Exhaust purifier

Abstract

It suppresses the occurrence of deposits. [Solution] The exhaust gas purification device comprises an exhaust pipe, a mounting portion for a device that supplies urea water to the exhaust gas flow path within the exhaust pipe, an exhaust gas purification member located downstream of the mounting portion, a plurality of structures, and a covering structure. Each structure is provided on the outer circumferential surface of the exhaust pipe between the mounting portion and the purification member. The covering structure has an outer pipe portion that forms the outer circumferential surface of the exhaust pipe and an inner pipe portion that faces the inner circumferential surface of the outer pipe portion while being separated from the outer pipe portion. Each structure is provided on the outer circumferential surface of the outer pipe portion in the covering structure. The inner pipe portions are arranged to face each structure.

Description

Technical Field

[0001] The present disclosure relates to an exhaust purification device.

Background Art

[0002] As disclosed in Patent Document 1, there is known an exhaust purification device that purifies nitrogen oxides contained in exhaust gas by injecting urea water into exhaust gas flowing down an exhaust pipe and bringing the exhaust gas mixed with urea water into contact with an SCR catalyst.

Prior Art Literature

Patent Literature

[0003]

Patent Document 1

Summary of the Invention

Problem to be Solved by the Invention

[0004] However, when a structure such as a flange is provided in the exhaust pipe, heat dissipation proceeds through the structure. Therefore, when such a structure is provided on the downstream side of the urea water injection nozzle, the temperature of a portion of the inner circumferential surface of the exhaust pipe that comes into contact with urea water decreases. As a result, the urea water is not sufficiently evaporated and decomposed, which may cause deposits to form around the portion.

[0005] One aspect of the present disclosure is that it is desirable to suppress the generation of deposits.

Means for Solving the Problem

[0006] One aspect of the present disclosure is an exhaust gas purification device configured to purify the exhaust gas of an internal combustion engine, comprising an exhaust pipe, a mounting portion, a purification member, a plurality of structures, and a covering structure. The exhaust pipe forms an exhaust gas flow path. The mounting portion is a part provided on the exhaust pipe to which a device for supplying urea water toward the exhaust gas flow path is attached. The purification member is provided downstream of the mounting portion in the exhaust gas flow path and purifies the exhaust gas. Each structure is provided between the mounting portion and the purification member on the outer circumferential surface of the exhaust pipe. The covering structure is provided on the exhaust pipe and has an outer pipe portion and an inner pipe portion. The outer pipe portion is a tubular portion that forms the outer circumferential surface of the exhaust pipe. The inner pipe portion is a tubular member arranged to face the inner circumferential surface of the outer pipe portion while being separated from the outer pipe portion. Each structure is provided on the outer circumferential surface of the outer pipe portion in the covering structure. The inner pipe portion is arranged to face each structure.

[0007] According to the above configuration, the opposite side of each structure in the exhaust pipe is covered by the inner pipe section of the covering structure. Therefore, the temperature drop around each structure can be suppressed, and the formation of deposits due to urea solution can be suppressed.

[0008] In one aspect of this disclosure, the exhaust pipe may have an upstream exhaust pipe and a downstream exhaust pipe. The upstream exhaust pipe is provided with a mounting portion. The downstream exhaust pipe has a purification member arranged therein. The downstream end of the upstream exhaust pipe may be provided with an upstream flange, which is a structural component. The upstream end of the downstream exhaust pipe may be provided with a downstream flange, which is a structural component. The upstream and downstream exhaust pipes may be connected via the upstream flange and the downstream flange. The inner pipe portion may be arranged to face the upstream flange and the downstream flange.

[0009] According to the above configuration, the portion of the upstream exhaust pipe opposite the upstream flange and the portion of the downstream exhaust pipe opposite the downstream flange are covered by the inner pipe portion of the covering structure. Therefore, temperature drops around the upstream and downstream flanges can be suppressed, and the formation of deposits due to urea solution can be suppressed.

[0010] In one aspect of this disclosure, the upstream end of the inner pipe section may be located upstream of each structure, and the downstream end may be located downstream of each structure. With the above configuration, the temperature drop around each structure can be suppressed more reliably. Therefore, the formation of deposits caused by urea solution can be suppressed even further.

[0011] In one aspect of this disclosure, the cross-section of the inner pipe portion perpendicular to the exhaust flow direction may be smaller than the cross-section of the portion adjacent to the upstream side of the inner pipe portion in the exhaust pipe. According to the above configuration, the outer diameter of the exhaust pipe cross-section can be suppressed. Therefore, it is possible to miniaturize the exhaust gas purification device.

