purification of exhaust gas 4b, the honeycomb filter 6 at least removes particulate matter. The honeycomb filter 6 is disposed downstream of the honeycomb structure 9 in the exhaust system 4a of the range-extended electric vehicle 1 relative to the flow of exhaust gas 4b.

[0043] The gasket 7 is wound around the outer periphery of the honeycomb filter 6. The tank 8 is a metal component that houses the honeycomb filter 6 and the gasket 7 inside. The honeycomb filter 6 is housed in the tank 8 under pressure applied from the outside via the gasket 7. This housing configuration prevents the honeycomb filter 6 from moving within the tank 8, ensuring its stability. The gasket 7 can be made of materials such as ceramic fiber.

[0044] In the range-extended electric vehicle 1, compared to a conventional vehicle that uses a gasoline engine 4 as its power source, the operation and shutdown of the gasoline engine 4 are switched more frequently. Furthermore, when the gasoline engine 4 is running, under optimal efficiency conditions, the temperature of the exhaust gas 4b tends to increase. Therefore, in the range-extended electric vehicle 1, the thermal expansion and contraction of the canister 8 housing the honeycomb filter 6 repeatedly occur, causing fluctuations in the surface pressure exerted on the honeycomb filter 6 from the canister 8. The honeycomb filter 6 is heavier than the honeycomb structure 9 (described later), and it is prone to move inside the canister 8 when the surface pressure decreases. Although considering the decrease in surface pressure caused by the thermal expansion of the canister 8, and considering setting a higher surface pressure on the honeycomb filter 6 when the canister 8 contracts, the honeycomb filter 6 may still be damaged due to the surface pressure.

[0045] In the exhaust gas purification device 5 of this embodiment, the average coefficient of thermal expansion in the radial direction orthogonal to the direction extending from the perforation 63, ranging from 40°C to 800°C, is 1.4 ppm / K or higher. Therefore, the honeycomb filter 6 can be adequately maintained in the range-extended electric vehicle 1 by maintaining it under surface pressure without damage. This is because, by constructing the honeycomb filter 6 in a manner that allows for easy expansion in the radial direction, even in cases where the surface pressure to the honeycomb filter 6 decreases due to the thermal expansion of the tank 8, the decrease in surface pressure on the honeycomb filter 6 can be suppressed. The average coefficient of thermal expansion in the radial direction orthogonal to the direction extending from the perforation 63, ranging from 40°C to 800°C, is preferably 1.6 ppm / K or higher. With a coefficient of thermal expansion of 1.6 ppm / K or higher, the honeycomb filter 6 can be reliably and adequately maintained under surface pressure without damage. Furthermore, the average coefficient of thermal expansion in the radial direction orthogonal to the direction extending from the perforation 63, ranging from 40°C to 800°C, is preferably 2.1 ppm / K or lower. By setting the concentration to below 2.1 ppm / K, excessive thermal stress can be avoided even when a temperature gradient is generated within the honeycomb filter due to temperature variations in the exhaust gas, thus preventing damage caused by thermal stress to the honeycomb filter.

[0046] The average coefficient of thermal expansion was determined according to JISR 1618 (2002). Specifically, a test piece with a width of 10 mm × thickness of 20 mm × length of 80 mm was cut from the center of the honeycomb filter 6, with the thickness direction aligned with the direction of the pores 63 and the length direction parallel to one side of the pores. The test piece did not include the sealing portion 65. The coefficient of thermal expansion was obtained by dividing the change in length of the test piece when the temperature of the test piece changed from 40°C to 800°C by the length of the test piece at 40°C. The coefficient of thermal expansion was measured for at least two test pieces, and their average value was taken as the average coefficient of thermal expansion.

[0047] Preferably, the opening ratio of the honeycomb substrate 60 is 77% or more, and the porosity of the septum 64 of the honeycomb filter 6 in the uncatalyst-supported state is preferably 60% or more, or the porosity of the septum 64 of the honeycomb filter 6 in the catalyst-supported state is 40% or more. In the range-extended electric vehicle 1, it is preferable to increase the heating rate of the honeycomb filter 6 and increase the contact area with the exhaust gas 4b, as described above, by increasing the opening ratio and porosity of the honeycomb filter 6. This is based on the view that the temperature of the honeycomb filter 6 follows the temperature of the exhaust gas 4b well, increasing the temperature of the honeycomb filter 6 promotes the combustion of soot and reduces the residual accumulation of soot. However, if the opening ratio and porosity are increased in this way, there is a tendency for the strength of the honeycomb filter 6 to decrease. In a honeycomb filter 6 with such a high opening ratio and porosity, it is particularly useful to set the average coefficient of thermal expansion to 1.4 ppm / K or more.

[0048] The aperture ratio of the honeycomb substrate 60 is defined as the ratio of the area of ​​the cross-section of the honeycomb substrate 60 orthogonal to the axial direction at the axial center position of the pores 63. The aperture ratio is determined independently of the sealing portion 65. The total area of ​​the cross-section of the honeycomb substrate 60 orthogonal to the axial direction is determined based on the shape of the honeycomb substrate 60, ignoring the presence of the pores 63. The area of ​​the pores 63 is determined based on the shape of the partition walls 64, ignoring the presence of the catalyst supported on the partition walls 64. The aperture ratio is determined by image analysis of the cross-section of the honeycomb substrate 60.

[0049] Preferably, a catalyst is supported on the partition wall 64 of the honeycomb filter 6. As the catalyst, an oxidation-promoting catalyst can be used. Examples of such catalysts include alumina supported on platinum and palladium. Three-way catalysts are also included. A three-way catalyst is a catalyst that primarily purifies hydrocarbons (HC), carbon monoxide (CO), and nitrogen oxides (NOx). Examples include catalysts containing platinum (Pt), palladium (Pd), and rhodium (Rh). With this three-way catalyst, hydrocarbons are purified into water and carbon dioxide through oxidation or reduction, carbon monoxide is purified into carbon dioxide, and nitrogen oxides are purified into nitrogen. By supporting the catalyst on the surface and within the pores of the partition wall 64, the honeycomb filter 6 also purifies gaseous components such as NOx, HC, and CO as part of the exhaust gas 4b.

[0050] The preferred pore density of the honeycomb filter 6 is 54 pores / cm². 2 The above. The pore density is 54 pores / cm². 2 The above measures can improve the strength of the honeycomb filter 6 and increase the surface pressure that prevents damage to the honeycomb filter 6. The pore density of the honeycomb filter 6 is the number of pores 63 per unit cross-sectional area, which is calculated by dividing the total number of pores 63 by the bottom area of ​​the side of the honeycomb filter 6 excluding the outer peripheral sidewall.

