Exhaust gas purification device and electric vehicle

Abstract

The utility model provides a kind of waste gas purification device and electric vehicle, can make honeycomb structure warm earlier.Waste gas purification device is the waste gas purification device (5) of electric vehicle with engine and the motor of the power source for driving, it is characterized in that, have: honeycomb structure (6), the compartment (63) of the first honeycomb substrate (60) both ends open;And honeycomb filter (7), including the first compartment (731) of the compartment (73) of second honeycomb substrate (70) in second outflow side end face (72) is sealed hole and the second compartment (732) in second inflow side end face (71) is sealed hole, honeycomb structure is configured in the upstream of honeycomb filter in the flow direction of waste gas, in at least one of honeycomb structure, honeycomb filter and between honeycomb structure and honeycomb filter, setting reduces the radiation heat reduction mechanism (8) of the transfer of heat caused by the radiation from honeycomb structure to honeycomb filter.

Description

Technical Field

[0001] This utility model relates to an exhaust gas purification device for electric vehicles and an electric vehicle equipped with the exhaust gas purification device. Background Technology

[0002] To address stringent vehicle emissions regulations, it is desirable to ensure early catalyst warm-up during engine startup and to maintain catalyst temperature even under low exhaust temperatures after engine load decreases following initial catalytic warm-up. Regarding exhaust purification, catalysts are needed to remove NOx, HC, and CO, as well as particulate matter generated during fuel combustion. Furthermore, the need to suppress CO2 emissions is increasing, leading to the widespread adoption of electric vehicles with engines (internal combustion engines) and motors as power sources. Engines serve as power sources for both driving and / or power generation. In such electric vehicles, the engine starts and stops frequently, thus requiring high levels of early start-up temperature and excellent catalyst insulation during shutdown.

[0003] Patent Document 1 discloses an exhaust gas purification device that is not specifically designed for electric vehicles, but rather comprises a honeycomb structure (honeycomb catalyst body) and a honeycomb filter (sealed honeycomb structure) arranged in series. A three-way catalyst is supported in both the honeycomb structure and the honeycomb filter. In Patent Document 1, the honeycomb structure is smaller than the honeycomb filter (specifically, the ratio of the length of the honeycomb structure to the length of the honeycomb filter is 0.1 to 0.5). This reduction in the size of the honeycomb structure allows for earlier temperature rise.

[0004] Although not specifically designed for electric vehicles, Patent Document 2 discloses an exhaust gas purification device in which a honeycomb structure (honeycomb catalyst body) and a honeycomb filter are arranged in series. A three-way catalyst is supported in the honeycomb structure, and an oxidation catalyst for removing soot is supported in the honeycomb filter. In Patent Document 2, the honeycomb structure is larger than the honeycomb filter (specifically, the length of the honeycomb structure is 2.0 to 10.0 times the length of the honeycomb filter). By increasing the size of the honeycomb structure, the amount of catalyst within it can be increased, thereby improving the exhaust gas purification performance.

[0005] Existing technical documents

[0006] Patent documents

[0007] Patent Document 1: Japanese Patent Application Publication No. 2011-167581

[0008] Patent Document 2: Japanese Patent Application Publication No. 2011-169155 Utility Model Content

[0009] The problem to be solved by the utility model

[0010] Patent documents 1 and 2 do not take into account heat transfer caused by radiation from the honeycomb structure to the honeycomb filter. If heat is transferred from the honeycomb structure to the honeycomb filter, the temperature rise of the honeycomb structure is slower. That is, in conventional structures, there is room for improvement in the temperature rise of the honeycomb structure.

[0011] This invention was developed to address the aforementioned problems, and one of its objectives is to provide an exhaust gas purification device and an electric vehicle that can heat up a honeycomb structure earlier.

[0012] Solution for solving the problem

[0013] [1] The first aspect of this utility model relates to an exhaust gas purification device for an electric vehicle having an engine and a motor as a power source for driving, characterized in that it comprises: a honeycomb structure having a first honeycomb substrate having a porous partition wall dividing a plurality of compartments extending from a first inflow side end face to a first outflow side end face, the compartments of the first honeycomb substrate being open at both ends; and a honeycomb filter having a second honeycomb substrate having a porous partition wall dividing a plurality of compartments extending from a second inflow side end face to a second outflow side end face, the compartments of the second honeycomb substrate including a first compartment and a second compartment, the first compartment being open at the second inflow side end face and sealed at the second outflow side end face, the second honeycomb substrate having ... second honeycomb substrate having a first compartment and a second compartment, the second honeycomb substrate having a first compartment and a second compartment, the second honeycomb substrate having a first compartment and a second compartment, the second honeycomb substrate having a first compartment and a second compartment, the second honeycomb substrate having a first compartment and a second compartment, the second honeycomb substrate having a first compartment and a second compartment, the second honeycomb substrate having a first compartment and a second compartment, the second honeycomb substrate having a first compartment and a second compartment The two compartments are open on the second outflow side end face and sealed on the second inflow side end face. The honeycomb filter is configured in series with the honeycomb structure relative to the flow of exhaust gas. The porosity of the partition wall of the first honeycomb substrate is 40% or more, and the opening ratio of the first inflow side end face of the first honeycomb substrate is 85% or more. A three-way catalyst is supported on the first honeycomb substrate and the second honeycomb substrate respectively. The honeycomb structure is disposed upstream of the honeycomb filter in the direction of exhaust gas flow. A radiant heat reduction mechanism is provided in at least one of the honeycomb structure, the honeycomb filter, and between the honeycomb structure and the honeycomb filter. The radiant heat reduction mechanism reduces the heat transfer caused by radiation from the honeycomb structure to the honeycomb filter.

[0014] [2] The second item of this utility model may also relate to the exhaust gas purification device described in the first item, characterized in that the honeycomb structure and the honeycomb filter are housed in a tank, and the radiant heat reduction mechanism is a low-radiation surface disposed on at least one of the first outflow side end face of the first honeycomb substrate and the second inflow side end face of the second honeycomb substrate, wherein the low-radiation surface has a lower emissivity than the first honeycomb substrate or the second honeycomb substrate in the state without the radiant heat reduction mechanism.

[0015] [3] The third item of this utility model may also relate to the waste gas purification device described in the second item, characterized in that the low radiation surface is composed of the surface of a layer of material with high reflectivity of mid-infrared electromagnetic waves with wavelength of 3 to 8 μm compared with at least one of the first inflow side end face and the second outflow side end face.

[0016] [4] The fourth item of this utility model may also relate to the waste gas purification device described in the second item, characterized in that the low radiation surface is formed by the surface of the oxygen defect induced surface heat treatment layer.

[0017] [5] The fifth item of this utility model may also relate to the waste gas purification device described in the second item, characterized in that the second inflow side end face has a sealing portion for sealing the second compartment, and the low radiation surface is composed of the surface of the sealing portion having an arithmetic mean roughness Ra of less than 10 μm.

[0018] [6] The sixth item of this utility model may also relate to the exhaust gas purification device described in the first item, characterized in that the radiant heat reduction mechanism is disposed on the second inflow side end face and is a catalyst that removes the soot adhering to the second inflow side end face by oxidation.

[0019] [7] The seventh item of this utility model may also relate to the exhaust gas purification device described in the first item, characterized in that the honeycomb structure and the honeycomb filter are housed in a tank, the radiant heat reduction mechanism is a heat insulation plate disposed between the honeycomb structure and the honeycomb filter, the heat insulation plate has multiple openings that allow exhaust gas to flow, and has a surface with a high reflectivity of mid-infrared electromagnetic waves with wavelengths of 3 to 8 μm compared with the first inflow side end face and the second outflow side end face of the first honeycomb substrate and the second honeycomb substrate.

[0020] [8] The eighth item of this utility model may also relate to the exhaust gas purification device described in the first item, characterized in that the honeycomb structure and the honeycomb filter are housed in a tank, and the radiant heat reduction mechanism is disposed between the honeycomb structure and the honeycomb filter, which is a space with a width of more than 30 mm in the direction of exhaust gas flow.

[0021] [9] The ninth item of this utility model may also relate to the exhaust gas purification device described in the eighth item, characterized in that an angle is provided between the central axis of the honeycomb structure and the central axis of the honeycomb filter.

[0022]

[10] The 10th item of this utility model may also relate to the exhaust gas purification device described in the 1st item, characterized in that the honeycomb structure is housed in the first tank, the honeycomb filter is housed in the second tank which is different from the first tank, and the radiant heat reduction mechanism is disposed between the first tank and the second tank and is a connecting pipe with a diameter smaller than that of the first tank and the second tank.

[0023]

[11] The 11th item of this utility model relates to an electric vehicle, which is an electric vehicle having an engine and a motor as a power source for driving, characterized in that it has an exhaust gas purification device provided in any one of the items 1 to 10 of the exhaust system of the engine.

[0024] Utility Model Effect

[0025] According to one embodiment of the exhaust gas purification device of the present invention and for use in electric vehicles, a radiative heat reduction mechanism is provided in at least one of the honeycomb structure, the honeycomb filter, and between the honeycomb structure and the honeycomb filter to reduce the heat transfer caused by radiation from the honeycomb structure to the honeycomb filter, thereby enabling the honeycomb structure to heat up earlier. Attached Figure Description

[0026] Figure 1 This is an explanatory diagram showing an electric vehicle according to an embodiment of the present invention.