[0012] One aspect of the present disclosure may further include an upstream heat shield facing the outer circumferential surface of the upstream exhaust pipe with a gap between them. The downstream end of the upstream heat shield may be positioned to face the inner pipe.

[0013] With the above configuration, the portion of the upstream exhaust pipe that does not face the inner pipe can be more preferably covered from the outer surface side by the upstream heat shield. Therefore, heat radiation from the upstream exhaust pipe can be more preferably suppressed.

[0014] One aspect of this disclosure may further include a downstream heat shield facing the outer circumferential surface of the downstream exhaust pipe with a gap between them. The downstream heat shield may be positioned so that its upstream end faces the inner pipe.

[0015] With the above configuration, the portion of the downstream exhaust pipe that does not face the inner pipe can be more preferably covered from the outer surface side by the downstream heat shield. Therefore, heat radiation from the downstream exhaust pipe can be more preferably suppressed.

[0016] In one aspect of this disclosure, the upstream exhaust pipe may have an outlet portion which includes the downstream end, and a main body portion which is adjacent to the upstream side of the outlet portion and is integrally molded with the outlet portion. The outlet portion may form an inner pipe portion in the covering structure.

[0017] According to the above configuration, since formation of a joint between the outlet portion and the main body portion in the upstream exhaust pipe can be suppressed, formation of a step on the inner circumferential surface of the upstream exhaust pipe can be suppressed. Therefore, deposition of deposits on the inner circumferential surface of the upstream exhaust pipe can be suppressed. [Brief Description of the Drawings]

[0018] [Figure 1] It is a cross-sectional view of the exhaust purification device according to the first embodiment, the cross-section being parallel to and including an axis A. [Figure 2] It is a cross-sectional view of the exhaust purification device according to the second embodiment, the cross-section being parallel to and including an axis A. [Figure 3] It is a cross-sectional view of the exhaust purification device according to the third embodiment, the cross-section being parallel to and including an axis A. [Figure 4] It is a cross-sectional view of the exhaust purification device according to the fourth embodiment, the cross-section being parallel to and including an axis A. [Mode for Carrying Out the Invention]

[0019] Hereinafter, embodiments to which the present disclosure is applied will be described with reference to the drawings. [1. First Embodiment] [(1) Overview] The exhaust purification device 1 of the first embodiment is provided in an exhaust flow path generated in an internal combustion engine, and is configured to purify exhaust gas with urea water (see FIG. 1). Note that the exhaust purification device 1 and the internal combustion engine may, for example, be mounted on a vehicle. Further, the internal combustion engine may be a diesel engine. Further, hereinafter, the upstream side and the downstream side in the exhaust flow direction are simply referred to as the upstream side and the downstream side. The exhaust purification device 1 includes an exhaust pipe 2, an upstream insulator 5, a downstream insulator 6, a purification member 44, an injector 7, and a mixer 8.

[0020] [(2) Exhaust Pipe] The exhaust pipe 2 constitutes a part of an exhaust flow path from an internal combustion engine and extends along the axis A (see FIG. 1). Hereinafter, a cross section orthogonal to the axis A is simply referred to as a cross section. The axis A passes through the center of said cross section of the exhaust pipe 2. Also, a radial direction of a circle centered on the axis A is simply referred to as a radial direction. The exhaust pipe 2 includes an upstream-side exhaust pipe 3 and a downstream-side exhaust pipe 4, and is provided with a covering structure 10.

[0021] [(3) Upstream-side Exhaust Pipe] The upstream-side exhaust pipe 3 has a circular cross section, and includes a main body portion 30, a mounting portion 31, an outlet portion 32, an upstream-side outer peripheral portion 34, and an upstream-side flange 35 (see FIG. 1).

[0022] <Main Body Portion> The main body portion 30 is a tubular portion having a curved section 30A and a straight section 30B that extends straight from the downstream end of the curved section 30A (see FIG. 1). The straight section 30B has a constant cross-sectional diameter.

[0023] <Mounting Portion> The mounting portion 31 is a portion for mounting an injector 7, and has a hole that communicates the inside and the outside of the main body portion 30 (see FIG. 1). The mounting portion 31 is provided on the outer peripheral side of the curved section 30A of the main body portion 30.

[0024] <Outlet Portion> The outlet portion 32 has a circular cross section, and is a tubular portion that extends straight in the same direction as the straight section 30B (see FIG. 1). The outlet portion 32 extends from the downstream end of the straight section 30B of the main body portion 30 and forms the downstream end of the upstream-side exhaust pipe 3. As will be described later in detail, the downstream end of the outlet portion 32 is located more downstream than the downstream end of the upstream-side outer peripheral portion 34.