[0051] The septum 64 of the honeycomb filter 6 preferably contains 0.5 wt% or more of cerium. By containing 0.5 wt% or more of cerium, the average coefficient of thermal expansion in the radial direction from 40°C to 800°C can be reliably set to 1.4 ppm / K or more. To determine the cerium content in the septum 64, when a honeycomb filter 6 in its uncatalyzed state is available, at least 10 g is cut from the honeycomb filter 6, pulverized, compressed, and solidified into granular test pieces. These test pieces are then subjected to quantitative fluorescence X-ray analysis to determine the cerium content. For the honeycomb filter 6 in its catalyst-supported state, the cerium content in the substrate is quantitatively analyzed using the following method: SEM images of the test pieces, after being cut, resin-embedded, and mirror-polished, are captured. The catalyst portion and the substrate portion are then binarized and separated within a field of view equal to the thickness of the septum 64. For the substrate portion, the cerium content is quantitatively analyzed using EPMA (electron probe microanalysis).

[0052] The exhaust gas purification device 5 may also have a honeycomb structure 9 disposed upstream of the honeycomb filter 6.

[0053] The honeycomb structure 9 has a second honeycomb substrate 90. The second honeycomb substrate 90 has porous partitions 94 that divide and form a plurality of cells 93 extending from a second inflow side end face 91 to a second outflow side end face 92. The cells 93 of the second honeycomb substrate 90 are open at both ends. The honeycomb structure 9 is a flow-through type. That is, exhaust gas 4b from the second inflow side end face 91 passes through the cells 93 and is discharged from the second outflow side end face 92.

[0054] The honeycomb structure 9 can be housed together with the honeycomb filter 6 in the tank 8. The honeycomb structure 9 can be disposed in the tank 8 with its outer periphery covered by gaskets 7 (buffer material). A catalyst can be supported on the partition wall 94 of the honeycomb structure 9. The catalyst of the honeycomb structure 9 can be the same type as that of the honeycomb filter 6, or it can be different.

[0055] The following is a more detailed description of the honeycomb filter 6 and the honeycomb structure 9.

[0056] <About Cellular Filters>

[0057] like Figure 2 As shown, in the honeycomb filter 6, the honeycomb substrate 60 is a honeycomb substrate with a honeycomb shape having porous partitions 64, which divides into a plurality of pores 63 that form a flow path for fluid from the inflow side end face 61 to the outflow side end face 62. Figure 3 This is a schematic top view showing the inflow side end face 61 of the honeycomb filter 6. The shape of the honeycomb filter 6 is not limited to... Figure 4The cylindrical shape shown can be categorized into elliptical cylindrical shapes, square cylindrical shapes, and cylindrical shapes with polygonal bases, as well as cylindrical shapes with irregular bases.

[0058] Furthermore, the size of the honeycomb filter 6 is preferably such that its length along the central axis is 50 to 200 mm. Additionally, for example, if the honeycomb filter 6 is cylindrical, its bottom diameter is preferably 80 to 180 mm. If the honeycomb filter 6 is not cylindrical, its bottom area is preferably within the same range as the bottom area in the cylindrical case described above.

[0059] The average pore size of the partition wall 64 is preferably 7 to 40 μm, more preferably 8 to 35 μm. If it is less than 7 μm, the pressure loss may increase even when there is little accumulation of particulate matter. On the other hand, when it exceeds 40 μm, the honeycomb filter 6 may become brittle and easily detach, or the collection performance of particulate matter may decrease. The average pore size of the partition wall 64 is a value measured using a mercury porosimeter.

[0060] The shape of the pores 63 in the honeycomb filter 6 is not particularly limited. In the cross-section orthogonal to the central axis, polygons such as triangles, quadrilaterals, pentagons, hexagons, and octagons, circles, or ellipses are preferred, but other irregular shapes are also acceptable. A combination of quadrilaterals and octagons is also preferred. Furthermore, in the cross-section orthogonal to the direction in which the pores 63 extend, it is preferable that all the cross-sectional areas of the pores 63 are the same. However, it is also preferable that the cross-sectional area of ​​the second pore 632 with a sealing portion 65 on the inflow side end face 61 (the cross-sectional area in the cross-section orthogonal to the direction in which the pores 63 extend) is smaller than the cross-sectional area of ​​the first pore 631 with a sealing portion 65 on the outflow side end face 62 (the cross-sectional area in the cross-section orthogonal to the direction in which the pores 63 extend). If this is the case, the increase in pressure loss when capturing particulate matter in the exhaust gas 4b can be suppressed.

[0061] Furthermore, the hydraulic diameters of the cells in the honeycomb substrate 60 can all be the same, or the hydraulic diameters of the first cell 631 and the second cell 632 can be different, but it is preferable that the hydraulic diameters are different. Specifically, in the case of purifying the exhaust gas 4b of the gasoline engine 4, in order to reduce pressure loss, it is preferable that the hydraulic diameter of the second cell 632 is larger than that of the first cell 631, and preferably the hydraulic diameter of the first cell 631 is 20 to 45% of the hydraulic diameter of the second cell 632.

[0062] Alternatively, the honeycomb filter 6 may also have an outer peripheral wall located at its outermost periphery. It should be noted that the outer peripheral wall is preferably a molded integral wall formed integrally with the porous substrate during molding, but after molding, the outer periphery of the porous substrate is ground to form a predetermined shape; a cement-coated wall with an outer peripheral wall made of ceramic cement or the like is also preferred. In the case of a molded integral wall, the material of the outer peripheral wall is preferably the same as the material of the honeycomb filter 6. Furthermore, if the outer peripheral wall is a cement-coated wall, materials containing flux components such as glass added to the matrix can be used as the material for the cement-coated wall. Additionally, the thickness of the outer peripheral wall is preferably 0.5 to 1.5 mm.

[0063] The catalyst loading per unit volume in the honeycomb filter 6 can be less than the three-way catalyst loading per unit volume in the partitions 94 of the honeycomb structure 9. By adjusting the catalyst loading per unit volume in this way, the heat generated by the catalytic reaction can be increased. That is, even when using the minimum amount of catalyst (including the three-way catalyst) required for the purification of exhaust gas 4b, the catalyst (including the three-way catalyst) can be uniformly loaded in the honeycomb filter 6 and the honeycomb structure 9. However, when the ratio of the three-way catalyst loaded in the partitions 94 of the honeycomb structure 9 is increased, the heat generated by the catalytic reaction increases, and therefore the heating rate of the honeycomb structure 9 increases. Therefore, in the early stage after engine start-up, that is, in the short period of time after the engine just starts running, the catalyst (including the three-way catalyst) easily reaches the active temperature. Furthermore, the heat from the exhaust gas 4b heated by the honeycomb structure 9 can also be used to heat the honeycomb structure 9.

