Catalyst device

Abstract

To provide a catalyst device capable of suppressing accumulation of granular materials with a simple configuration.SOLUTION: A catalytic device comprises an annular member that forms an exhaust gas flow path, and an electrically heated catalyst housed in the annular member, and the annular member has an extension part that extends downstream of the exhaust gas flow path beyond a rear end of the electrically heated catalyst.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present disclosure relates to catalytic devices. [Background technology]

[0002] Patent Document 1 proposes a catalyst device that controls the flow of exhaust gas by providing a labyrinth structure on the peripheral surface of a case that houses a catalyst carrier, thereby suppressing the accumulation of particulate matter (PM). With the above-mentioned configuration, the catalyst device proposed in Patent Document 1 suppresses short circuits between the catalyst carrier and the case caused by particulate matter that accumulates on the surface of the case. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent Publication No. 2022-051068 Summary of the Invention [Problem to be solved by the invention]

[0004] However, the above configuration requires a complex labyrinth structure, and therefore a catalyst device that can suppress the accumulation of particulate matter with a simpler configuration is desired.

[0005] The present disclosure has been made in consideration of the above, and aims to provide a catalyst device that can suppress the accumulation of particulate matter with a simple configuration. [Means for solving the problem]

[0006] The catalytic converter according to the present disclosure comprises an annular member forming an exhaust gas flow path and an electrically heated catalyst housed in the annular member, the annular member having an extension portion extending downstream of the exhaust gas flow path beyond the rear end of the electrically heated catalyst. Effect of the Invention

[0007] According to the present disclosure, accumulation of particulate matter can be suppressed with a simple configuration. [Brief description of the drawings]

[0008] [Figure 1] FIG. 1 is a schematic diagram showing the configuration of the catalyst device according to the first embodiment. [Diagram 2] FIG. 2 is a schematic diagram showing a first modified example of the catalyst device according to the first embodiment. [Diagram 3] FIG. 3 is a schematic diagram showing a second modified example of the catalyst device according to the first embodiment. [Figure 4] FIG. 4 is a schematic diagram showing the configuration of the catalyst device according to the second embodiment. [Diagram 5] FIG. 5 is a schematic diagram showing the configuration of a catalyst device according to the third embodiment. [Figure 6] FIG. 6 is a schematic diagram showing the configuration of a catalyst device according to the fourth embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0009] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A catalytic converter according to an embodiment of the present disclosure will be described with reference to the drawings. The components in the following embodiments include those that are easily replaceable by a person skilled in the art, or those that are substantially the same.

[0010] (Embodiment 1) The configuration of a catalytic converter according to a first embodiment will be described with reference to Figs. 1 to 3. The catalytic converter according to this embodiment is, for example, an exhaust purification device arranged in an exhaust passage of a vehicle engine. As shown in Fig. 1, the catalytic converter according to this embodiment includes an electrically heated catalyst (EHC) 1, an inner tube 2, a rear catalyst 5, and an outer tube 6. Note that in this figure, only the upper half of the catalytic converter is shown with respect to an axis C passing through the center of the catalytic converter. In other words, the shape of the catalytic converter is symmetrical with respect to the axis C.

[0011] The electrically heated catalyst 1 is formed in a cylindrical shape. The electrically heated catalyst 1 is housed in an inner tube 2. The diameter of the electrically heated catalyst 1 is smaller than the diameter of the rear catalyst 5. The electrically heated catalyst 1 is provided with a catalyst carrier on which a catalyst for purifying exhaust gas is supported. The catalyst carrier is, for example, a honeycomb structure in which a plurality of passages extending in the exhaust direction are defined. Examples of the catalyst supported by the catalyst carrier include a three-way catalyst, an oxidation catalyst, and a selective reduction catalyst.

[0012] The inner pipe 2 is formed in a cylindrical shape and is made of a metal material such as stainless steel. The inner pipe 2 is an annular member that forms a flow path for exhaust gas. The inner pipe 2 is housed in the small diameter portion 61 of the outer pipe 6. That is, the inner pipe 2 is press-fitted into the outer pipe 6 via an inner pipe holding mat 4. The inner pipe 2 holds the electrically heated catalyst 1 via an electrically heated catalyst holding mat 3 made of an insulator.

[0013] The rear catalyst 5 is formed in a cylindrical shape. The rear catalyst 5 is housed in a large diameter portion 62 of an outer pipe 6. The outer pipe 6 is formed in a cylindrical shape and is made of a metal material such as stainless steel. The outer pipe 6 is an annular member that forms a flow path for exhaust gas. The outer pipe 6 includes a small diameter portion 61, a large diameter portion 62, and a tapered portion 63 that connects the small diameter portion 61 and the large diameter portion 62.

[0014] The small diameter portion 61 holds the inner pipe 2 via an inner pipe holding mat 4 made of an insulator. The large diameter portion 62 holds the rear catalyst 5 via a rear catalyst holding mat 7 made of an insulator.