[0025] The diameter of the cross-section of the outlet section 32 is smaller than the diameter of the cross-section of the straight section 30B, and the portion around the upstream end of the outlet section 32 forms a reduced diameter section 33. That is, the reduced diameter section 33 is a portion where the diameter of the cross-section gradually decreases as you move downstream, and is tapered as an example. However, it is not limited to this, and the reduced diameter section 33 may be formed in a stepped shape, for example. In addition, the diameter of the cross-section is constant in the portion of the outlet section 32 other than the reduced diameter section 33.

[0026] Furthermore, the outlet portion 32 and the main body portion 30 are integrally molded. Specifically, these parts may be formed as an integrated component, for example, by press molding. <Outer perimeter on the upstream side> The upstream outer circumference 34 is a straight, tubular portion that surrounds the main body 30 and outlet 32 ​​of the upstream exhaust pipe 3 from the outside, and has a circular cross-section (see Figure 1). The diameter of the cross-section of the upstream outer circumference 34 is constant.

[0027] The upstream end portion of the upstream outer circumference 34 is joined to the downstream end portion of the straight section 30B, for example, by a full-circumference weld W. The full-circumference weld 11 is the portion formed by performing full-circumference welding on these portions.

[0028] <Upstream flange> The upstream flange 35 is provided so as to surround the downstream opening of the upstream outer circumference 34, and the upstream end of the upstream flange 35 is joined to the outer surface of the upstream outer circumference 34 by a full-circumferential weld W, for example (see Figure 1).

[0029] [(4) Downstream exhaust pipe] The downstream exhaust pipe 4 is a tubular member, with a circular cross-section as an example, and extends straight in the same direction as the straight section B of the main body 30 (see Figure 1). Of course, the shape of the cross-section is not limited to a circle, but can have various shapes such as a roughly circular or elliptical shape. The downstream exhaust pipe 4 comprises an inlet section 40, a tapered section 41, a housing section 42, and a downstream flange 43.

[0030] The inlet portion 40 is a tubular section that forms the upstream opening of the downstream exhaust pipe 4. The cross-section of the inlet portion 40 is circular, and the diameter of the cross-section is constant. Furthermore, the diameter of the cross-section of the inlet portion 40 is the same as that of the upstream outer circumference portion 34.

[0031] The tapered section 41 is a tubular portion extending from the downstream end of the inlet section 40. The tapered section 41 is tapered, and the diameter of its cross-section increases towards the downstream side. The housing section 42 is a tubular portion extending from the downstream end of the tapered section 41, and the purification member 44 is housed inside it.

[0032] The downstream flange 43 is provided so as to surround the upstream opening of the inlet portion 40, and the downstream end of the downstream flange 43 is joined to the outer surface of the inlet portion 40 by a full-circumferential weld W, for example.

[0033] [(5) Covering structure] The upstream flange 35 of the upstream exhaust pipe 3 is joined to the downstream flange 43 of the downstream exhaust pipe 4 (see Figure 1). The upstream flange 35 and the downstream flange 43 may be welded together or fastened together with bolts. This connects the downstream opening of the upstream exhaust pipe 3, more specifically, the downstream opening of the upstream outer circumference 34, to the upstream opening of the inlet 40 of the downstream exhaust pipe 4.

[0034] Furthermore, a covering structure 10 is formed on the inside of the upstream flange 35 and the downstream flange 43 of the exhaust pipe 2. Specifically, in the upstream exhaust pipe 3, the downstream end of the upstream outer circumference 34 faces radially toward the outer surface of the outlet 32. In other words, the outlet 32 ​​protrudes from the downstream opening of the upstream outer circumference 34, and this protruding portion is inserted into the inlet 40 of the downstream exhaust pipe 4.

[0035] In other words, the outlet section 32 is positioned inside the connected upstream outer circumference 34 and inlet section 40, and a double pipe is formed by the upstream outer circumference 34 and inlet section 40 and the outlet section 32. The upstream outer circumference 34 and inlet section 40 form the outer pipe section of the double pipe and also form the outer surface of the exhaust pipe 2. The outlet section 32 forms the inner pipe section of the double pipe, and the outer surface of the outlet section 32 faces the inner surfaces of the upstream outer circumference 34 and inlet section 40 with a gap between them, and this gap encircles the outlet section 32.

[0036] For example, the outlet section 32, the upstream outer periphery section 34, and the inlet section 40 are arranged in a concentric circle. Furthermore, the upstream end of the outlet section 32 is located upstream of the upstream flange 35. More specifically, the downstream end of the reduced diameter section 33 of the outlet section 32 is located upstream of the upstream flange 35. Also, the downstream end of the outlet section 32 is located downstream of the downstream flange 43.