[0064] Specifically, the catalyst loading per unit volume in the honeycomb filter 6 is preferably 160 g / L or less, more preferably 10 to 120 g / L, and particularly preferably 20 to 100 g / L. If the loading exceeds 160 g / L, the pores formed in the partition wall 64 will be blocked by the catalyst, and the pressure loss may become too large.

[0065] The sealing portion 65 can be made of a sealing material comprising ceramic raw material, water or alcohol, and an organic binder. Preferably, the ceramic raw material is the same as that used as the raw material for the honeycomb substrate 60 (the partition wall 64 of the honeycomb substrate 60). Thus, during firing, the sealing portion 65 is firmly bonded to the partition wall 64.

[0066] The sealing section 65 is preferably configured to alternately seal the first hole grid 631 and the second hole grid 632, thereby forming a grid pattern on both end faces.

[0067] The depth of the sealing portion 65 is preferably 1 to 5 mm, more preferably 1 to 3 mm. If it is shallower than 1 mm, the strength of the sealing portion 65 may be reduced. On the other hand, if it is deeper than 5 mm, the area of ​​PM capture by the partition wall 64 may be smaller. Here, the depth of the sealing portion 65 refers to the length of the sealing portion 65 in the direction in which the pore grid 63 extends.

[0068] <About honeycomb structures>

[0069] like Figure 2 As shown, in the honeycomb structure 9 (second honeycomb substrate 90), the second honeycomb substrate 90 is a honeycomb-shaped substrate with porous partitions 94. These partitions 94 are divided into multiple cells 93 that form a flow path for fluid, extending from the second inflow side end face 91 to the second outflow side end face 92. The cells 93 formed by the honeycomb structure 9 ensure the flow path of fluid from the second inflow side end face 91 to the second outflow side end face 92 (the cells 93 are not sealed). Therefore, even if a large amount of three-way catalyst is loaded onto the partitions 94 of the honeycomb structure 9, it is difficult to impede the flow of fluid (exhaust gas 4b), and the increase in pressure loss is minimal. Therefore, it is possible to increase the loading per unit volume of the three-way catalyst. It should be noted that in the honeycomb structure 9, the loading of the three-way catalyst per unit volume can be uniform, but it is preferable that the loading of the three-way catalyst per unit volume at the end of the second inflow side end face 91 is greater than the loading of the three-way catalyst at other parts. On the other hand, if the loading of the three-way catalyst per unit volume at the end of the second inflow side end face 91 is less than the loading of the three-way catalyst at other parts, the heat generated by the catalytic reaction at the end of the fluid inflow side (the end of the second inflow side end face 91) is insufficient, and therefore the heating rate is reduced. Therefore, time is required before the catalyst's active temperature is reached, and the purification performance of the exhaust gas 4b may be insufficient. If the loading of the three-way catalyst per unit volume is greater than the loading of the three-way catalyst at other parts, the heat generated by the catalytic reaction at the end of the second inflow side end face 91 is increased compared to other parts, thus enabling a large amount of three-way catalyst to reach the catalyst active temperature in the early stages after engine start-up. Figure 5 It is a schematic representation Figure 2 The diagram shows a top view of the second inflow side end face 91 of the honeycomb structure 9. The end of the second inflow side end face 91 is defined as a range from the second inflow side end face 91 to a position where the distance from the second inflow side end face 91 is 10% to 60% of the length in the direction of the central axis of the honeycomb structure 9.

[0070] The shape of the honeycomb structure 9 is not limited to Figure 6 The cylindrical shape shown can be exemplified by elliptical cylindrical shapes, square cylindrical shapes, and cylindrical shapes with polygonal bases, as well as cylindrical shapes with irregular bases.

[0071] Specifically, the size of the honeycomb structure 9 is preferably 30~200mm in length along the central axis.

[0072] The diameter of the honeycomb structure 9 can be the same as or smaller than the diameter of the honeycomb filter 6. Preferably, the diameter of the honeycomb structure 9 is smaller than that of the honeycomb filter 6. When the diameter of the honeycomb structure 9 is smaller than that of the honeycomb filter 6, the honeycomb structure 9 is lighter than the honeycomb filter 6, provided that the length of the honeycomb structure 9 along its central axis is the same as or shorter than that of the honeycomb filter 6. Therefore, the heating rate is faster, and the honeycomb structure 9 easily reaches the catalyst activation temperature in the early stages after engine start-up. There is a limit to increasing the volume of the canister 8; therefore, reducing the size of the honeycomb structure 9 allows for a larger honeycomb filter 6. Furthermore, when the honeycomb filter 6 is larger, it can efficiently remove particulate matter from the exhaust gas 4b.

[0073] When the diameter of the honeycomb structure 9 is smaller than the diameter of the honeycomb filter 6, the diameter of the honeycomb structure 9 is preferably 50-80% of the diameter of the honeycomb filter 6, more preferably 55-75%, and even more preferably 60-70%. By setting the diameter within the above range, the honeycomb structure 9 heats up at a better rate due to the heat of the exhaust gas 4b. However, if the diameter is less than 50%, the pressure drop may become too large. On the other hand, if it exceeds 80%, even with the heat of the exhaust gas 4b, the honeycomb structure 9 may not heat up sufficiently (the heating rate becomes slower). Furthermore, for example, when the honeycomb structure 9 is cylindrical, the diameter of its bottom surface is preferably 80-180 mm. When the honeycomb structure 9 is not cylindrical, the area of ​​its bottom surface is preferably in the same range as the area of ​​the bottom surface in the cylindrical case described above.

[0074] The diameter of the honeycomb structure 9 and the honeycomb filter 6 is defined as the length of a line segment in a plane orthogonal to the central axis, passing through the central axis and with both ends located on the outer edges of the honeycomb structure 9 and the honeycomb filter 6, and is measured by a laser length measuring instrument.

[0075] The thickness of the partition wall 94 is preferably 50.8 to 101.6 μm, more preferably 50.8 to 75 μm, and particularly preferably 65 to 75 μm. If it is less than 50.8 μm, the strength of the honeycomb structure 9 may decrease. On the other hand, if it exceeds 101.6 μm, the pressure loss when the exhaust gas 4b passes through the pores 93 may increase. The thickness of the partition wall 94 is determined by observing a cross-section parallel to the central axis under a microscope.