[0027] Figure 2 yes Figure 1 A cross-sectional view of the exhaust gas purification device.

[0028] Figure 3 It means Figure 2 The front view of the first inflow side end face of the honeycomb structure.

[0029] Figure 4 It means Figure 2 A three-dimensional diagram of a honeycomb structure.

[0030] Figure 5 It means Figure 2 The front view of the second inflow side end face of the cellular filter.

[0031] Figure 6 It means Figure 2 A 3D view of a honeycomb filter.

[0032] Figure 7 It means Figure 2 A diagram illustrating the second method of the radiant heat reduction mechanism.

[0033] Figure 8 It means Figure 2 A third-party illustration of the radiant heat reduction mechanism.

[0034] Figure 9 It means Figure 8 Front view of the insulation panel.

[0035] Figure 10 It means Figure 2 A diagram illustrating the fourth method of the radiant heat reduction mechanism.

[0036] Figure 11 It means Figure 10 A graph showing the relationship between the width W of the space and the amount of heat transferred from the honeycomb structure to the honeycomb filter.

[0037] Figure 12 It means Figure 10 The diagram illustrates a variation of the radiant heat reduction mechanism.

[0038] Figure 13 It means Figure 2 A diagram illustrating the fifth method of the radiant heat reduction mechanism. Detailed Implementation

[0039] Hereinafter, embodiments for implementing this utility model will be described with reference to the accompanying drawings. This utility model is not limited to any particular embodiment, and can be embodied by modifying the constituent elements without departing from its spirit. Furthermore, various utility models can be formed by appropriately combining the multiple constituent elements disclosed in each embodiment. For example, several constituent elements may be deleted from all the constituent elements shown in the embodiments. Moreover, constituent elements from different embodiments may be appropriately combined.

[0040] <About Electrified Vehicles>

[0041] Figure 1 This is an explanatory diagram illustrating an embodiment of the electric vehicle 1 of this utility model. (See diagram for reference.) Figure 1 As shown, the electric vehicle 1 of this embodiment includes a motor 2, a battery 3, an engine 4 (internal combustion engine) and an exhaust gas purification device 5.

[0042] 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 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, storing the electricity generated by motor 2 in battery 3.

[0043] Engine 4 is used as a power source for driving and / or generating electricity. When engine 4 is used as a power source for driving, its output shaft is connected to wheel 1a, and the output of engine 4 drives wheel 1a, thus enabling the electrified vehicle 1 to move. When engine 4 is used as a power source for generating electricity, its output shaft is connected to a generator, and the output of engine 4 drives the generator. The generator can be motor 2, or it can be separate from motor 2. Engine 4 can be used solely as a power source for driving, or it can be used solely as a power source for generating electricity. When engine 4 is used solely as a power source for generating electricity, it is sometimes referred to as a range extender.

[0044] The electrified vehicle 1 is sometimes also referred to as a hybrid vehicle. Hybrid vehicles also include, for example, plug-in hybrid vehicles that can connect an external power source, such as a commercial power system, to the battery 3. In addition, the electrified vehicle 1 also includes range-extended electric vehicles (EVs) that use the engine 4 only as a power source for generating electricity, and extend the driving range by generating electricity through the engine 4 when the charging rate of the battery 3 decreases.

[0045] The exhaust gas purification device 5 is installed in the exhaust system 4a of the engine 4 to purify the exhaust gas 4b from the engine 4. The purification of exhaust gas 4b includes the purification of gaseous components such as NOx, HC and CO by a catalyst, and the removal of particulate matter generated by fuel combustion.

[0046] <About exhaust gas purification devices>

[0047] Next, Figure 2 yes Figure 1 A cross-sectional view of the exhaust gas purification device 5. Figure 3 It means Figure 2 The front view of the first inflow side end face 61 of the honeycomb structure 6. Figure 4 It means Figure 2 A three-dimensional view of the honeycomb structure 6. Figure 5 It means Figure 2 The front view of the second inflow side end face 71 of the cellular filter 7. Figure 6 It means Figure 2 A 3D view of the honeycomb filter 7.

[0048] like Figure 2 As shown, the exhaust gas purification device 5 has a honeycomb structure 6 and a honeycomb filter 7.

[0049] The honeycomb structure 6 has a first honeycomb substrate 60. The first honeycomb substrate 60 has porous partitions 64 that divide a plurality of compartments 63 extending from a first inflow side end face 61 to a first outflow side end face 62. The compartments 63 of the first honeycomb substrate 60 are open at both ends.

[0050] The honeycomb filter 7 has a second honeycomb substrate 70. The second honeycomb substrate 70 has porous partitions 74 that divide a plurality of compartments 73 extending from a second inflow side end face 71 to a second outflow side end face 72. The compartments 73 of the second honeycomb substrate 70 include: a first compartment 731 that is open at the second inflow side end face 71 and closed at the second outflow side end face 72, and a second compartment 732 that is open at the second outflow side end face 72 and closed at the second inflow side end face 71. The honeycomb filter 7 is configured in series with the honeycomb structure 6 in the flow of exhaust gas 4b.

[0051] The porosity of the partition walls 64 of the first honeycomb substrate 60 is 40% or more. A porosity of 40% or more reduces heat capacity and shortens heating time, thus suppressing increased pressure loss. Preferably, the porosity of the partition walls 64 is 55% or less. A porosity of 55% or less reduces the likelihood of the honeycomb structure 6 becoming brittle and easily detaching. The porosity is a value measured using a mercury porosity meter.

[0052] The opening ratio of the first inflow side end face 61 of the first honeycomb substrate 60 is 85% or more. With an opening ratio of 85% or more, the heat capacity at the end of the first inflow side end face 61 becomes excessively large, and the honeycomb structure 6 will not heat up sufficiently due to the heat of the exhaust gas 4b (the heating rate is slow), thus reducing the possibility of a decrease in the purification performance of the exhaust gas 4b. The opening ratio of the first inflow side end face 61 is preferably 92% or less. With an opening ratio of 92% or less, the possibility of the honeycomb structure 6 breaking when housed in the tank 90 due to insufficient strength can be reduced. The opening ratio is defined as the ratio of the area occupied by the void portion in the total area of ​​a plane perpendicular to the central axis. The opening ratio is measured by image analysis of the end face.

[0053] A three-way catalyst is supported on both the first honeycomb substrate 60 and the second honeycomb substrate 70. 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). Based on this three-way catalyst, hydrocarbons are purified into water and carbon dioxide through oxidation or reduction, carbon monoxide is purified into carbon dioxide through oxidation or reduction, and nitrogen oxides are purified into nitrogen through oxidation or reduction.

[0054] The honeycomb structure 6 is positioned upstream of the honeycomb filter 7 in the direction of the exhaust gas 4b flow.

[0055] A radiant heat reduction mechanism 8 is provided in at least one of the honeycomb structure 6, the honeycomb filter 7, and between the honeycomb structure 6 and the honeycomb filter 7. The radiant heat reduction mechanism 8 reduces the transfer of heat generated by radiation from the honeycomb structure 6 to the honeycomb filter 7.

[0056] In this electric vehicle 1, the engine 4 is started and stopped frequently, thus requiring high levels of early temperature rise during startup and high catalyst insulation during shutdown. When heat is transferred from the honeycomb structure 6 to the honeycomb filter 7 via radiation, the temperature rise of the honeycomb structure 6 slows down. If the temperature rise of the honeycomb structure 6 slows down, the purification performance of the catalyst in the honeycomb structure 6 for exhaust gas 4b during startup decreases. In the exhaust gas purification device 5 of this embodiment, a radiative heat reduction mechanism 8 is provided at least one of the honeycomb structure 6, the honeycomb filter 7, and between the honeycomb structure 6 and the honeycomb filter 7. This radiative heat reduction mechanism 8 reduces the heat transfer caused by radiation from the honeycomb structure 6 to the honeycomb filter 7, thus enabling the honeycomb structure 6 to heat up earlier. Therefore, the purification performance of the catalyst in the honeycomb structure 6 for exhaust gas 4b during startup can be improved.

[0057] Compared to the case where the radiant heat reduction mechanism 8 is not provided (where the same honeycomb structure 6 and honeycomb filter 7 made of the same material are mounted in the same configuration in the electric vehicle 1), the radiant heat reduction mechanism 8 reduces the heat transfer caused by radiation from the honeycomb structure 6 to the honeycomb filter 7. Whether or not the radiant heat reduction mechanism 8 is provided depends on whether the various methods of implementing the radiant heat reduction mechanism 8 and its specific examples described below in this specification are implemented. Furthermore, the various methods of implementing the radiant heat reduction mechanism 8 and its specific examples can be implemented individually or in combination.

[0058] <Regarding the first method of radiant heat reduction mechanisms>

[0059] like Figure 2 As shown, the honeycomb structure 6 and the honeycomb filter 7 can be housed in a tank 90. ​​The radiative heat reduction mechanism 8 can be a low-emissivity surface 80 disposed on at least one of the first outflow side end face 62 of the first honeycomb substrate 60 and the second inflow side end face 71 of the second honeycomb substrate 70. The low-emissivity surface 80 has a lower emissivity compared to the first honeycomb substrate 60 or the second honeycomb substrate 70 in the state where the radiative heat reduction mechanism 8 is not disposed.