[0037] [(6) Upstream Insulator] The upstream insulator 5 is a component for suppressing heat dissipation from the upstream exhaust pipe 3 (see Figure 1). The upstream insulator 5 is, for example, a tubular component and is provided so as to surround the main body 30 and the upstream outer circumference 34 of the upstream exhaust pipe 3 from the outside. The upstream insulator 5 comprises an upstream heat shield portion 50 and a joint portion 51.

[0038] The upstream heat shield 50 faces the straight section 30B of the main body 30 of the upstream exhaust pipe 3 with a gap between them, and a gap surrounding the straight section 30B is formed between the upstream heat shield 50 and the straight section 30B.

[0039] The joint 51 is an annular portion adjacent to the downstream end of the upstream heat shield 50, and is joined to the outer surface of the upstream outer circumference 34 of the upstream exhaust pipe 3 by a full-circumferential weld W, for example.

[0040] Furthermore, the joint portion 51 is positioned so that its entirety faces radially toward the outlet portion 32 of the covering structure 10. Also, the downstream end of the upstream heat shield portion 50 faces radially toward the outlet portion 32.

[0041] Of course, this is not the only option; the position of the joint 51 may also be adjusted so that the downstream end of the upstream heat shield 50 faces the straight section 30B. Furthermore, the portion of the upstream heat shield 50 adjacent to the joint 51 is provided with an enlarged diameter section 50A, in which the diameter of the cross-section gradually increases as it moves upstream. This creates a gap between the upstream heat shield 50 and the straight section 30B. However, the enlarged diameter section 50A is not limited to this, and may have a shape in which the diameter of the cross-section increases in a stepped manner.

[0042] Furthermore, the upstream insulator 5 is joined to the upstream exhaust pipe 3 by a joint 51 located around its downstream end. However, the design is not limited to this; a joint may be provided around the upstream end of the upstream insulator 5, and the upstream insulator 5 may be joined to the upstream exhaust pipe 3 by this joint. Even in such a case, it is desirable that the downstream end of the upstream heat shield 50 faces radially to the outlet 32 ​​of the covering structure 10.

[0043] [(7) Downstream insulator] The downstream insulator 6 is a component for suppressing heat dissipation from the downstream exhaust pipe 4 (see Figure 1). The downstream insulator 6 is, for example, a tubular component and is installed so as to surround the downstream exhaust pipe 4 from the outside. The downstream insulator 6 comprises a downstream heat shield portion 60 and a joint portion 61.

[0044] The downstream heat shield section 60 faces the inlet section 40, tapered section 41, and housing section 42 of the downstream exhaust pipe 4 with a gap between them, and a gap is formed between the downstream heat shield section 60 and these sections, surrounding these sections. The downstream heat shield section 60 has an inclined section 60A that slopes so that the diameter of the cross-section increases as it moves downstream, and a straight section 60B adjacent to the downstream side of the inclined section 60A, in which the diameter of the cross-section is constant. The inclined section 60A faces the inlet section 40 and tapered section 41, and the straight section 60B faces the housing section 42.

[0045] The joint 61 is an annular portion adjacent to the upstream end of the downstream heat shield 60, and is joined to the outer surface of the inlet 40 of the downstream exhaust pipe 4 by a full-circumferential weld W, for example. Furthermore, the joint portion 61 is positioned so that its entirety faces radially toward the outlet portion 32 of the covering structure 10. In addition, the upstream end of the downstream heat shield portion 60 faces radially toward the outlet portion 32.

[0046] Of course, this is not the only option; the position of the joint 61 may also be adjusted so that the upstream end of the downstream heat shield 60 is located downstream of the outlet 32. Furthermore, the downstream insulator 6 is joined to the downstream exhaust pipe 4 by a joint 61 located around its upstream end. However, the design is not limited to this; a joint may also be provided around the downstream end of the downstream insulator 6, and the downstream insulator 6 may be joined to the downstream exhaust pipe 4 by this joint. Even in such a case, it is desirable that the upstream end of the downstream heat shield 60 faces radially to the outlet 32 ​​of the covering structure 10.

[0047] [(8) Other components] The purification element 44 is configured as an SCR catalyst and is located in the housing section 42 of the downstream exhaust pipe 4 (see Figure 1).

[0048] Furthermore, the mixer 8 is provided between the purification member 44 and the injector 7, which will be described later. For example, the mixer 8 is provided inside the straight section 30B of the main body 30 in the upstream exhaust pipe 3, and is equipped with a plurality of blades for stirring the fluid passing through the mixer 8. Furthermore, the injector 7 is attached to the mounting portion 31 of the upstream exhaust pipe 3 and supplies urea to the exhaust flow path by injecting urea toward the mixer 8 in the straight section 30B.