[0076] The pore density of the honeycomb structure 9 can be greater than that of the honeycomb substrate 60. Furthermore, the aperture ratio of the second honeycomb substrate 90 of the honeycomb structure 9 can be greater than that of the honeycomb substrate 60 of the honeycomb filter 6. Thus, with a higher pore density and aperture ratio, the partition walls 94 of the honeycomb structure 9 are thinner than the partition walls 64 of the honeycomb filter 6. Therefore, when the honeycomb structure 9 and the honeycomb filter 6 have the same volume, or when the volume of the honeycomb structure 9 is smaller than that of the honeycomb filter 6, the honeycomb structure 9 is lighter than the honeycomb filter 6, and thus the honeycomb structure 9 can more easily reach the catalyst activation temperature in the early stages after engine start-up.

[0077] The opening ratio of the second honeycomb substrate 90 of the honeycomb structure 9 can be larger than that of the honeycomb substrate 60 of the honeycomb filter 6. However, in this case, it is preferable that the porosity of the partition wall 94 of the second honeycomb substrate 90 is smaller than that of the partition wall 64 of the honeycomb substrate 60. If the porosity of the partition wall 94 is smaller than that of the partition wall 64, the strength of the honeycomb structure 9 can be ensured. That is, when the opening ratio of the second honeycomb substrate 90 of the honeycomb structure 9 is larger than that of the honeycomb substrate 60 of the honeycomb filter 6, the heat capacity of the honeycomb structure 9 is smaller than that of the honeycomb filter 6, and therefore the honeycomb structure 9 heats up faster than the honeycomb filter 6. However, the strength of the honeycomb structure 9 may be insufficient. Therefore, it is preferable that the porosity of the partition wall 94 is smaller than that of the partition wall 64. Furthermore, since the honeycomb structure 9 heats up in the early stage, the heat of the exhaust gas 4b can be used to heat up the honeycomb structure 9. That is, the honeycomb filter 6 can be heated up rapidly.

[0078] The average pore size of the partition wall 94 is preferably 5 to 30 μm, more preferably 10 to 25 μm. If it is less than 5 μm, sufficient adhesion between the catalyst layer and the surface of the partition wall 94 cannot be achieved when forming a catalyst layer by supporting a three-way catalyst on the partition wall 94, and the catalyst layer may peel off. On the other hand, if it exceeds 30 μm, the honeycomb structure 9 may become brittle and easily detach. The average pore size of the partition wall 94 is a value measured using a mercury porosimeter.

[0079] The shape of the cells 93 in the honeycomb structure 9 is not particularly limited. In a cross-section orthogonal to the central axis, the preferred shapes are polygons such as triangles, quadrilaterals, pentagons, hexagons, and octagons, circles, or ellipses. Other irregular shapes are also acceptable. A combination of quadrilaterals and octagons is also a preferred option.

[0080] Furthermore, the hydraulic diameters of all the cells in the honeycomb structure 9 can be the same, and the hydraulic diameters of the cells 93 opening at the second inflow side end face 91 and the cells 93 opening at the second outflow side end face 92 can also be different. Any of the above is acceptable, but it is preferred that the hydraulic diameters are different. Specifically, in the case of purifying the exhaust gas 4b of the gasoline engine 4, in order to reduce pressure loss, it is preferable that the hydraulic diameter of the cells 93 opening at the second outflow side end face 92 is larger than the hydraulic diameter of the cells 93 opening at the second inflow side end face 91. The hydraulic diameter of the cells 93 opening at the second inflow side end face 91 is preferably 20-45% of the hydraulic diameter of the cells 93 opening at the second outflow side end face 92. In this specification, the "hydraulic diameter of the cell" is a value calculated using the formula "4 × (cross-sectional area) / (perimeter)". Here, "cross-sectional area" refers to the area of ​​the cells in a cross-section orthogonal to the direction in which the cells extend, and "perimeter" refers to the "length of the outer perimeter of the cells" in a cross-section orthogonal to the direction in which the cells extend.

[0081] The partitions 94 of the honeycomb structure 9 are primarily composed of ceramic. Specifically, the material of the partitions 94 is preferably selected from at least one of the following groups: silicon carbide, silicon-silicon carbide composite materials, cordierite, mullite, alumina, spinel, silicon carbide-cordierite composite materials, lithium aluminum silicate, and aluminum titanate. Cordierite, with its low coefficient of thermal expansion and excellent thermal shock resistance, is particularly preferred. Furthermore, when referring to "primarily composed of ceramic," it means containing at least 90% by mass of ceramic.

[0082] Alternatively, the honeycomb structure 9 may also have an outer peripheral wall located at its outermost periphery. Preferably, the outer peripheral wall is a molded integral wall formed integrally with the porous substrate during molding, but after molding, the outer periphery of the porous substrate is ground to form a predetermined shape; a cement-coated wall with an outer peripheral wall made of ceramic cement or the like is also preferred. In the case of a molded integral wall, the material of the outer peripheral wall is preferably the same as the material of the honeycomb structure 9. Alternatively, if the outer peripheral wall is a cement-coated wall, materials containing flux components such as glass added to the matrix can be used as materials for the cement-coated wall. Furthermore, the thickness of the outer peripheral wall is preferably 0.5 to 1.5 mm.

[0083] The loading of the three-way catalyst supported on the honeycomb structure 9 is preferably 200-400 g / L, more preferably 200-300 g / L, and particularly preferably 200-250 g / L. If the loading is less than 200 g / L, the amount of three-way catalyst is too small, resulting in insufficient heat generated by the catalytic reaction, which may make it difficult to heat up to the active temperature of the three-way catalyst in the early stages after engine start-up. If it exceeds 400 g / L, the loading per unit volume is too large, narrowing the flow path of the pores 93 with openings at both ends, which may increase pressure loss.

[0084] <Manufacturing Method of Waste Gas Purification Device>

[0085] Next, the manufacturing method of the exhaust gas purification device of this utility model will be described. The manufacturing method of the exhaust gas purification device of this utility model is not particularly limited; for example, the following methods can be cited.

[0086] The manufacturing method comprises the following steps:

[0087] In the honeycomb structure forming process, a second honeycomb molded body with porous partitions is fired to obtain a second honeycomb substrate. The porous partitions are divided into multiple pores that form a flow path for fluid, extending from the second inflow side end face to the second outflow side end face. A catalyst slurry containing a ternary catalyst flows into the multiple pores from the second inflow side end face of the second honeycomb substrate. The catalyst slurry (supporting the ternary catalyst) is coated on the partition surface of the multiple pores to form a honeycomb structure.