[0060] When the emissivity of the first outflow side end face 62 of the first honeycomb substrate 60 is lower than that of the first honeycomb substrate 60 in the state without the radiative heat reduction mechanism 8, it is determined that a low-emissivity surface 80, serving as the radiative heat reduction mechanism 8, is provided on the first outflow side end face 62. Regarding the emissivity of the first outflow side end face 62, for a region cut from the axial center including this end face with a diameter of 1 cm... 2The cut test pieces with the above end-face areas were measured using JIS R 1693-2:2012 - Method for measuring emissivity of fine ceramics and ceramic composites (based on the method of measuring vertical emissivity using FTIR (Fourier Transform Infrared Spectrophotometer)). The emissivity of the first honeycomb substrate 60 without the radiative heat reduction mechanism 8 was set as the emissivity of the end face (the end face of the cordierite substrate) formed by cutting more than 1 mm from the surface of the first outflow side end face 62 of the first honeycomb substrate 60. The emissivity of this end face was also measured in the same way as the emissivity of the first outflow side end face 62.

[0061] Similarly, when the emissivity of the second inflow-side end face 71 of the second honeycomb substrate 70 is lower than the emissivity of the second honeycomb substrate 70 in the state where the radiative heat reduction mechanism 8 is not provided, it is determined that the low-emissivity surface 80, which serves as the radiative heat reduction mechanism 8, is provided on the second inflow-side end face 71. Regarding the emissivity of the second inflow-side end face 71 of the second honeycomb substrate 70, for a region cut from the axial center including this end face with a diameter of 1 cm... 2 The cut test pieces with the above end-face area were measured using JIS R1693-2:2012 - Method for measuring the emissivity of fine ceramics and ceramic composites (based on the method of measuring vertical emissivity using the reflection method with FTIR (Fourier Transform Infrared Spectrophotometer)). The emissivity of the second honeycomb substrate 70 without the radiative heat reduction mechanism 8 was set as the emissivity of the end face (the end face of the cordierite substrate) formed by cutting more than 1 mm from the surface of the second inflow side end face 71 of the second honeycomb substrate 70. The emissivity of this end face was also measured in the same way as the emissivity of the second inflow side end face 71. However, when the sealing portion surface of the second inflow side end face 71 of the second honeycomb substrate 70 is coated with an alumina catalyst, it can be determined that the above measurement is unnecessary and the radiative heat reduction mechanism 8 is applied to the second inflow side end face 71 of the second honeycomb substrate 70.

[0062] <First Approach Regarding Low-Radiation Surfaces>

[0063] The low-emissivity surface 80 can be formed by the surface of a layer of material with a high reflectivity for mid-infrared electromagnetic waves with wavelengths of 3 to 8 μm compared to at least one of the first inflow side end face 61 and the second outflow side end face 72. When the first honeycomb substrate 60 and the second honeycomb substrate 70 are made of cordierite, examples of materials constituting the layer of the low-emissivity surface 80 include cordierite material with introduced oxygen defects, alumina, cerium oxide, and zirconium oxide. The material constituting the low-emissivity surface 80 can be provided on at least one of the first outflow side end face 62 and the second inflow side end face 71 by introducing oxygen defects through heat treatment of the original substrate and coating with a low-emissivity material. The reflectivity is measured by the same measurement method as the emissivity described above. There exists a relationship where reflectivity + emissivity = 1. When the reflectivity of the material constituting the low-emissivity surface 80 is set as R1, and the reflectivity of the first honeycomb substrate 60 and the second honeycomb substrate 70 is set as R2, R1 can be more than 1.03 times, more than 1.05 times, or more than 1.1 times R2. When the second honeycomb substrate 70 (honeycomb filter 7) is coated with a catalyst, an alumina water coating containing precious metals, which serves as a catalyst, is also coated on the surface of the sealing portion of the second inflow side end face 71. This is particularly effective as a means of reducing the emissivity of the second inflow side end face 71.

[0064] <Regarding the second approach for low-radiation surfaces>

[0065] The low-emissivity surface 80 can be formed by the surface of an oxygen defect-induced surface heat-treated layer. An oxygen defect-induced surface heat-treated layer refers to a layer with numerous oxygen defects on its surface, generated by heat-treating the entire honeycomb substrate (first honeycomb substrate 60 and / or second honeycomb substrate 70) under a low-oxygen concentration atmosphere. The spectroscopic characteristics of the sample are measured using infrared light, and absorption peaks related to oxygen defects are determined based on analytical Fourier transform infrared spectroscopy (FTIR), thereby determining the presence or absence of oxygen defects. In the presence of oxygen defects, the low-emissivity surface 80 is identified as an oxygen defect-induced surface heat-treated layer.

[0066]

[0067] like Figure 5 As shown, the second inflow side end face 71 has a sealing portion 75 that seals the second compartment 732. The low-emissivity surface 80 may be formed by the surface of the sealing portion 75 having an arithmetic mean roughness Ra of 10 μm or less. The arithmetic mean roughness Ra is defined by JIS B0031:1994. The arithmetic mean roughness Ra is measured by a laser surface roughness meter.

[0068] <Regarding the second method of radiant heat reduction mechanism>

[0069] then, Figure 7 It means Figure 2A diagram illustrating a second embodiment of the radiative heat reduction mechanism 8 is provided. As described above, the radiative heat reduction mechanism 8 may be a catalyst 81 disposed on the second inflow side end face 71 and used to oxidize and remove soot adhering to the second inflow side end face 71. Soot has a higher emissivity (lower reflectivity) than cordierite substrate; therefore, if a large amount of soot adheres to the second inflow side end face 71, the heat transfer generated by radiation from the honeycomb structure 6 to the honeycomb filter 7 increases. By oxidizing and removing the soot using the catalyst 81, the heat transfer caused by radiation from the honeycomb structure 6 to the honeycomb filter 7 can be reduced. As such a catalyst 81, an oxidation-promoting catalyst can be used. Examples of such a catalyst 81 include alumina supported on platinum and palladium. Such a catalyst 81 also includes a ternary catalyst. The catalyst may be disposed on the second inflow side end face 71 as a water coating. Water coating refers to a coating made by impregnating or applying a slurry containing alumina as the main component, which is used as a catalyst carrier to support precious metal catalysts, onto the inner surface of the pores of the partition wall or the surface of the partition wall.

[0070] <On the Third Method of Radiant Heat Reduction Mechanism>

[0071] then, Figure 8 It means Figure 2 A third-party diagram illustrating the radiant heat reduction mechanism 8. Figure 9 It means Figure 8 The front view of the heat insulation plate 82. As described above, the honeycomb structure 6 and the honeycomb filter 7 can be housed in a tank 90. ​​The radiant heat reduction mechanism 8 can be the heat insulation plate 82 disposed between the honeycomb structure 6 and the honeycomb filter 7. Figure 9 As shown, the heat insulation plate 82 has multiple openings 820 that allow exhaust gas 4b to flow through. Furthermore, the heat insulation plate 82 has a surface with a reflectivity for mid-infrared electromagnetic waves (wavelength 3–8 μm) that is higher than that for the first inflow-side end face 61 and the second outflow-side end face 72 of the first honeycomb substrate 60 and the second honeycomb substrate 70. Stainless steel is an example of such a surface. The reflectivity of the surface of the heat insulation plate 82 for mid-infrared electromagnetic waves is measured according to JIS R 1801:2002. When the reflectivity of the surface of the heat insulation plate 82 is set as R3 and the reflectivity of the material of the honeycomb filter 7 is set as R4, R3 can be at least 1.03 times, at least 1.05 times, or at least 1.1 times that of R4.

[0072] The area of ​​the opening 820 can be more than 30% and less than 70% of the area of ​​the region surrounded by the outer edge of one side of the heat insulation plate 82. When the heat insulation plate 82 is circular, the area of ​​the region surrounded by the outer edge of one side of the heat insulation plate 82 is the area calculated based on the radius of the heat insulation plate 82 without considering the presence of the opening 820.

[0073] <Regarding the fourth method of radiant heat reduction mechanisms>

[0074] Next, Figure 10 It means Figure 2 A diagram illustrating the fourth method of the radiant heat reduction mechanism 8. Figure 11 It means Figure 10 A graph showing the relationship between the width W of the space 83 and the amount of heat transferred from the honeycomb structure 6 to the honeycomb filter 7. As described above, the honeycomb structure 6 and the honeycomb filter 7 can be housed in a tank 90. ​​The radiative heat reduction mechanism 8 can be a space 83 with a width W exceeding 30 mm in the direction of exhaust gas 4b, located between the honeycomb structure 6 and the honeycomb filter 7. Figure 11 As shown, the amount of heat transferred (W (J / sec)) generated by radiation from the honeycomb structure 6 to the honeycomb filter 7 is inversely proportional to the width W of the space 83. By making the width W exceed 30 mm, the amount of heat transfer can be suppressed to less than half compared to the case where the width W is 20 mm. From the viewpoint of suppressing the amount of heat transfer, there is no particular upper limit to the width W of the space 83. However, from the viewpoint of the compatibility with the exhaust aftertreatment system, an upper limit of 200 mm can be listed as the width W of the space 83.