[0049] The urea injected from the injector 7 is then mixed with the exhaust gas by the mixer 8 to form ammonia. As the ammonia and exhaust gas pass through the purification member 44, nitrogen oxides contained in the exhaust gas are reduced, thereby purifying the exhaust gas.

[0050] [2. Second Embodiment] [(1) Overview] The exhaust gas purification device 1 of the second embodiment differs from the first embodiment in the outlet portion 32, the upstream outer circumference portion 34, and the upstream flange 35 of the upstream exhaust pipe 3, as well as the upstream insulator 5 (see Figure 2). The differences between the exhaust gas purification device 1 of the second embodiment and the first embodiment will be described below.

[0051] [(2) Exit part] In the second embodiment, the straight section 30B and outlet section 32 of the main body 30 of the upstream exhaust pipe 3 are formed as a tubular portion that extends straight and has a constant diameter in cross-section (see Figure 2). In other words, as in the first embodiment, the outlet section 32 and the main body 30 are integrally molded.

[0052] [(3) Upstream insulator] In the second embodiment, the upstream insulator 5 is formed as a tubular portion with a constant cross-sectional diameter that extends straight in the same direction as the straight section 30B of the main body 30 of the upstream exhaust pipe 3 (see Figure 2). The upstream insulator 5 is provided so as to surround the straight section 30B and the outlet section 32 from the outside.

[0053] The inner surface of the upstream insulator 5 is joined to the outer surface of the upstream exhaust pipe 3 by a joining member 52. Specifically, the joining member 52 is, for example, a short tubular member formed in a tapered shape, with the diameter of the cross-section increasing towards the downstream side.

[0054] An annular inner joint portion 52A is provided at the upstream end of the joining member 52, and the inner joint portion 52A is joined to the downstream end of the straight section 30B of the main body portion 30 by a full-circumference weld portion W. In other words, the outlet portion 32 is located downstream of the inner joint portion 52A.

[0055] Furthermore, the downstream end of the joining member 52 is provided with an annular outer joining portion 52B, which is joined to the downstream end of the straight section 30B of the main body portion 30 by a full-circumference weld portion W. The downstream portion of the outer joining portion 52B of the upstream insulator 5 forms the upstream outer circumference portion 34.

[0056] Furthermore, the portion of the upstream insulator 5 adjacent to the upstream side of the outer joint portion 52B forms the upstream heat shield portion 50. That is, the upstream heat shield portion 50 faces the straight section 30B with a gap between them, similar to the first embodiment. Also, the downstream end of the upstream heat shield portion 50 faces the outlet portion 32 in the radial direction.

[0057] The shape of the joining member 52 is not limited to those described above; for example, it may be tapered, with the diameter of the cross-section increasing towards the upstream side. Furthermore, the joining member 52 may be a member having an annular wall portion projecting radially. In this case, an inner joining portion and an outer joining portion may be provided similarly on the inner and outer edges of the wall portion.

[0058] [(4) Upstream flange] The upstream flange 35 is provided so as to surround the downstream opening of the upstream outer circumference 34, and the upstream end of the upstream flange 35 is joined to the outer surface of the upstream outer circumference 34 by a full-circumferential weld W, for example (see Figure 2).

[0059] [(5) Covering structure] In the second embodiment as well, the upstream flange 35 of the upstream exhaust pipe 3 is joined to the downstream flange 43 of the downstream exhaust pipe 4 (see Figure 2). This connects the downstream opening of the upstream outer circumference 34 of the upstream exhaust pipe 3 to the upstream opening of the inlet 40 of the downstream exhaust pipe 4.

[0060] Furthermore, similar to the first embodiment, a covering structure 10 is formed on the inside of the upstream flange 35 and the downstream flange 43. That is, the outlet portion 32 is positioned inside the connected upstream outer circumference portion 34 and inlet portion 40, and a double pipe is formed by the upstream outer circumference portion 34 and inlet portion 40 and the outlet portion 32. The upstream outer circumference portion 34 and inlet portion 40 form the outer pipe portion of the double pipe and also form the outer surface of the exhaust pipe 2. Also, similar to the first embodiment, the outlet portion 32 forms the inner pipe portion of the double pipe.

[0061] Furthermore, the upstream end of the outlet section 32 is located upstream of the upstream flange 35. Also, similar to the first embodiment, the downstream end of the outlet section 32 is located downstream of the downstream flange 43.