[0088] In the honeycomb filter forming process, the openings of predetermined cells in one end face of a honeycomb molded body and the openings of remaining cells in the other end face are sealed, followed by firing to form a honeycomb filter. The honeycomb molded body has a porous partition wall that divides multiple cells into flow paths extending from the inflow side end face to the outflow side end face, forming a fluid flow path. The honeycomb filter has a honeycomb substrate, and sealing portions are provided at the openings of predetermined cells in the inflow side end face and the openings of remaining cells in the outflow side end face of the honeycomb substrate.

[0089] In the assembly process, a honeycomb structure is arranged on the inlet side of the tank, which has an inlet for the inflow of exhaust gas and an outlet for the outflow of purified exhaust gas, with the second inflow side end face facing the inlet side of the tank. Furthermore, a honeycomb filter is arranged on the outlet side of the tank, with the outflow side end face facing the outlet side of the tank. The honeycomb structure and the honeycomb filter are then housed within the tank.

[0090] As a honeycomb structure formed in the honeycomb structure forming process, the ratio of the length of the honeycomb structure in the central axis direction to the length of the honeycomb filter in the central axis direction is 0.1 to 0.5. The pore density of the second honeycomb substrate constituting the honeycomb structure is greater than that of the honeycomb substrate constituting the honeycomb filter, and the opening ratio of the second honeycomb substrate constituting the honeycomb structure is greater than that of the honeycomb substrate constituting the honeycomb filter. The diameter of the honeycomb structure is the same as or smaller than the diameter of the honeycomb filter. As a honeycomb filter formed in the honeycomb filter forming process, it does not support a catalyst, or supports a catalyst and the catalyst loading per unit volume is less than the catalyst loading per unit volume of the ternary catalyst supported in the honeycomb structure. Through the above processes, the exhaust gas purification device of this utility model can be manufactured.

[0091] <About the honeycomb structure formation process>

[0092] The second honeycomb substrate used in the formation process of the honeycomb structure can be manufactured as follows: First, the molding raw materials are mixed to form a blank. Next, the obtained blank is extruded and molded into a honeycomb shape to obtain a second honeycomb molded body. Then, by firing the obtained second honeycomb molded body, the second honeycomb substrate can be obtained.

[0093] The preferred molding raw material is a ceramic raw material with added dispersion medium and additives. Examples of additives include organic binders, pore-forming materials, and surfactants. Examples of dispersion mediums include water.

[0094] As a ceramic raw material, it is preferably selected from at least one of the following groups: silicon carbide, silicon-silicon carbide composite materials, cordierite raw materials, mullite, alumina, spinel, silicon carbide-cordierite composite materials, lithium aluminum silicate, and aluminum titanate. Among them, cordierite raw materials with low coefficient of thermal expansion and excellent thermal shock resistance are preferred. The content of ceramic raw material relative to the total mass of molding raw materials is preferably 80-95%.

[0095] Examples of organic binders include methylcellulose, hydroxypropyl methylcellulose, hydroxyethyl cellulose, carboxymethyl cellulose, and polyvinyl alcohol. Methylcellulose and hydroxypropyl methylcellulose are preferably used in combination. The binder content relative to the total molding raw material is preferably 1-10% by mass. One type can be used alone, or two or more can be used in combination.

[0096] As a pore-forming material, there are no particular limitations on any material that becomes porous after firing; examples include starch, foaming resin, water-absorbing resin, and silicone. The content of the pore-forming material relative to the total molding raw material is preferably 0-20% by mass. One type can be used alone, or two or more can be used in combination.

[0097] Surfactants such as ethylene glycol, dextrin, fatty acid soaps, and polyols can be used. They can be used individually or in combination of two or more. The surfactant content relative to the total molding raw material is preferably 0.1-5% by mass.

[0098] The content of the dispersion medium is preferably 0.1 to 5% by mass relative to the total mass of the molding raw material.

[0099] By adjusting the particle size and proportion of the ceramic raw materials (aggregate particles) used, as well as the particle size and proportion of the added pore-forming materials, a porous substrate with the desired porosity and average fine pore size can be obtained.

[0100] There are no particular limitations on the method of mixing raw materials to form blanks; for example, methods such as using a kneader or a vacuum ply mill can be used. Extrusion molding can be performed using a die with the desired pore shape, septum thickness, and pore density. As for the die material, a wear-resistant, ultra-hard alloy is preferred.

[0101] The firing temperature can be appropriately determined based on the material of the second honeycomb molded body. For example, if the material of the first honeycomb molded body is cordierite, the firing temperature is preferably 1380~1450℃, more preferably 1400~1440℃. In addition, the firing time is preferably set to about 3~10 hours.

[0102] It should be noted that the second honeycomb molded body can also be dried before firing. The drying method is not particularly limited; examples include hot air drying, microwave drying, dielectric drying, reduced pressure drying, vacuum drying, and freeze drying. Dielectric drying, microwave drying, or hot air drying are preferred, either alone or in combination. Furthermore, as drying conditions, a drying temperature of 30–150°C and a drying time of 1 minute to 2 hours are preferred.

[0103] Next, the method for coating the catalyst slurry (supported by a three-way catalyst) is not particularly limited, and known methods can be used. For example, firstly, a catalyst slurry containing a three-way catalyst is prepared. Then, the catalyst slurry is poured into the pores by impregnation or suction. Preferably, the catalyst slurry is coated on the entire surface of the partition walls within the pores. Then, after the catalyst slurry has poured into the pores, the remaining slurry is blown away with compressed air. Then, by drying and sintering the catalyst slurry, a honeycomb structure with the three-way catalyst supported on the surface of the partition walls within the pores can be obtained. The drying conditions are preferably set to 80-150°C for 1-6 hours. The sintering conditions are preferably set to 450-700°C for 0.5-6 hours. It should be noted that, as components other than the catalyst contained in the catalyst slurry, alumina and the like can be cited.

[0104] <About the honeycomb filter forming process>

[0105] The second honeycomb molded body used in the honeycomb filter forming process can be manufactured as follows: The clay is extruded into a honeycomb shape in a manner that satisfies the following conditions to obtain the second honeycomb molded body.

[0106] In the extrusion molding process of this step, the blank extruded from the die is cut off such that the ratio of the length of the honeycomb structure in the central axis direction to the length of the honeycomb filter in the central axis direction is 0.1 to 0.5. Furthermore, a die is used in which the pore density of the first honeycomb substrate of the honeycomb structure is greater than the pore density of the second honeycomb substrate of the honeycomb filter, the opening ratio of the second honeycomb substrate of the honeycomb structure is greater than the opening ratio of the honeycomb substrate of the honeycomb filter, and consequently the diameter of the honeycomb structure is the same as or smaller than the diameter of the honeycomb filter.