[0015] Here, in a catalyst device using the electrically heated catalyst 1, it is necessary to ensure insulation performance, but for example, if soot, which is an electrical conductor, adheres to the inner surface of the inner tube 2, an electric leakage path from "electrically heated catalyst 1 to soot adhered to the inner tube 2 to the outer tube 6" is formed, and insulation performance is reduced. Therefore, in the catalyst device according to the embodiment, the above problem is solved by providing an extension 21 on the inner tube 2, which is an annular member.

[0016] The extension portion 21 is provided on the downstream side of the exhaust gas flow path in the inner pipe 2. The extension portion 21 is provided so as to extend downstream of the exhaust gas flow path beyond the rear end of the electrically heated catalyst 1. The extension portion 21 is a portion of the inner pipe 2 that extends beyond the ridge line (see the two-dot chain line) that connects the rear end of the electrically heated catalyst 1 and the front end of the rear catalyst 5, as shown in part A in FIG.

[0017] By providing such an extension 21 on the inner pipe 2, the exhaust gas that has passed through the electrically heated catalyst 1 hits the extension 21, so that "the temperature of the rear end of the inner pipe 2 is greater than the temperature of the outer pipe 6." By creating a temperature difference between the rear end of the inner pipe 2 and the outer pipe 6 in this way, the amount of soot adhering to the rear end of the inner pipe 2 can be reduced by thermophoresis. As a result, the deterioration of insulation performance can be suppressed.

[0018] (Modification) As described above, the extension portion 21 of the inner pipe 2 is intended to hit the exhaust gas that has passed through the electrically heated catalyst 1, and therefore may have a different shape. For example, as shown in Fig. 2, in order to reduce pressure loss and ensure manufacturability, an extension portion 22 having a shape bent outward (outward in the radial direction) may be used instead of the extension portion 21. Also, as shown in Fig. 3, in order to more actively hit the exhaust gas, an extension portion 23 having a shape tapered inward (inward in the radial direction) may be used instead of the extension portion 21.

[0019] (Embodiment 2) The configuration of the catalytic device according to the second embodiment will be described with reference to Fig. 4. The catalytic device according to this embodiment includes an electrically heated catalyst 1, an inner tube 2A, a rear catalyst 5, and an outer tube 6. In the following, only the parts of the catalytic device according to the second embodiment that are different from the catalytic device according to the first embodiment will be described, and the description of the other parts will be omitted.

[0020] The inner pipe 2A is formed in a cylindrical shape and is made of a metal material such as stainless steel. The inner pipe 2A is an annular member that forms a flow path for exhaust gas. The inner pipe 2A is housed in the small diameter portion 61 of the outer pipe 6. That is, the inner pipe 2A is press-fitted into the outer pipe 6 via an inner pipe holding mat 4. The inner pipe 2A holds the electrically heated catalyst 1 via an electrically heated catalyst holding mat 3 made of an insulator. The inner pipe 2A is provided with an extension 24.

[0021] The extension portion 24 is provided in the inner pipe 2A on the downstream side of the exhaust gas flow path. The extension portion 24 is provided so as to extend downstream of the exhaust gas flow path beyond the rear end of the electrically heated catalyst 1. As shown in Fig. 4, the extension portion 24 has a shape that follows a ridge line (see two-dot chain line) that connects the rear end of the electrically heated catalyst 1 and the front end of the rear catalyst 5 in the inner pipe 2A.

[0022] By providing such an extension 24 on the inner pipe 2A, the exhaust gas that has passed through the electrically heated catalyst 1 will not hit the extension 24 excessively. Therefore, it is possible to make the temperature of the rear end of the inner pipe 2A greater than the temperature of the outer pipe 6 without impeding the flow of the exhaust gas. By creating a temperature difference between the rear end of the inner pipe 2A and the outer pipe 6 in this way, the amount of soot adhering to the rear end of the inner pipe 2A can be reduced by thermophoresis. As a result, it is possible to suppress the deterioration of the insulation performance. Furthermore, by providing the extension 24 with a shape that does not impede the flow of the exhaust gas, it is possible to suppress the occurrence of pressure loss.

[0023] (Embodiment 3) The configuration of the catalytic converter according to the third embodiment will be described with reference to Fig. 5. The catalytic converter according to this embodiment includes an electrically heated catalyst 1, an inner tube 2B, a rear catalyst 5A, and an outer tube 6A. In the following, only the parts of the catalytic converter according to the third embodiment that are different from the catalytic converter according to the first embodiment will be described, and the other parts will not be described.

[0024] The inner pipe 2B is formed in a cylindrical shape and is made of a metal material such as stainless steel. The inner pipe 2B is an annular member that forms a flow path for exhaust gas. The inner pipe 2B is accommodated in the large diameter portion 62A of the outer pipe 6A. That is, the inner pipe 2B is press-fitted into the outer pipe 6A via an inner pipe holding mat 4. The inner pipe 2B holds the electrically heated catalyst 1 via an electrically heated catalyst holding mat 3 made of an insulator. The inner pipe 2B is provided with an extension 25.

[0025] The extension portion 25 is provided on the inner pipe 2B downstream of the exhaust gas flow path. The extension portion 25 is provided so as to extend downstream of the exhaust gas flow path beyond the rear end of the electrically heated catalyst 1. The extension portion 25 has a shape that is tapered inward (radially inward) in order to actively hit the exhaust gas, similar to FIG. 3 described above.