[0062] [3. Third Embodiment] [(1) Overview] The exhaust gas purification device 1 of the third embodiment differs from the first embodiment in the configuration of the outlet portion 32 of the upstream exhaust pipe 3, the provision of a downstream outer peripheral portion 45 on the downstream exhaust pipe 4, the downstream flange 43, and the downstream insulator 6 (see Figure 3). The differences between the exhaust gas purification device 1 of the third embodiment and the first embodiment will be described below.

[0063] [(2) Outlet section of the upstream exhaust pipe] In the upstream exhaust pipe 3 of the third embodiment, the downstream end of the outlet section 32 faces radially with respect to the downstream end of the upstream outer circumference section 34 (see Figure 3). In other words, the downstream end of the outlet section 32 is in the same position as the downstream end of the upstream outer circumference section 34 in the direction of axis A.

[0064] [(3) Downstream outer perimeter] The downstream outer circumference 45 is provided on the downstream exhaust pipe 4 so as to surround the inlet 40 from the outside (see Figure 3). The downstream outer circumference 45 is a tubular portion that extends straight in the same direction as the inlet 40, and as an example, its cross-section is circular and the diameter of the cross-section is constant. Of course, it is not limited to this, and the shape of the cross-section can be various shapes other than circular, such as approximately circular or elliptical.

[0065] The upstream end of the downstream outer circumference 45 faces the upstream end of the inlet 40 in the radial direction. In other words, the upstream end of the downstream outer circumference 45 is in the same position as the upstream end of the inlet 40 in the direction of axis A.

[0066] Furthermore, a joint portion 45A, which is an annular section, is provided around the downstream end of the downstream outer circumference portion 45, and the joint portion 45A is joined to the tapered portion 41 by a full-circumference weld portion W, for example.

[0067] [(4) Downstream flange] The downstream flange 43 is provided so as to surround the upstream opening in the downstream outer circumference 45, and the downstream end of the downstream flange 43 is joined to the outer surface of the downstream outer circumference 45 by a full-circumferential weld W, for example (see Figure 3).

[0068] [(5) Covering structure] In the third embodiment, the upstream flange 35 of the upstream exhaust pipe 3 is joined to the downstream flange 43 of the downstream exhaust pipe 4 (see Figure 3). This connects the downstream opening of the upstream outer circumference 34 of the upstream exhaust pipe 3 with the upstream opening of the downstream outer circumference 45 of the downstream exhaust pipe 4. Furthermore, the downstream opening of the outlet 32 ​​of the upstream exhaust pipe 3 and the upstream opening of the inlet 40 of the downstream exhaust pipe 4 are in substantial contact, and the outlet 32 ​​and inlet 40 are positioned adjacent to each other. Of course, this is not the only configuration; there may be gaps between these openings, and if the diameters of these openings are different, the smaller diameter opening of the outlet 32 ​​and inlet 40 may be positioned inside the other opening.

[0069] Then, similar to the first embodiment, a covering structure 10 is formed on the inside of the upstream flange 35 and the downstream flange 43. That is, the outlet portion 32 and the inlet portion 40 are arranged inside the connected upstream outer periphery 34 and the downstream outer periphery 45, and a double pipe is formed by the upstream outer periphery 34 and the downstream outer periphery 45 and the inlet portion 40 and the outlet portion 32. The upstream outer periphery 34 and the downstream outer periphery 45 form the outer pipe portion of the double pipe, similar to the first embodiment. The inlet portion 40 and the outlet portion 32 form the inner pipe portion of the double pipe, similar to the first embodiment.

[0070] Furthermore, the upstream end of the outlet section 32 is located upstream of the upstream flange 35. Also, the downstream end of the inlet section 40 is located downstream of the downstream flange 43. [(6) Downstream Insulator] The downstream insulator 6 of the third embodiment is configured in the same way as the first embodiment, and includes a downstream heat shield portion 60 and a joint portion 61, but the position where the joint portion 61 is joined is different (see Figure 3).

[0071] In other words, in the third embodiment, the joint 61 is joined to the outer circumferential surface of the downstream outer circumferential portion 45 of the downstream exhaust pipe 4 by, for example, a full-circumferential weld W. The entire joint 61 is positioned to face radially with respect to the inlet portion 40 of the covering structure 10. The upstream end of the downstream heat shield portion 60 also faces radially with respect to the inlet portion 40. Of course, this is not the only option, and the position of the joint 61 may be adjusted so that the upstream end of the downstream heat shield portion 60 is located downstream of the inlet portion 40.

[0072] [4. Fourth Embodiment] [(1) Overview] The exhaust gas purification device 1 of the fourth embodiment differs from the first embodiment in that the exhaust pipe 2 is formed as an integrated tubular portion, and instead of the upstream flange 35 and downstream flange 43, a stay 21 and a boss 22 are provided on the exhaust pipe 2 (see Figure 4). Furthermore, the exhaust gas purification device 1 of the fourth embodiment differs from the first embodiment in its covering structure 10.