[0107] One method for sealing the openings of the cells in a honeycomb molded body is to fill the openings with a sealing material. Specifically, this method involves applying a mask to one end face of the honeycomb molded body to block the openings of predetermined cells. There are no particular limitations on the method of applying the mask; it is preferable to alternately seal the openings of predetermined cells on the outflow side end face and the openings of remaining cells on the inflow side end face of the honeycomb substrate, applying the mask in a grid pattern on both end faces. Then, a slurry-like sealing material comprising a ceramic raw material, water or alcohol, and an organic binder is pre-stored in a storage container. The ceramic raw material is preferably the same as the raw material used for the honeycomb molded body. The ceramic raw material is preferably 70-90% by mass of the total sealing material. Water or alcohol is preferably 10-30% by mass of the total sealing material, and the organic binder is preferably 0.1-2.0% by mass of the total sealing material. Examples of organic binders include hydroxypropyl methylcellulose and methylcellulose. Then, the end with the mask applied is immersed in a storage container, and sealing material is filled into the openings of the unmasked pores to form a sealed portion. The viscosity of the sealing material is preferably 600~1200 Pa·s. It should be noted that the viscosity of the sealing material is a value measured at 30°C using a rotary viscometer at a rotational speed of 30 rpm.

[0108] Then, a mask is applied to the other end face of the honeycomb molded body to block the openings of the remaining cells. Afterwards, the masked end face is immersed in a storage container containing a slurry-like sealing material, and the sealing material is filled into the openings of the unmasked cells to form sealing portions. In this way, a honeycomb filter molded body can be obtained in which the openings of predetermined cells on one end face and the openings of the remaining cells on the other end face are equipped with sealing portions.

[0109] The firing temperature for firing the honeycomb filter molded body can be appropriately determined according to the material of the honeycomb filter molded body. For example, when the material of the honeycomb filter molded body is cordierite, the firing temperature is preferably 1380~1450℃, more preferably 1400~1440℃. In addition, the firing time is preferably set to about 3~10 hours.

[0110] It should be noted that the honeycomb filter molded body can also be dried before firing. The drying method is not particularly limited; examples include hot air drying, microwave drying, dielectric drying, reduced pressure drying, vacuum drying, and freeze drying. Dielectric drying, microwave drying, or hot air drying are preferred, either alone or in combination. Furthermore, as drying conditions, a drying temperature of 30–150°C and a drying time of 1 minute to 2 hours are preferred.

[0111] It should be noted that the honeycomb molded body can also be fired before the sealing part is formed to obtain a fired honeycomb body. After the opening of the predetermined cell in one end face and the opening of the remaining cell in the other end face are sealed, the honeycomb filter is further fired to obtain a honeycomb filter.

[0112] It should be noted that a honeycomb filter can be obtained by coating a honeycomb filter structure with a catalyst slurry (catalyst-supported) using a known method. For example, the method of coating the catalyst slurry involves first preparing a catalyst slurry containing a ternary catalyst. Then, the prepared catalyst slurry is allowed to flow into the pores through impregnation and suction. Preferably, the catalyst slurry is coated on the entire surface of the partition walls within the pores. After the catalyst slurry has flowed into the pores, any remaining slurry is blown away with compressed air. Then, by drying and sintering the catalyst slurry, a sealed honeycomb structure with the catalyst loaded on the surface of the partition walls within the pores can be obtained. The drying conditions are preferably set to 80–150°C for 1–6 hours. The sintering conditions are preferably set to 450–700°C for 0.5–6 hours. It should be noted that, as components other than the catalyst contained in the catalyst slurry, alumina and the like can be examples.

[0113] <About the assembly process>

[0114] In the assembly process, after covering the outer periphery of the honeycomb structure and the honeycomb filter with gaskets (cushioning material), the gasket-covered honeycomb structure and the honeycomb filter are placed inside the tank. At this time, the honeycomb structure and the honeycomb filter are preferably housed in a compressed state within the tank. Examples of gaskets include ceramic fiber gaskets. This prevents the honeycomb structure and the honeycomb filter from moving within the tank.

[0115] The tank body can use conventionally known tank bodies, for example, it can be manufactured by stamping and welding sheet material made of ferrite-based stainless steel. Specifically, the diameter of the inlet of the tank body is preferably 30 to 80 mm, and the diameter of the outlet is preferably 30 to 80 mm.

[0116] The preferred embodiments of the present invention have been described in detail above with reference to the accompanying drawings, but the present invention is not limited to these examples. Obviously, anyone with general knowledge in the technical field to which this invention pertains can conceive of various modifications or alterations within the scope of the technical concept described in the claims, and these modifications are naturally understood to fall within the technical scope of this invention.

[0117] Example

[0118] The present invention will be described in more detail below through embodiments. The present invention is not limited to these embodiments.

[0119] (Example 1)

[0120] [Fabrication of Honeycomb Structures] (Honeycomb Structure Formation Process)

[0121] First, as raw materials for cordierite petrochemicals, alumina, aluminum hydroxide, kaolin, talc, and silica are used. 35 parts by weight of a dispersion medium, 6 parts by weight of an organic binder, and 0.5 parts by weight of a dispersant are added to 100 parts by weight of the cordierite petrochemical raw materials, and the mixture is then mixed and kneaded to prepare raw clay. Water is used as the dispersion medium, hydroxypropyl methylcellulose as the organic binder, and ethylene glycol as the dispersant.

[0122] Next, the clay is extruded using a predetermined mold to form a honeycomb structure with quadrilateral pores and an overall cylindrical shape. The honeycomb structure is then dried using a microwave dryer, followed by a hot air dryer to ensure complete drying. The two ends of the honeycomb structure are then cut off and adjusted to predetermined dimensions. Finally, it is fired at 1410-1440°C for 5 hours to obtain a fired honeycomb structure.

[0123] Next, a mixture of γAl₂O₃ particles with an average particle size of 100 μm and CeO₂ particles with an average particle size of 100 μm (specific surface area 50 m²) was prepared. 2 / g) was wet-milled using a ball mill to obtain broken particles with an average particle size of 5 μm. The obtained broken particles were impregnated in a solution containing Pt and Rh, so that Pt and Rh were loaded into the pores of the broken particles. Then, acetic acid and water were added to the broken particles loaded with Pt and Rh to obtain a coating slurry. The inflow-side end of the prepared honeycomb sintered body was impregnated in the obtained coating slurry. Then, with the inflow-side end impregnated, the coating slurry was vacuum-suctioned from the outflow-side end face of the honeycomb sintered body, thereby coating the slurry onto the partition wall of the honeycomb sintered body to form a catalyst layer. Then, it was dried and calcined at 600°C for 3 hours to produce a honeycomb structure.