[0075] then, Figure 12 It means Figure 10 A diagram illustrating a variation of the radiant heat reduction mechanism 8. (See diagram for example.) Figure 12 As shown, an angle θ can be set between the central axis CA1 of the honeycomb structure 6 and the central axis CA2 of the honeycomb filter 7. By setting the angle θ, the radiation density of the heated surface can be reduced. Furthermore, when such an angle θ is set, the width W of the space 83 is defined as the narrowest width (the width of the curved inner side) between the honeycomb structure 6 and the honeycomb filter 7 in the direction of exhaust gas 4b flow. The direction of exhaust gas 4b flow is the direction in which the inner surface of the tank 90 extends.

[0076] Figure 12The diagram shows the arrangement of the central axis CA1 of the honeycomb structure 6 and the central axis CA2 of the honeycomb filter 7 when viewed in a cross-section extending orthogonally to the directions of the compartments 63 and 73 of the honeycomb structure 6 and the honeycomb filter 7. In this case, the angle θ is defined as the smaller of the angles formed by the central axes CA1 and CA2 in this cross-section. When the respective central axes CA1 and CA2 do not intersect in this cross-section, the angle θ is defined as the smallest angle formed by the vector extending along the central axis CA1 of the honeycomb structure 6 and the vector extending along the central axis CA2 of the honeycomb filter 7. From the viewpoint of reducing heat transfer caused by radiation, the angle θ is preferably 10° or more, more preferably 20° or more. Furthermore, from the viewpoint of reducing flow pressure loss, the angle θ is preferably 60° or less, more preferably 45° or less.

[0077] <Fifth Method Regarding Radiant Heat Reduction Mechanisms>

[0078] then, Figure 13 It means Figure 2 A diagram illustrating the fifth method of the radiant heat reduction mechanism 8. (See diagram for reference.) Figure 13 As shown, the honeycomb structure 6 can be housed in the first tank 91, and the honeycomb filter 7 can be housed in a second tank 92, which is different from the first tank 91. The radiant heat reduction mechanism 8 can be a connecting pipe 84 disposed between the first tank 91 and the second tank 92, with a diameter smaller than that of both the first tank 91 and the second tank 92. By connecting the first tank 91 and the second tank 92 using the small-diameter connecting pipe 84, direct radiation can be blocked. Figure 13 In this design, a connecting pipe 84 is embedded on the outer side of the ends of the first tank 91 and the second tank 92. However, the connecting pipe 84 may also be embedded on the inner side of the ends of the first tank 91 and the second tank 92.

[0079] The diameters of the first tank 91, the second tank 92, and the connecting pipe 84 are defined as their respective inner diameters. Specifically, the diameter of the first tank 91 is defined as the inner diameter of the first tank 91 at the center of the honeycomb structure 6 in the direction of exhaust gas 4b, and the diameter of the second tank 92 is defined as the inner diameter of the second tank 92 at the center of the honeycomb filter 7 in the direction of exhaust gas 4b. When the inner diameter of the connecting pipe 84 varies in the direction of exhaust gas 4b, the diameter of the connecting pipe 84 is defined as the largest inner diameter.

[0080] exist Figure 13The diagram shows the connecting pipe 84 as separate from the first tank 91 and the second tank 92, but the connecting pipe 84 can also be integrally formed with the first tank 91 and the second tank 92. Regardless of whether the connecting pipe 84 is separate from the first tank 91 and the second tank 92 or integrally formed, the portion of the first tank 91 and the second tank 92 that is less than 0.6 times the diameter of the second tank 92 is used as the connecting pipe 84.

[0081] When the diameter of the connecting pipe 84 is set to D1, and the smaller of the diameters of the first tank 91 and the second tank 92 is set to D2, D1 can be less than 0.6 times, less than 0.5 times, or less than 0.4 times D2. The length of the connecting pipe 84 in the flow direction of the exhaust gas 4b can be more than 10 mm and less than 700 mm. The length of the connecting pipe 84 is defined as a local length having a diameter less than 0.6 times D2. The connecting pipe 84 can be as follows: Figure 13 The method shown is for straight pipes, but it can also be for curved pipes.

[0082] The following provides a more detailed description of the honeycomb structure 6 and the honeycomb filter 7.

[0083] <About honeycomb structures>

[0084] like Figure 2As shown, in the honeycomb structure 6, the first honeycomb substrate 60 has a honeycomb shape with porous partitions 64, which divide the honeycomb structure 6 into multiple compartments 63 that extend from the first inflow side end face 61 to the first outflow side end face 62, forming a flow path for the fluid. The compartments 63 formed in the honeycomb structure 6 ensure the flow path of the fluid from the first inflow side end face 61 to the first outflow side end face 62 (the compartments 63 are not sealed). Therefore, even if a large amount of three-way catalyst is loaded in the partitions 64 of the honeycomb structure 6, it is difficult to impede the flow of the fluid (exhaust gas 4b), and the increase in pressure loss is small. Therefore, it is possible to increase the loading of the three-way catalyst per unit volume. It should be noted that in the honeycomb structure 6, 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 on the first inflow side end face 61 side is greater than the loading of the three-way catalyst at other parts. On the other hand, if the loading per unit volume of the three-way catalyst on the end of the first inflow side face 61 is less than the loading per unit volume of the three-way catalyst on other parts, the heat generated by the catalytic reaction at the end of the fluid inflow side (the end of the first inflow side face 61) is insufficient, thus the heating rate decreases. Therefore, time is spent before reaching the catalyst's active temperature, and the purification performance of exhaust gas 4b may become insufficient. If the loading per unit volume of the three-way catalyst is greater than the loading per unit volume of the three-way catalyst on other parts, the heat generated by the catalytic reaction at the end of the first inflow side face 61 is increased compared to other parts, thus enabling a larger amount of the three-way catalyst to reach the catalyst active temperature earlier after engine start-up. Figure 3 It is a schematic representation Figure 2 The diagram shows a top view of the first inflow side end face 61 of the honeycomb structure 6. The end of the first inflow side end face 61 is located in the range from the first inflow side end face 61 to a position that is 10% to 60% of the length of the honeycomb structure 6 along its central axis.

[0085] The shape of the honeycomb structure 6 is not limited to Figure 4 The cylindrical shape shown can be exemplified by elliptical cylindrical shapes, quadrangular cylindrical shapes, and cylindrical shapes with polygonal bases, as well as cylindrical shapes with irregular bases.

[0086] Specifically, the size of the honeycomb structure 6 is preferably 30 to 200 mm in length along the central axis.

[0087] The diameter of the honeycomb structure 6 can be the same as or smaller than the diameter of the honeycomb filter 7. Preferably, the diameter of the honeycomb structure 6 is smaller than the diameter of the honeycomb filter 7. When the diameter of the honeycomb structure 6 is smaller than the diameter of the honeycomb filter 7, the honeycomb structure 6 becomes lighter than the honeycomb filter 7, provided that the length of the honeycomb structure 6 along its central axis is the same as or shorter than the length of the honeycomb structure 6 along its central axis. Therefore, the heating rate is faster, and the honeycomb structure 6 can easily reach the catalyst activation temperature in the early stages after engine start-up. Here, since there is a limit to increasing the volume of the canister 90, reducing the size of the honeycomb structure 6 allows for a larger honeycomb filter 7. Moreover, if the honeycomb filter 7 is larger, it can efficiently remove particulate matter from the exhaust gas 4b.

[0088] When the diameter of the honeycomb structure 6 is smaller than the diameter of the honeycomb filter 7, the diameter of the honeycomb structure 6 is preferably 50% to 80% of the diameter of the honeycomb filter 7, more preferably 55% to 75%, and even more preferably 60% to 70%. By setting the diameter within the above range, the honeycomb structure 6 can be heated at a better rate using 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%, the honeycomb structure 6 may not heat up sufficiently due to the heat of the exhaust gas 4b (the heating rate becomes slower). Furthermore, for example, when the honeycomb structure 6 is cylindrical, the diameter of its bottom surface is preferably 80 mm to 180 mm. When the shape of the honeycomb structure 6 is other than 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.

[0089] The thickness of the partition wall 64 is preferably 50.8–101.6 μm, more preferably 50.8–75 μm, and particularly preferably 65–75 μm. If it is less than 50.8 μm, the strength of the honeycomb structure 6 may decrease. On the other hand, if it exceeds 101.6 μm, the pressure loss when the exhaust gas 4b passes through the compartment 63 may increase. The thickness of the partition wall 64 is determined by microscopic observation of a cross-section parallel to the central axis.

[0090] The cell density of the first honeycomb substrate 60 (i.e., the cell density of the cross section orthogonal to the central axis of the first honeycomb substrate 60 (honeycomb structure 6)) can be greater than that of the second honeycomb substrate 70. Furthermore, the aperture ratio of the first inflow side end face 61 of the honeycomb structure 6 can be greater than that of the second inflow side end face 71 of the honeycomb filter 7. With such a higher cell density and aperture ratio, the partition walls 64 of the honeycomb structure 6 are thinner than the partition walls 74 of the honeycomb filter 7. Therefore, when the honeycomb structure 6 and the honeycomb filter 7 have the same volume, or when the volume of the honeycomb structure 6 is smaller than that of the honeycomb filter 7, the honeycomb structure 6 is lighter than the honeycomb filter 7. Consequently, in the early stages after engine startup, the honeycomb structure 6 more easily reaches the catalyst activation temperature.