[0073] [(2) Exhaust pipe] The exhaust pipe 2 has a curved section 2A and a straight section 2B that extends straight from the downstream end of the curved section 2A (see Figure 4). The downstream side of the straight section 2B of the exhaust pipe 2 is provided with a tapered section and a housing section (not shown) similar to those in the downstream exhaust pipe 4 of the first embodiment.

[0074] Similar to the first embodiment, a mounting portion 20 is provided in the curved section 2A, and a urea solution injector 7 is provided in the mounting portion 20. In addition, a mixer similar to the first embodiment may be provided upstream of the covering structure 10 in the straight section 2B. Furthermore, a purification member similar to the first embodiment is arranged in the housing section. And, similar to the first embodiment, exhaust gas is purified by supplying urea from the injector 7.

[0075] [(3) Stays and bosses] The stay 21 is an elongated member for supporting the exhaust pipe 2 (see Figure 4). A joint 21A is provided at the lower end of the stay 21, which is welded to the outer surface of the straight section 2B of the exhaust pipe 2. The upper end of the stay 21 is joined to the vehicle body, for example, and the stay 21 supports the exhaust pipe 2 from above.

[0076] Furthermore, the boss 22 is a cylindrical member for attaching components such as sensors to the exhaust pipe 2. A hole 22A is provided in the straight section 2B of the exhaust pipe 2, and the boss 22 is joined around the hole 22A on the outer surface of the straight section 2B.

[0077] As an example, the joint 21A of the stay 21 and the boss 22 are positioned opposite each other across axis A. However, the positions of the joint 21A of the stay 21 and the boss 22 can be determined as appropriate. In addition, other structures may be joined to the exhaust pipe 2, in addition to the stay 21 and the boss 22.

[0078] [(4) Covering structure] In the exhaust gas purification device 1 of the fourth embodiment, a covering structure 10 is provided inside the stay 21 and boss 22 of the exhaust pipe 2 (see Figure 4).

[0079] In other words, an inner circumferential portion 23 is provided on the inner circumferential surface of the exhaust pipe 2. The inner circumferential portion 23 has a circular cross-section and is a tubular portion that extends straight in the same direction as the straight section 2B, and comprises a joint portion 23A, a reduced diameter portion 23B, and a base portion 23C.

[0080] The joint 23A is a tubular portion located around the upstream end of the inner circumference 23 and is welded to the inner surface of the exhaust pipe 2. The reduced-diameter portion 23B is a tubular section provided adjacent to the downstream end of the joint portion 23A, and its cross-sectional diameter decreases as it moves downstream. The reduced-diameter portion 23B is tapered as an example, but is not limited to this and may be stepped.

[0081] The base portion 23C is provided adjacent to the downstream end of the reduced diameter portion 23B and forms the downstream end of the inner circumference portion 23. The base portion 23C faces radially with respect to the joint portion 21A and the boss 22 of the stay 21.

[0082] In other words, the portion of the exhaust pipe 2 where the stay 21 and boss 22 are provided and the base portion 23C form a double pipe (in other words, a covering structure 10). The exhaust pipe 2 forms the outer pipe portion of the double pipe. The base portion 23C forms the inner pipe portion of the double pipe, and the outer surface of the base portion 23C faces the inner surface of the exhaust pipe 2 with a gap between them, and this gap encircles the base portion 23C. Furthermore, the base portion 23C and the exhaust pipe 2 are arranged concentrically, as an example.

[0083] Furthermore, the upstream end of the base portion 23C is located upstream of the joint portion 21A and boss 22 of the stay 21. Also, the downstream end of the base portion 23C is located downstream of the joint portion 21A and boss 22 of the stay 21.

[0084] [(5) Variant] In the exhaust gas purification device 1 of the fourth embodiment, an upstream insulator and a downstream insulator may be provided on the upstream and downstream sides of the stay 21 and boss 22, respectively, in the same manner as in the first to third embodiments.

[0085] [5. Effects] (1) According to the above embodiment, the parts of each structure in the exhaust pipe 2 that are opposite to the flanges 35, 43, stays 21, bosses 22, etc. are covered by the inner tube portion of the covering structure 10, so that the temperature drop around each structure in the exhaust flow path can be suppressed. In addition, although these parts are relatively prone to temperature drop, the inner tube portion can prevent urea solution from directly contacting these parts. Therefore, the generation of deposits due to urea solution can be suppressed.

[0086] Furthermore, by suppressing the temperature drop around each structure, the initial warm-up of the purification member 44 can be effectively performed when a vehicle equipped with the exhaust purification device 1 starts operation, thereby improving the purification performance.