[0124] The fabricated honeycomb structure has a diameter (D) of 120 mm, a length (L) along the central axis of 70 mm, a partition thickness of 0.05 mm, and a cell density of 750 cpsi (116 cells / cm²). 2 The second honeycomb substrate has an opening rate of 88%, a pore rate of 55% in the partition wall, and a coating amount (WC) of 150 g / L for the three-way catalyst support.

[0125] [Cellular Filter Fabrication] (Cellular Filter Formation Process)

[0126] First, alumina, aluminum hydroxide, kaolin, talc, and silica are used as cordierite raw materials. To 100 parts by weight of the cordierite raw materials, 13 parts by weight of a pore-forming material, 35 parts by weight of a dispersion medium, 6 parts by weight of an organic binder, and 0.5 parts by weight of a dispersant are added, and the mixture is then stirred and kneaded to prepare the clay. Water is used as the dispersion medium, coke with an average particle size of 1-10 μm is used as the pore-forming material, hydroxypropyl methylcellulose is used as the organic binder, and ethylene glycol is used as the dispersant. Foaming resins, water-absorbing resins, etc., can also be used as the pore-forming material. By appropriately controlling the particle size and amount of the pore-forming material, the fine pore size and porosity of the partition wall can be controlled.

[0127] Next, the clay is extruded and shaped using a pre-designed mold to obtain a honeycomb structure with quadrilateral pores and a cylindrical overall shape.

[0128] The honeycomb molded body is dried using a microwave dryer, and then completely dried using a hot air dryer. Both ends of the honeycomb molded body are then cut off and adjusted to predetermined dimensions. Next, a mask is applied to the openings of a portion of the cells on one end face of the honeycomb molded body. The masked end is then immersed in a sealing slurry containing cordierite. For the other end, a mask is applied to the openings of the cells sealed on the aforementioned end. Then, by immersing the end face in the sealing slurry, the sealing slurry is filled into the openings of the predetermined cells on one end face in a grid pattern, alternating between the openings of the predetermined cells on one end face and the openings of the remaining cells on the other end face. The honeycomb molded body filled with sealing slurry is then dried using a hot air dryer, and subsequently fired at 1410–1440°C for 5 hours, thereby producing a honeycomb filter.

[0129] The fabricated honeycomb filter has a diameter (D) of 120 mm, a length (L) along the central axis of 80 mm, and a pore density of 420 cpsi (65 pores / cm²). 2The cell spacing is 1.24 mm, the opening rate of the honeycomb substrate is 80%, the porosity of the partition wall in the unsupported state (catalyst unsupported state) is 65%, the porosity of the partition wall in the supported state (catalyst supported state) is 44%, the coating amount (WC amount) of the three-way catalyst carrier is 80 g / L, the cerium content in the partition wall is 3.0 wt%, and the average thermal expansion coefficient in the radial direction from 40℃ to 800℃ is 2.0 ppm / K.

[0130] The fabricated honeycomb structure and honeycomb filter are housed within a single metal container with an inlet and an outlet, and equipped with a pair of 2mm thick partitions. During installation, gaskets primarily composed of ceramic fibers are used to cover the outer periphery of the honeycomb structure and honeycomb filter, which are then pressed into the container and secured. This creates an exhaust gas purification device. This exhaust gas purification device is then installed in a range-extended electric vehicle (REEV) equipped with a 1500cc gasoline engine.

[0131] For the manufactured exhaust gas purification device, the "filter retention at high temperatures" and "residual buildup of the filter" are evaluated using the following methods.

[0132] [Evaluation method for filter retention at high temperatures]

[0133] With a gas flow rate of 5 Nm 3 The gas inlet temperature is generated at 100°C for 5 minutes and 800°C for 5 minutes in the gas burner device. While the gas temperature is varied, a vibration of 30G and 100 Hz is applied to the filter axis for 8 hours. Afterwards, a filter axial position deviation of less than 0.5mm is classified as "Good", a deviation of 1mm as "Acceptable", and a deviation exceeding 1mm as "Unacceptable". "Good" and "Acceptable" are then designated as qualified.

[0134] [Methods for evaluating the amount of residual buildup in filters]

[0135] An exhaust gas purification device was installed on a 2L gasoline engine vehicle. The vehicle was run three times on a chassis dynamometer in WLTC operating mode to investigate the change in soot accumulation before and after the operation. An increase in soot accumulation of less than 0.25 g / L was designated "Excellent," less than 0.5 g / L was designated "Good," and an increase exceeding 0.5 g / L was designated "NG." "Excellent" and "Good" were considered acceptable.

[0136] [Evaluation methods for the thermal shock resistance of filters]

[0137] The filter was mounted to the metal housing via an outer ceramic gasket in the same configuration as that used in vehicles, and connected to the gas burner test apparatus at a gas flow rate of 3 Nm³. 3 The filter inlet gas temperature was cycled 12 times per minute at 100℃ for 5 minutes and 900℃ for 5 minutes. A case where no cracks caused by thermal stress appeared after the test was classified as "Good"; a case where microcracks smaller than 5 mm appeared but were not practically problematic was classified as "Acceptable"; and a case where cracks larger than 5 mm appeared was classified as "Unacceptable". "Good" and "Acceptable" were then classified as "Qualified".

[0138] A case where neither the filter retention at high temperature nor the residual buildup of the filter is acceptable is judged as "OK" (acceptable), and a case where either the filter retention at high temperature or the residual buildup of the filter is unacceptable is judged as "NG" (unacceptable).

[0139] (Example 2)

[0140] Example 2 is the same as Example 1 except that the cerium content of the filter substrate is changed to 1.5 wt%.

[0141] (Example 3)

[0142] Example 3 is the same as Example 1 except that the cerium content of the filter substrate is changed to 0.5 wt%.

[0143] (Example 4)

[0144] Example 4 is the same as Example 2 except that the partition thickness is changed to 0.14 mm and the porosity of the filter substrate is changed to 63%.

[0145] (Example 5)

[0146] Example 5 is the same as Example 4 except that the porosity of the filter substrate is changed to 60%.