[0091] Specifically, the cell density of the first honeycomb substrate 60 is preferably 32 to 186 cells / cm². 2 More preferably, 40–100 per cm 2 The preferred size is 50-60 per cm. 2 If within the above range, the contact area between exhaust gas 4b and honeycomb structure 6 increases, and in the early stages after engine start-up, honeycomb structure 6 easily reaches the catalyst activation temperature. If it is less than 32 cells / cm²... 2 If this occurs, the strength of the honeycomb structure 6 may decrease. On the other hand, if it exceeds 186 cells / cm²... 2 If this happens, the pressure loss may increase.

[0092] The opening ratio of the first inflow side end face 61 of the honeycomb structure 6 can be greater than that of the second inflow side end face 71 of the honeycomb filter 7. However, in this case, it is preferable that the porosity of the partition wall 64 of the first honeycomb substrate 60 is less than that of the partition wall 74 of the second honeycomb substrate 70. If the porosity of the partition wall 64 is less than that of the partition wall 74, the strength of the honeycomb structure 6 can be ensured. That is, when the opening ratio of the first inflow side end face 61 of the honeycomb structure 6 is greater than that of the second inflow side end face 71 of the honeycomb filter 7, the heat capacity of the honeycomb structure 6 is smaller than that of the honeycomb filter 7, and therefore the honeycomb structure 6 heats up faster than the honeycomb filter 7. However, the strength of the honeycomb structure 6 may become insufficient. Therefore, the porosity of the partition wall 64 is preferably less than that of the partition wall 74. Furthermore, since the honeycomb structure 6 heats up in the early stage, the heat from the exhaust gas 4b can be used to heat up the honeycomb structure 6. That is, the honeycomb filter 7 can be heated up rapidly.

[0093] The ratio of the length of the first honeycomb substrate 60 along its central axis to the diameter of the first inflow side end face 61 is preferably 0.1 to 0.4, more preferably 0.15 to 0.35, and particularly preferably 0.2 to 0.3. If it is less than 0.1, the residence time of the exhaust gas 4b in the first honeycomb substrate 60 (honeycomb structure 6) becomes shorter, and therefore the honeycomb structure 6 cannot be sufficiently heated by the heat of the exhaust gas 4b, which may prevent it from fully obtaining the purification performance immediately after the engine starts. On the other hand, if it exceeds 0.4, the honeycomb structure 6 becomes too heavy (the density becomes too high), and therefore cannot be sufficiently heated by the heat of the exhaust gas 4b, which may prevent it from fully obtaining the purification performance of the exhaust gas 4b.

[0094] The average pore size of the partition wall 64 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 64 cannot be achieved when forming a catalyst layer by supporting the ternary catalyst on the partition wall 64, and the catalyst layer may peel off. On the other hand, if it exceeds 30 μm, the honeycomb structure 6 may become brittle and easily detach. The average pore size of the partition wall 64 is a value measured with a mercury porosity meter.

[0095] The shape of the compartment 63 of the first honeycomb substrate 60 is not particularly limited. In a cross-section orthogonal to the central axis, it is preferably a polygon such as a triangle, quadrilateral, pentagon, hexagon, or octagon, or a circle or ellipse, or other irregular shapes. A combination of quadrilaterals and octagons is also a preferred option.

[0096] Furthermore, the hydraulic diameters of all the compartments in the first honeycomb substrate 60 can be the same, and the hydraulic diameters of the compartment 63 opening at the first inflow side end face 61 and the compartment 63 opening at the first outflow side end face 62 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, in order to reduce pressure loss, it is preferable that the hydraulic diameter of the compartment 63 opening at the first outflow side end face 62 is larger than the hydraulic diameter of the compartment 63 opening at the first inflow side end face 61, and preferably that the hydraulic diameter of the compartment 63 opening at the first inflow side end face 61 is 20% to 45% of the hydraulic diameter of the compartment 63 opening at the first outflow side end face 62. In this specification, the "hydraulic diameter of the compartment" is a value calculated using the formula "4 × (cross-sectional area) / (perimeter)". Here, "cross-sectional area" refers to the area of ​​the compartment in a section orthogonal to the direction in which the compartment extends, and "perimeter" refers to the "length of the outer perimeter of the compartment" in a section orthogonal to the direction in which the compartment extends.

[0097] The first honeycomb substrate 60 (spacer 64) is primarily composed of ceramic. Specifically, the material of the spacer 64 is preferably selected from at least one group selected from 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, "primarily composed of ceramic" means that the entire substrate contains at least 90% ceramic by mass.

[0098] Furthermore, the honeycomb structure 6 may 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 structure 6. 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.

[0099] The loading of the three-way catalyst per unit volume supported on the honeycomb structure 6 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 startup. If it exceeds 400 g / L, the loading per unit volume is too large, narrowing the flow path of the compartment 63 with openings at both ends, which may increase pressure loss.

[0100] <About Cellular Filters>

[0101] like Figure 2 As shown, in the honeycomb filter 7, the second honeycomb substrate 70 has a honeycomb shape with porous partitions 74, which divides into a plurality of compartments 73 that form a flow path for fluid from the second inflow side end face 71 to the second outflow side end face 72. Figure 5 This is a schematic top view showing the second inflow side end face 71 of the honeycomb filter 7. The shape of the honeycomb filter 7 is not limited to... Figure 6 The cylindrical shape shown can be exemplified by elliptical cylindrical shapes, quadrangular cylindrical shapes, and cylindrical shapes with polygonal bases, as well as cylindrical shapes with irregular bases.

[0102] Furthermore, the size of the honeycomb filter 7 is preferably such that its length along the central axis is 50 to 200 mm. Additionally, for example, when the honeycomb filter 7 is cylindrical, its bottom diameter is preferably 80 to 180 mm. When the honeycomb filter 7 is not cylindrical, its bottom area is preferably within the same range as the bottom area in the cylindrical case described above.

[0103] The thickness of the partition wall 74 is preferably 127–508 μm, more preferably 200–400 μm, and particularly preferably 250–350 μm. If it is less than 127 μm, the strength of the honeycomb filter 7 may decrease. On the other hand, if it exceeds 508 μm, the pressure loss when the exhaust gas 4b passes through the compartment 73 may increase. The thickness of the partition wall 74 is determined by microscopic observation of a cross-section parallel to the central axis.

[0104] The cell density of the second honeycomb substrate 70 (honeycomb filter 7) (i.e., the cell density of the cross section orthogonal to the central axis of the second honeycomb substrate 70) is preferably 7.7 to 46.5 cells / cm². 2 More preferably, 10–40 per cm 2 The preferred density is 15-25 per cm. 2 If less than 7.7 / cm 2 If the strength of the honeycomb filter 7 is reduced, then the strength of the filter may decrease. On the other hand, if it exceeds 46.5 cells / cm²... 2 If this happens, the pressure loss may increase.

[0105] The porosity of the partition wall 74 of the second honeycomb substrate 70 is preferably 35% to 80%, more preferably 38% to 65%, and particularly preferably 45% to 65%. If it is less than 35%, the pressure loss may increase. On the other hand, when it exceeds 80%, the honeycomb filter 7 may sometimes become brittle and easily fall off. The porosity of the partition wall 74 is a value measured by a mercury porosity meter.

[0106] The ratio of the length of the second honeycomb substrate 70 along its central axis to the diameter of the second inflow side end face 71 is preferably 0.5 to 1.5, more preferably 0.8 to 1.5, and particularly preferably 1.1 to 1.3. If it is less than 0.5, the length of the second honeycomb substrate 70 along its central axis becomes too short, thus reducing the filtration area and deteriorating the collection efficiency; furthermore, the pressure loss may increase. On the other hand, if it exceeds 1.5, the length of the second honeycomb substrate 70 along its central axis becomes too long, thus increasing the pressure loss within the compartment flow path; therefore, the overall pressure loss of the honeycomb filter 7 may become excessive.

[0107] The average pore size of the partition wall 74 is preferably 7 μm to 40 μm, more preferably 8 μm 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, if it exceeds 40 μm, the honeycomb filter 7 may become brittle and easily detach, or the collection performance of particulate matter may decrease. The average pore size of the partition wall 74 is a value measured by a mercury porosity meter.

[0108] The shape of the compartments 73 in the second honeycomb substrate 70 is not particularly limited. In a cross-section orthogonal to the central axis, it is preferably a polygon, circle, or ellipse, such as a triangle, quadrilateral, pentagon, hexagon, or octagon, or other irregular shape. A combination of quadrilaterals and octagons is also preferred. Furthermore, it is preferable that in a cross-section orthogonal to the direction in which the compartments 73 extend, all compartments 73 have the same cross-sectional area, but the cross-sectional area of ​​the second compartment 732 with the sealing portion 75 on the second inflow side end face 71 (the cross-sectional area in the cross-section orthogonal to the direction in which the compartments 73 extend) is smaller than the cross-sectional area of ​​the first compartment 731 with the sealing portion 75 on the second outflow side end face 72 (the cross-sectional area in the cross-section orthogonal to the direction in which the compartments 73 extend). If this is the case, the increase in pressure loss when capturing particulate matter in the exhaust gas 4b can be suppressed.