[0026] By providing such an extension 25 on the inner pipe 2B, the exhaust gas that has passed through the electrically heated catalyst 1 hits the extension 25, so that "the temperature of the rear end of the inner pipe 2B is greater than the temperature of the outer pipe 6A." By creating a temperature difference between the rear end of the inner pipe 2B and the outer pipe 6A in this way, the amount of soot adhering to the rear end of the inner pipe 2B can be reduced by thermophoresis. As a result, the deterioration of insulation performance can be suppressed.

[0027] The rear catalyst 5A is formed in a cylindrical shape. The rear catalyst 5A is housed in a large diameter portion 62A of an outer pipe 6A. The diameter of the rear catalyst 5A is formed to be equal to or smaller than the diameter of the electrically heated catalyst 1. The outer pipe 6A is formed in a cylindrical shape and is made of a metal material such as stainless steel. The outer pipe 6A is an annular member that forms a flow path for exhaust gas. The outer pipe 6A includes a small diameter portion 61A, a large diameter portion 62A, and a tapered portion 63A that connects the small diameter portion 61A and the large diameter portion 62A.

[0028] The small diameter portion 61A holds the rear catalyst 5A via a rear catalyst holding mat 7 made of an insulator, and the large diameter portion 62A holds the inner pipe 2B via an inner pipe holding mat 4 made of an insulator.

[0029] (Embodiment 4) The configuration of the catalytic converter according to the fourth embodiment will be described with reference to Fig. 6. The catalytic converter according to this embodiment includes an electrically heated catalyst 1, an inner tube 2B, and an outer tube 6B. In the following, only the parts of the catalytic converter according to the fourth embodiment that are different from the catalytic converter according to the third embodiment will be described, and the description of the other parts will be omitted.

[0030] The catalytic converter according to this embodiment does not include a rear catalyst, and only includes an electrically heated catalyst 1. In addition, an extension 25 is provided on the inner pipe 2B.

[0031] The extension portion 25 is provided on the inner pipe 2B downstream of the exhaust gas flow path. The extension portion 25 is provided so as to extend downstream of the exhaust gas flow path beyond the rear end of the electrically heated catalyst 1. The extension portion 25 has a shape that is tapered inward (radially inward) in order to actively hit the exhaust gas, similar to FIG. 3 described above.

[0032] By providing such an extension 25 on the inner pipe 2B, the exhaust gas that has passed through the electrically heated catalyst 1 hits the extension 25, so that "the temperature of the rear end of the inner pipe 2B is greater than the temperature of the outer pipe 6B." By creating a temperature difference between the rear end of the inner pipe 2B and the outer pipe 6B in this way, the amount of soot adhering to the rear end of the inner pipe 2B can be reduced by thermophoresis. As a result, the deterioration of insulation performance can be suppressed.

[0033] The outer pipe 6B is formed in a cylindrical shape and is made of a metal material such as stainless steel. The outer pipe 6B is an annular member that forms a flow path for exhaust gas. The outer pipe 6B holds the inner pipe 2B via an inner pipe holding mat 4 made of an insulator. The outer pipe 6B is connected to a cone or the like for reducing the pipe. The cone or the like is connected to a tail pipe or the like.

[0034] In the catalytic converter according to the embodiment described above, the extension portions 21, 22, 23, 24, and 25 extending downstream of the exhaust gas flow path are provided, so that the exhaust gas can easily come into contact with the extension portions 21, 22, 23, 24, and 25. In addition, heating of the extension portions 21, 22, 23, 24, and 25 is promoted, and a temperature gradient is generated around the extension portions 21, 22, 23, 24, and 25.

[0035] As a result, particulate matter such as soot moves from the extensions 21, 22, 23, 24, and 25 by thermophoresis, and therefore adhesion of particulate matter to the extensions 21, 22, 23, 24, and 25 (=annular members) can be suppressed. Therefore, according to the catalyst device of the embodiment, the accumulation of particulate matter can be suppressed by a simple configuration in which the extensions 21, 22, 23, 24, and 25 are simply provided.

[0036] Further advantages and modifications may readily occur to those skilled in the art. Thus, the invention in its broader aspects is not limited to the specific details and representative embodiments shown and described above. Accordingly, various modifications may be made without departing from the spirit or scope of the general inventive concept as defined by the appended claims and equivalents thereof. [Explanation of symbols]

[0037] 1 Electrically Heated Catalyst (EHC) 2,2A,2B Inner pipe 21,22,23,24,25 Extension part 3 Electrically heated catalyst support mat 4 Inner tube holding mat 5,5A post-catalyst 6,6A,6B outer tube 61,61A Small diameter part 62,62A Large diameter section 63,63A Tapered section 7 Rear catalyst support mat C axis

Claims

[Claim 1] an annular member that forms an exhaust gas flow path; an electrically heated catalyst housed in the annular member; Equipped with the annular member has an extension portion that extends downstream of the rear end of the electrically heated catalyst in the exhaust gas flow path, Catalytic device.

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