[0147] (Example 6)

[0148] Example 6 is the same as Example 4 except that the thickness of the filter partition is changed to 0.15 mm and the porosity of the filter substrate is set to 62%.

[0149] (Example 7)

[0150] In Example 7, the cerium content of the filter substrate was changed to 2.0 wt%, and the pore density was changed to 68 pores / cm². 2 The porosity of the filter substrate was changed to 65%, otherwise it was the same as in Example 1.

[0151] (Example 8)

[0152] Example 8 changed the pore density to 54 pores / cm² 2 Except for that, it is the same as in Example 7.

[0153] (Example 9)

[0154] Example 9, except that the pore density was changed to 56 pores / cm² 2 Except for the above, it is the same as in Example 6.

[0155] (Example 10)

[0156] Example 10 is the same as Example 9 except that the partition thickness is changed to 0.19 mm.

[0157] (Example 11)

[0158] Example 11 is the same as Example 9 except that the porosity of the filter substrate is changed to 58%.

[0159] (Example 12)

[0160] Example 12 changed the pore density to 51 pores / cm² 2 Except for that, it is the same as in Example 9.

[0161] (Example 13)

[0162] Example 13 is the same as Example 1 except that the Ce content is changed to 3.1 wt%.

[0163] (Comparative Example 1)

[0164] Comparative Example 1 is the same as Example 9 except that the cerium content of the filter substrate is changed to 0 wt%.

[0165] (Comparative Example 2)

[0166] Comparative Example 2 is the same as Example 9 except that the cerium content of the filter substrate is changed to 0.2 wt%.

[0167] [Table 1]

[0168]

[0169] Examples 1 to 13 are examples where the average coefficient of thermal expansion in the radial direction from 40°C to 800°C is 1.4 ppm / K or higher, and the filter retention performance at high temperatures is evaluated as good or acceptable. In contrast, Comparative Examples 1 and 2 are examples where the average coefficient of thermal expansion in the radial direction from 40°C to 800°C is less than 1.4 ppm / K, and the filter retention performance at high temperatures is evaluated as unacceptable. These results show that by ensuring the average coefficient of thermal expansion in the radial direction from 40°C to 800°C is 1.4 ppm / K or higher, the honeycomb filter can be adequately retained in extended-range electric vehicles under surface pressure without damage.

[0170] Figure 7 This is a graph showing the relationship between the cerium content in the partition walls of the honeycomb filters in the embodiments and comparative examples and the average radial coefficient of thermal expansion. For example... Figure 7 As shown, it was found that the radial average coefficient of thermal expansion tends to increase with the increase of cerium content in the septum of the honeycomb filter. In Examples 1-13, the cerium content in the septum of the honeycomb filter was 0.5 wt% or more, while in the comparative example, the cerium content in the septum was less than 0.5 wt%. It can be seen that by using a cerium content of 0.5 wt% or more in the septum as in Examples 1-13, it is more reliable to achieve a radial average coefficient of thermal expansion of 1.4 ppm / K or more at 40°C to 800°C.

[0171] In Examples 1-13, Examples 1, 2, 4-8, 10, and 13 are examples where the average coefficient of thermal expansion in the radial direction from 40°C to 800°C is 1.6 ppm / K or higher, and the filter retention performance at high temperatures is evaluated as good. From these results, it can be seen that by making the average coefficient of thermal expansion in the radial direction from 40°C to 800°C 1.6 ppm / K or higher, the honeycomb filter 6 can be more reliably and adequately retained under surface pressure without damage.

[0172] In Examples 1-12, Examples 1-9, 12, and 13 are examples where the honeycomb substrate of the honeycomb filter has an opening ratio of 77% or more, the pore size of the honeycomb filter in the uncatalyst-supported state has a porosity of 60% or more, or the pore size of the honeycomb filter in the catalyst-supported state has a porosity of 40% or more. In Examples 1-9 and 12, the residual ash content of the filter was evaluated as good. These results indicate that by reducing the heat capacity to meet these opening ratios and porosities, the filter exhibits good temperature rise characteristics, promotes soot combustion, and keeps the residual soot content within acceptable limits.

[0173] In Examples 1-12, Examples 1-11 and 13 show a honeycomb filter with a pore density of 54 pores / cm². 2The above example can withstand a surface pressure of 1.0 MPa, so the surface pressure will be kept above 1.0 MPa.

Claims

1. An exhaust gas purification device for a range-extended electric vehicle, wherein the range-extended electric vehicle has a gasoline engine as a range extender for charging a battery, characterized in that, The waste gas purification device has the following features: A honeycomb filter has a honeycomb substrate and a sealing portion, wherein the honeycomb substrate has a porous partition wall that divides into multiple pores extending from an inflow side end face to an outflow side end face; The sealing portion seals the pores on the inflow side end face or the outflow side end face respectively; the pores of the honeycomb substrate include a first pore that opens on the inflow side end face and is sealed on the outflow side end face, and a second pore that opens on the outflow side end face and is sealed on the inflow side end face; A gasket wound around the outer periphery of the honeycomb filter; as well as The honeycomb filter and the gasket are housed in an internal metal canister. The average coefficient of thermal expansion in the radial direction orthogonal to the direction of the extension of the lattice is above 1.4 ppm / K at 40°C to 800°C.

2. The waste gas purification device according to claim 1, wherein, The average coefficient of thermal expansion in the radial direction orthogonal to the direction of the extension of the lattice is less than 2.1 ppm / K at 40°C to 800°C.

3. The waste gas purification device according to claim 1, wherein, The opening ratio of the honeycomb substrate is 77% or higher. The porosity of the partition wall of the honeycomb filter in the uncatalyst-free state is 60% or more, or the porosity of the partition wall of the honeycomb filter in the catalyst-supported state is 40% or more.

4. The waste gas purification device according to any one of claims 1 to 3, wherein, The pore density of the honeycomb filter is 54 pores / cm². 2 above.

5. The waste gas purification device according to any one of claims 1 to 3, wherein, The septum of the cellular filter contains more than 0.5 wt% cerium.

6. The waste gas purification device according to any one of claims 1 to 3, wherein, The average coefficient of thermal expansion in the radial direction orthogonal to the direction of the extension of the pores, from 40°C to 800°C, is above 1.6 ppm / K.

7. The waste gas purification device according to any one of claims 1 to 3, wherein, The exhaust gas purification device also includes a honeycomb structure disposed upstream of the honeycomb filter. The honeycomb structure has a second honeycomb substrate, which has a porous partition wall that divides into a plurality of pores extending from a second inflow side end face to a second outflow side end face. The two ends of the pores of the second honeycomb substrate are open.

Images