[0109] Furthermore, the hydraulic diameters of all compartments in the second honeycomb substrate 70 can be identical, and the hydraulic diameters of the first compartment 731 and the second compartment 732 can also be different, but it is preferable that the hydraulic diameters are different. Specifically, in the case of purifying the exhaust gas 4b of a gasoline engine, in order to reduce pressure loss, it is preferable that the hydraulic diameter of the second compartment 732 is larger than that of the first compartment 731, and the hydraulic diameter of the first compartment 731 is preferably 20% to 45% of the hydraulic diameter of the second compartment 732.

[0110] The second honeycomb substrate 70 (spacer 74) is primarily composed of ceramic. Specifically, the material of the spacer 74 is preferably selected from at least one group selected from 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, "primarily composed of ceramic" means that the entire substrate contains at least 90% ceramic by mass.

[0111] Furthermore, the honeycomb filter 7 may 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 the outer peripheral wall formed 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 7. 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.

[0112] The catalyst loading per unit volume in the honeycomb filter 7 can be less than the three-way catalyst loading per unit volume in the partitions 64 of the honeycomb structure 6. By adjusting the catalyst loading per unit volume in this way, the heat generated by the catalytic reaction can be increased. That is, even with 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 7 and the honeycomb structure 6. However, when the ratio of the three-way catalyst loaded in the partitions 64 of the honeycomb structure 6 is increased, the heat generated by the catalytic reaction increases, and therefore the heating rate of the honeycomb structure 6 increases. Therefore, in the early stage after engine start-up, that is, in the short time after the engine just starts running, the catalyst (including the three-way catalyst) easily reaches the activation temperature. Furthermore, the heat from the exhaust gas 4b heated by the honeycomb structure 6 can also be used to heat the honeycomb structure 6.

[0113] Specifically, the catalyst loading per unit volume in the honeycomb filter 7 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 74 will be blocked by the catalyst, and the pressure loss may become too large.

[0114] The sealing portion 75 disposed in the honeycomb filter 7 can be made of a sealing material comprising ceramic raw material, water or alcohol, and organic binder. Preferably, the ceramic raw material is the same as that used as the raw material for the second honeycomb substrate 70 (the partition wall 74 of the second honeycomb substrate 70). Thus, during firing, the sealing portion 75 is firmly bonded to the partition wall 74.

[0115] The sealing section 75 is preferably configured to alternately seal the first compartment 731 and the second compartment 732, and the two end faces are in a checkered pattern.

[0116] The depth of the sealing portion 75 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 75 may be reduced. On the other hand, if it is deeper than 5 mm, the PM capture area of ​​the partition wall 74 may be smaller. Here, the depth of the sealing portion 75 refers to the length of the sealing portion 75 in the direction extending from the compartment 73.

[0117] The canister 90 is not particularly limited and can be any canister commonly used for purifying ceramic honeycomb filters, such as those used for automobile exhaust. Examples of materials for the canister 90 include ferritic stainless steel. The size of the canister 90 is preferably such that it can be pressed in while the cushioning material 95 is wound around the honeycomb structure 6 and the honeycomb filter 7. A canister with a length of approximately 100 to 300 mm is preferred for the canister 90.

[0118] As a method for arranging the cellular structure 6 and the cellular filter 7 separately at intervals, for example, one could be to arrange... Figure 2 The method shown describes the arrangement of the partition plates 96 and the like between them. For example, stainless steel or other metals can be used as the material for the partition plates 96.

[0119] in addition, Figure 2 In the exhaust gas purification device 5 shown, the honeycomb structure 6 and the honeycomb filter 7 are respectively disposed inside the tank 90 with their outer peripheries covered by a cushioning material 95. This cushioning material 95 prevents damage to the honeycomb structure 6 and the honeycomb filter 7. Furthermore, the honeycomb structure 6 and the honeycomb filter 7 are preferably housed inside the tank 90 under pressure applied from the outside via the cushioning material 95. This placement prevents the honeycomb structure 6 and the honeycomb filter 7 from moving within the tank 90, ensuring their stability within the tank 90. ​​The cushioning material 95 can be a ceramic fiber liner or the like.

[0120] <Manufacturing Method of Waste Gas Purification Device>

[0121] 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.

[0122] The manufacturing method includes: a honeycomb structure forming step, in which a catalyst slurry containing a ternary catalyst flows from a first inflow side end face of a first honeycomb substrate into multiple compartments, and the catalyst slurry (supporting the ternary catalyst) is coated on the wall surface of the multiple compartments to form a honeycomb structure, wherein the first honeycomb substrate is obtained by firing a first honeycomb molded body having porous walls dividing to form multiple compartments, the multiple compartments extending from the first inflow side end face to the first outflow side end face and forming a flow path for the fluid; and a honeycomb filter forming step, in which a honeycomb filter is formed by dividing the honeycomb structure into a honeycomb structure. After sealing the openings of predetermined compartments on one end face and the openings of remaining compartments on the other end face of a second honeycomb molded body with porous partition walls forming multiple compartments, a honeycomb filter with sealed openings is formed by firing. This filter is then formed on a second honeycomb substrate and the second inflow-side end face of the second honeycomb substrate, where the openings of predetermined compartments and the openings of remaining compartments on the second outflow-side end face are fitted with sealed openings. The multiple compartments extend from the second inflow-side end face to the second outflow-side end face, forming a flow path for fluid. An assembly process is also performed, which includes an inlet for waste gas inflow and... A honeycomb structure is arranged on the inlet side of the tank at the outlet of the purified waste gas outlet, with the first inlet side end face facing the inlet side of the tank. A honeycomb filter is arranged on the outlet side of the tank with the second outlet side end face facing the outlet side of the tank, thereby housing the honeycomb structure and the honeycomb filter within the tank. The honeycomb structure formed in the honeycomb structure forming process has a length in the central axis direction of the honeycomb structure relative to the length in the central axis direction of the honeycomb filter of 0.1 to 0.5. The cell density of the first honeycomb substrate constituting the honeycomb structure is greater than the cell density of the second honeycomb substrate constituting the honeycomb filter. The opening ratio of the first inlet side end face of the honeycomb structure is greater than the opening ratio of the second inlet side end face of the honeycomb filter. The diameter of the honeycomb structure is the same as or smaller than the diameter of the honeycomb filter. The honeycomb filter formed in the honeycomb filter forming process preferably does not support a catalyst, or it 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. The above-described process enables the manufacture of the waste gas purification device of this utility model.

[0123] <About the honeycomb structure formation process>

[0124] The first 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 shaped into a honeycomb shape to obtain a first honeycomb molded body. Next, the obtained first honeycomb molded body is fired to obtain the first honeycomb substrate.

[0125] The preferred forming 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.

[0126] As a ceramic raw material, it is preferably selected from at least one group consisting of 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 forming raw material is preferably 80-95% by mass.

[0127] Examples of organic binders include methylcellulose, hydroxypropoxycellulose, hydroxyethylcellulose, carboxymethylcellulose, and polyvinyl alcohol. Methylcellulose and hydroxypropoxycellulose are preferred in combination. The binder content relative to the total molding material is preferably 1-10% by mass. They can be used alone or in combination of two or more.

[0128] 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. It can be used alone or in combination with two or more materials.

[0129] Surfactants such as ethylene glycol, dextrin, fatty acid soaps, and polyols can be used. They can be used alone or in combination of two or more. The surfactant content relative to the total molding raw material is preferably 0.1% to 5% by mass.

[0130] The content of the dispersion medium is preferably 0.1 to 5% by mass relative to the total amount of the forming raw material.

[0131] 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.

[0132] There are no particular limitations on the method for 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 compartment shape, compartment thickness, and compartment density. As for the die material, a wear-resistant, ultra-hard alloy is preferred.

[0133] The firing temperature can be appropriately determined according to the material of the first honeycomb molded body. For example, when the material of the first honeycomb molded body is cordierite, the firing temperature is preferably 1380 to 1450°C, and more preferably 1400 to 1440°C. In addition, the firing time is preferably set to 3 to 10 hours.

[0134] Alternatively, the first honeycomb molded body can 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, the drying conditions are preferably set at a drying temperature of 30–150°C and a drying time of 1 minute to 2 hours.

[0135] Next, the method for coating the catalyst slurry (supported 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 compartment by impregnation and attraction. Preferably, the catalyst slurry is coated on the entire surface of the partition wall within the compartment. Then, after the catalyst slurry has poured into the compartment, any remaining slurry is blown away with compressed air. Then, by drying and baking the catalyst slurry, a honeycomb structure with the three-way catalyst supported on the surface of the partition wall within the compartment can be obtained. The drying conditions are preferably set to 80–150°C for 1–6 hours. Alternatively, the baking conditions are preferably 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.

[0136] <About the honeycomb filter forming process>

[0137] The second honeycomb molded body used in the honeycomb filter forming process can be made as follows: The clay is extruded into a honeycomb shape in a manner that meets the following conditions to obtain the second honeycomb molded body.

[0138] In this extrusion molding process, the blank extruded from the die is cut 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, the die is used such that the cell density of the first honeycomb substrate of the honeycomb structure is greater than the cell density of the second honeycomb substrate of the honeycomb filter, the opening ratio of the first inflow side end face of the honeycomb structure is greater than the opening ratio of the second inflow side end face of the honeycomb filter, and furthermore, the diameter of the honeycomb structure is the same as or smaller than the diameter of the honeycomb filter.

[0139] One method for sealing the openings of the compartments in the second honeycomb molded body is to fill the openings with a sealing material. Specifically, as a method of filling the sealing material, a mask is applied to one end face of the second honeycomb molded body to block the openings of predetermined compartments. Here, there are no particular limitations on the method of applying the mask, but it is preferable to alternately seal the openings of predetermined compartments in the second outflow side end face and the openings of remaining compartments in the second inflow side end face of the second honeycomb substrate, and to apply the mask in a checkered pattern on both end faces. Then, a slurry-like sealing material comprising a ceramic raw material, water or alcohol, and an organic binder is stored in a storage container. As the ceramic raw material, it is preferable to use the same ceramic raw material as the raw material for the second honeycomb molded body. The ceramic raw material is preferably 70-90% by mass of the total sealing material. Additionally, 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 hydroxypropoxymethylcellulose and methylcellulose. Then, the end with the mask applied is immersed in a storage container, and a sealing material is filled into the opening of the unmasked compartment to form a sealing portion. The viscosity of the sealing material is preferably 600 to 1200 Pa·s. Furthermore, the viscosity of the sealing material is measured at 30°C using a rotational viscometer at a rotational speed of 30 rpm.

[0140] Then, a mask is applied to the other end face of the second honeycomb molded body to block the openings of the remaining compartments. Next, 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 compartments to form sealing portions. In this way, a honeycomb filter molded body can be obtained in which the openings of predetermined compartments on one end face of the second honeycomb molded body and the openings of the remaining compartments on the other end face are equipped with sealing portions.

[0141] The firing temperature during the firing of 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 to 1450°C, and more preferably 1400 to 1440°C. In addition, the firing time is preferably set to about 3 to 10 hours.

[0142] Alternatively, the honeycomb filter molded body can 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, the drying conditions are preferably set at a drying temperature of 30°C to 150°C and a drying time of 1 minute to 2 hours.

[0143] It should be noted that, before the second honeycomb molding body forms the sealing portion, the second honeycomb molding body can be fired to obtain a honeycomb fired body. The opening of the predetermined compartment in one end face and the opening of the remaining compartment in the other end face of the obtained honeycomb fired body are formed into sealing portions, and then further fired to obtain a honeycomb filter.

[0144] It should be noted that a honeycomb filter can be obtained by coating a honeycomb filter structure with a catalyst slurry (supported catalyst) 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 impregnated and drawn into the compartment. Preferably, the catalyst slurry is coated on the entire surface of the partition wall within the compartment. After the catalyst slurry has flowed into the compartment, any remaining slurry is blown away with compressed air. Then, by drying and baking the catalyst slurry, a sealed honeycomb structure with the catalyst supported on the partition wall surface within the compartment can be obtained. The drying conditions are preferably set to 80–150°C for 1–6 hours. The baking conditions are preferably 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.

[0145] <About the assembly process>

[0146] In the assembly process, after covering the outer periphery of the honeycomb structure and the honeycomb filter with cushioning material, the honeycomb structure and the honeycomb filter, covered with cushioning material, are placed inside the tank. At this point, it is preferable that the honeycomb structure and the honeycomb filter are housed in a compressed state within the tank. Ceramic fiber gaskets, for example, can be used as cushioning material. This prevents the honeycomb structure and the honeycomb filter from moving within the tank.

[0147] The tank body can use conventionally known tank bodies, for example, it can be manufactured by stamping and welding sheet material made of ferritic 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.

[0148] 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 ordinary knowledge in the technical field to which the present invention pertains can conceive of various modifications or alterations within the scope of the technical concept described in the claims, and these are naturally understood to fall within the technical scope of the present invention.

[0149] [Example]

[0150] The present invention will be described in more detail below through embodiments. The present invention is not limited to these embodiments.

[0151] (Example 1)

[0152] [Fabrication of Honeycomb Structures] (Honeycomb Structure Formation Process)

[0153] First, as raw materials for cordierite petrochemicals, alumina, aluminum hydroxide, kaolin, talc, and silica are used. 35 parts by weight of dispersion medium, 6 parts by weight of organic binder, and 0.5 parts by weight of dispersant are added to 100 parts by weight of the cordierite petrochemical raw materials, respectively, and then mixed and kneaded to prepare clay. Water is used as the dispersion medium, hydroxypropyl methylcellulose as the organic binder, and ethylene glycol as the dispersant.

[0154] Next, the clay is extruded using a predetermined mold to form a honeycomb molded body with quadrilateral compartments and an overall cylindrical shape. Then, the honeycomb molded body is dried using a microwave dryer, and further dried completely using a hot air dryer. Afterward, both ends of the honeycomb molded body are cut off and adjusted to predetermined dimensions. Finally, the honeycomb molded body is fired at 1410–1440°C for 5 hours to obtain a fired honeycomb body.

[0155] Next, a mixture of γAl₂O₃ with an average particle size of 100 μm and CeO₂ with an average particle size of 100 μm (specific surface area 50 m²) was prepared. 2 / g) Wet crushing was performed using a ball mill to obtain crushed particles with an average particle size of 5 μm. The obtained crushed particles were impregnated in a solution containing Pt and Rh, so that Pt and Rh were supported in the pores of the crushed particles. Then, acetic acid and water were added to the crushed particles supported with Pt and Rh to obtain a coating slurry. The inflow-side end of the prepared honeycomb sintered body was impregnated with the obtained coating slurry. Then, with the inflow-side end impregnated, the coating slurry was vacuumed from the outflow-side end face of the honeycomb sintered body, thereby coating the slurry on the partition wall of the honeycomb sintered body to form a catalyst layer. Then, it was dried and fired at 600°C for 3 hours to produce a honeycomb structure.

[0156] The fabricated honeycomb structure has a diameter of 118 mm, a length along its central axis of 90 mm, and a cell density of 400 cpsi (62.0 cells / cm²). 2 The porosity of the partition wall is 55.0%, the compartment opening rate is 88%, and the catalyst loading is 200 g / L.

[0157] It should be noted that the catalyst supported on the honeycomb structure has a loading of 1 g / L per unit volume for oxides (γAl2O3 and CeO2) in the Pt honeycomb catalyst body, and a loading of 0.2 g / L per unit volume in the Rh honeycomb catalyst body. Furthermore, the average pore size of the catalyst layer is the same as the average particle size of the broken particles, which is 5 μm.

[0158] [Creation of a Honeycomb Filter] (Honeycomb Filter Formation Process)

[0159] First, as a cordierite petrochemical raw material, alumina, aluminum hydroxide, kaolin, talc, and silica are used. To each 100 parts by weight of the cordierite petrochemical raw material, 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, followed by mixing and kneading to prepare a blank. 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.

[0160] Next, the clay is extruded using a predetermined mold to form a honeycomb structure with quadrilateral compartments and a cylindrical overall shape.

[0161] 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 portion of the openings of the compartments on one end face of the honeycomb molded body is masked. The masked end is immersed in a sealing slurry containing cordierite, and then, for the other end, the openings of the sealed compartments on the aforementioned end face are masked. Then, by immersing in the sealing slurry, the sealing slurry is filled into the openings of the predetermined compartments on the outflow side end face in a grid pattern, alternating between the openings of predetermined compartments on one end face and the openings of the remaining compartments on the other end face. The honeycomb molded body filled with sealing slurry is then dried using a hot air dryer and further fired at 1410–1440°C for 5 hours, thereby producing a honeycomb filter.

[0162] The fabricated honeycomb filter has a diameter of 118 mm, a length along its central axis of 100 mm, and a cell density of 200 cpsi (31 cells / cm³). 2 The porosity of the adjacent wall is 60.0%.

[0163] 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 partition plates. During installation, a liner primarily composed of ceramic fiber is used to cover the outer periphery of both the honeycomb structure and the honeycomb filter, which are then pressed into the container for fixation. This creates an exhaust gas purification device. It should be noted that the honeycomb structure and honeycomb filter are maintained at a 50mm distance between their end faces (between the first outflow side end face and the second inflow side end face) by the partition plates.

[0164] For the manufactured exhaust gas purification device, the "NO emission (NOx emission)" is evaluated using the following method.

[0165] [Methods for measuring NOx emissions]

[0166] The exhaust gas purification devices obtained in the various embodiments and comparative examples were installed in the exhaust system of a plug-in hybrid passenger vehicle equipped with a 2.0-liter direct-injection gasoline engine, an electric motor, and a 48 kWh battery with a charge rate of less than 20%. Then, as a vehicle test using a chassis dynamometer, the emissions of nitrogen oxides in the exhaust gas were measured under the first phase of operation in the US Limited Operating Mode (FTP mode), and the emission values ​​were obtained. Nitrogen oxide emissions below 0.2 g / km were defined as acceptable ("acceptable"), and emissions of 0.2 g / km or higher were defined as unacceptable ("unacceptable").

[0167] (Example 2)

[0168] Example 2 is the same as Example 1 except that the porosity of the cellular structure's partition is changed to 50%.

[0169] (Examples 3 and 4)

[0170] Examples 3 and 4 are the same as Example 2, except that the distance between the end face of the honeycomb structure and the honeycomb filter is changed to 40mm or 30mm.

[0171] (Example 5)

[0172] In Example 5, the distance between the end face of the honeycomb structure and the honeycomb filter was set to 20 mm. An alumina water coating (low-emissivity surface) with an emissivity lower than cordierite was formed on the second inflow side end face of the honeycomb filter. Otherwise, it was the same as in Example 2. The alumina water coating was prepared by studying a catalyst coating method in which a three-way catalyst water coating was also applied to the sealing surface of the second inflow side end face of the honeycomb filter when the three-way catalyst was supported on the honeycomb filter. In this method of setting the alumina carrier water coating of the three-way catalyst on the second inflow side end face of the honeycomb filter, it also has the effect of reducing the emissivity of the second inflow side end face of the honeycomb filter. Furthermore, it has the effect of using the soot oxidation function of the three-way catalyst to instantly oxidize and remove the soot that is to be accumulated on the second inflow side end face of the honeycomb filter, thereby keeping the surface clean and reducing the emissivity of the second inflow side end face of the honeycomb filter.

[0173] (Example 7)

[0174] In Example 7, the distance between the end face of the honeycomb structure and the honeycomb filter was set to 20 mm. The surface of the sealing portion of the second inflow side end face of the honeycomb filter was smoothed to an arithmetic mean roughness Ra of less than 10 μm (low-emissivity surface). Otherwise, it was the same as in Example 2. After the catalyst was loaded onto the honeycomb filter and dried, the surface of the sealing portion was ground with a grinding stone.

[0175] (Example 8)

[0176] In Example 8, the distance between the end faces of the honeycomb structure and the honeycomb filter is set to 20mm. A stainless steel heat insulation plate is installed between the honeycomb structure and the honeycomb filter. Otherwise, it is the same as in Example 2. The heat insulation plate is a 2mm thick stainless steel plate with 25mm diameter flow paths at 7 locations and mirror-finished end faces, and is arranged perpendicular to the flow paths.

[0177] (Example 9)

[0178] In Example 9, the distance between the end face of the honeycomb structure and the honeycomb filter was set to 20 mm. A catalyst for oxidizing and removing soot was placed on the second inflow side end face of the honeycomb filter. Otherwise, it was the same as in Example 2. After the honeycomb filter in the latter section was loaded with the catalyst (three-way catalyst) and dried, an alumina-based catalyst slurry containing only platinum (Pt) as a precious metal was brush-coated onto the second inflow side end face and dried. A platinum catalyst layer (oxidation catalyst layer) with a total platinum content of 0.1 g was placed on the second inflow side end face.

[0179] (Examples 10 and 11)

[0180] Examples 10 and 11 are the same as Example 2, except that the distance between the end faces of the honeycomb structure and the honeycomb filter is set to 20 mm, and the angle between the central axis of the honeycomb structure and the central axis of the honeycomb filter is set to 20 degrees or 30 degrees.

[0181] (Example 12)

[0182] Example 12 is the same as Example 2, except that the honeycomb structure and the honeycomb filter are housed in different tanks (a first tank and a second tank), and the distance between the end faces of the honeycomb structure and the honeycomb filter is set to 300 mm. The diameter of the connecting pipe between the tanks is 40 mm, which is smaller than the diameter of the first tank and the second tank (130 mm).

[0183] (Example 13)

[0184] Example 13 is the same as Example 12 except that the diameter of the connecting pipe is set to 60mm.

[0185] (Comparative Example 1)

[0186] Comparative Example 1 is the same as Example 2, except that the distance between the end face of the honeycomb structure and the honeycomb filter is set to 20 mm.

[0187] (Comparative Example 2)

[0188] Comparative Example 2 is the same as Example 1 except that the porosity of the cellular structure partition is changed to 25%.

[0189] (Comparative Example 3)

[0190] Comparative Example 3 is the same as Example 1, except that the opening ratio of the first inflow side end face of the honeycomb structure is changed to 77%.

[0191] Examples 1 to 13 were equipped with the radiant heat reduction mechanism described in the embodiments, but Comparative Examples 1 to 3 were not equipped with the radiant heat reduction mechanism. The following table summarizes the evaluation results of various conditions and NOx emissions for Examples 1 to 13 and Comparative Examples 1 to 3.

[0192] Table 1

[0193]

[0194] In Examples 1 to 13, which were equipped with a radiant heat reduction mechanism, NOx emissions were evaluated as "acceptable." However, in Comparative Examples 1 to 3, which were not equipped with a radiant heat reduction mechanism, NOx emissions were evaluated as "unacceptable." This confirms that by equipping the radiant heat reduction mechanism, the honeycomb structure can be heated up earlier.

[0195] Symbol Explanation

[0196] 1—Electrified vehicle; 2—Motor; 4—Engine; 4a—Exhaust system; 4b—Exhaust gas; 5—Exhaust gas purification device; 6—Honeycomb structure; 7—Honeycomb filter; 8—Radiant heat reduction mechanism; 60—First honeycomb substrate; 61—First inflow side end face; 62—First outflow side end face; 63—Compartment; 64—Block; 70—Second honeycomb substrate; 71—Second inflow side end face; 72—Second outflow side end face; 73—Compartment; 74—Block; 75—Sealing part; 80—Low radiation surface; 82—Heat insulation plate; 83—Space; 84—Connecting pipe; 90—Tank; 91—First tank; 92—Second tank; 731—First compartment; 732—Second compartment.

Claims

1. An exhaust gas purification device for an electric vehicle having an engine and a motor as a power source for driving, characterized in that, have: A honeycomb structure having a first honeycomb substrate having porous partitions dividing a plurality of compartments extending from a first inflow side end face to a first outflow side end face, wherein the compartments of the first honeycomb substrate are open at both ends. as well as A honeycomb filter has a second honeycomb substrate with porous partitions dividing a plurality of compartments extending from a second inflow side end face to a second outflow side end face. The compartments of the second honeycomb substrate include a first compartment and a second compartment. The first compartment is open at the second inflow side end face and sealed at the second outflow side end face, and the second compartment is open at the second outflow side end face and sealed at the second inflow side end face. The honeycomb filter is configured in series with the honeycomb structure relative to the flow of exhaust gas. The porosity of the partition walls in the first honeycomb substrate is 40% or more. The opening ratio of the first inflow side end face of the first honeycomb substrate is 85% or more. A ternary catalyst is supported on both the first honeycomb substrate and the second honeycomb substrate. The honeycomb structure is positioned upstream of the honeycomb filter in the direction of exhaust gas flow. A radiant heat reduction mechanism is provided in at least one of the cellular structure, the cellular filter, and between the cellular structure and the cellular filter, which reduces the heat transfer caused by radiation from the cellular structure to the cellular filter.

2. The waste gas purification device according to claim 1, characterized in that, The honeycomb structure and the honeycomb filter are housed in a single container. The radiant heat reduction mechanism is a low-radiation surface disposed on at least one of the first outflow side end face of the first honeycomb substrate and the second inflow side end face of the second honeycomb substrate. The low-emissivity surface has a lower emissivity compared to the first or second honeycomb substrate in the state without the radiant heat reduction mechanism.

3. The waste gas purification device according to claim 2, characterized in that, The low-emissivity surface is composed of the surface of a layer of material with high reflectivity for mid-infrared electromagnetic waves with wavelengths of 3 to 8 μm, compared to at least one of the first inflow side end face and the second outflow side end face.

4. The waste gas purification device according to claim 2, characterized in that, The low-emissivity surface is formed by the surface of an oxygen defect-induced surface heat-treated layer.

5. The waste gas purification device according to claim 2, characterized in that, The second inflow side end face has a sealing portion for sealing the second compartment opening. The low-emissivity surface is formed by the surface of the sealing portion having an arithmetic mean roughness Ra of less than 10 μm.

6. The waste gas purification device according to claim 1, characterized in that, The radiant heat reduction mechanism is located on the second inflow side end face and is a catalyst that removes the soot adhering to the second inflow side end face by oxidation.

7. The waste gas purification device according to claim 1, characterized in that, The honeycomb structure and the honeycomb filter are housed in a single container. The radiant heat reduction mechanism is a heat insulation plate disposed between the honeycomb structure and the honeycomb filter. The heat insulation plate has multiple openings that allow exhaust gas to flow through, and has a surface with a high reflectivity for mid-infrared electromagnetic waves with wavelengths of 3 to 8 μm compared to the first inflow side end face and the second outflow side end face of the first honeycomb substrate and the second honeycomb substrate.

8. The waste gas purification device according to claim 1, characterized in that, The honeycomb structure and the honeycomb filter are housed in a single container. The radiant heat reduction mechanism is disposed between the honeycomb structure and the honeycomb filter, and is a space with a width of more than 30 mm in the direction of exhaust gas flow.

9. The waste gas purification device according to claim 8, characterized in that, An angle is provided between the central axis of the cellular structure and the central axis of the cellular filter.

10. The waste gas purification device according to claim 1, characterized in that, The honeycomb structure is housed in a first container, and the honeycomb filter is housed in a second container, which is different from the first container. The radiant heat reduction mechanism is located between the first tank and the second tank, and is a connecting pipe with a diameter smaller than that of the first tank and the second tank.

11. An electric vehicle comprising an engine and a motor as a power source for driving, characterized in that, The exhaust gas purification device according to any one of claims 1 to 10, which is provided in the exhaust system of the engine.

Images