[0087] (2) Specifically, in the first to third embodiments, the portion of the upstream exhaust pipe 3 opposite the upstream flange 35 and the portion of the downstream exhaust pipe 4 opposite the downstream flange 43 are covered by the inner pipe portion of the covering structure 10 (i.e., the outlet portion 32 or the inlet portion 40). This suppresses temperature drops around the upstream flange 35 and the downstream flange 43, and suppresses the generation of deposits due to urea solution. In particular, it is difficult to cover the flanges of the exhaust pipes from the outside with insulators or the like. However, by providing the covering structure 10, deposits can be effectively suppressed.

[0088] (3) In addition, in the first and second embodiments, the upstream end of the outlet portion 32, which is the inner pipe portion of the covering structure 10, is located upstream of the upstream flange 35, and the downstream end of the outlet portion 32 is located downstream of the downstream flange 43.

[0089] Furthermore, in the third embodiment, the upstream end of the outlet section 32, which is the inner pipe section of the covering structure 10, is located upstream of the upstream flange 35, and the downstream end of the inlet section 40, which is also the inner pipe section, is located downstream of the downstream flange 43.

[0090] Furthermore, in the fourth embodiment, the upstream end of the base portion 23C, which is the inner tube portion of the covering structure 10, is located upstream of the joint portion 21A and boss 22 of the stay 21, and the downstream end of the base portion 23C is located downstream of the joint portion 21A and boss 22 of the stay 21.

[0091] Therefore, the entire area of ​​the exhaust pipe 2 where each structure is installed can be covered by the inner pipe section. Consequently, the temperature drop around each structure can be suppressed more reliably. As a result, the formation of deposits due to urea solution can be suppressed even further.

[0092] (4) Furthermore, in the upstream exhaust pipe 3 of the first and third embodiments, the diameter of the cross-section of the outlet portion 32 is smaller than the diameter of the cross-section of the straight section 30B of the main body portion 30. As a result, the outer diameter of the cross-section of the upstream exhaust pipe 3 can be suppressed, improving the mountability of the exhaust purification device 1 on a vehicle.

[0093] (5) In addition, in the first to third embodiments, the downstream end of the upstream heat shield portion 50 of the upstream insulator 5 faces radially toward the inner pipe portion of the covering structure 10. Similarly, the upstream end of the downstream heat shield portion 60 of the downstream insulator 6 faces radially toward the inner pipe portion of the covering structure 10. As a result, the portion of the upstream exhaust pipe 3 that does not face the inner pipe portion and the portion of the downstream exhaust pipe 4 that does not face the inner pipe portion can be more reliably covered from the outer surface side by the upstream heat shield portion 50 or the downstream heat shield portion 60. Therefore, heat dissipation from the upstream exhaust pipe 3 and the downstream exhaust pipe 4 can be more effectively suppressed.

[0094] (6) Furthermore, in the upstream exhaust pipe 3 of the first and third embodiments, the main body portion 30 and the outlet portion 32 are integrally formed by, for example, press molding. Therefore, it is possible to suppress the formation of welds or the like at the boundary between the outlet portion 32 and the main body portion 30 of the upstream exhaust pipe 3 when these parts are joined, thereby suppressing the formation of steps on the inner surface of the upstream exhaust pipe 3. Consequently, it is possible to suppress the formation of deposits on the inner surface of the upstream exhaust pipe 3.

[0095] [8. Other Embodiments] (1) In the exhaust gas purification device 1 of the above embodiment, a curved section is provided in the exhaust pipe 2. However, the shape of the exhaust pipe is not limited to this, and for example, the exhaust pipe may be straight throughout. Even in such a case, the same effect can be obtained by providing a covering structure to the part of the exhaust pipe where each structure is provided.

[0096] (2) In the exhaust gas purification device 1 of the first and third embodiments, structures may be further provided on the outer circumferential surface of the outer pipe portion of the covering structure 10 between the upstream flange 35 and the upstream insulator 5, and between the downstream flange 43 and the downstream insulator 6. Also, in the exhaust gas purification device 1 of the second embodiment, structures may be further provided on the outer circumferential surface of the outer pipe portion of the covering structure 10 between the upstream flange 35 and the joining member 52, and between the downstream flange 43 and the downstream insulator 6. Furthermore, in the exhaust gas purification device 1 of the fourth embodiment, structures may be further provided on the outer circumferential surface of the portion of the outer pipe portion of the covering structure 10 facing the base portion 23C, in addition to the stay 21 and boss 22.

[0097] (3) Multiple functions of one component in the above embodiment may be realized by multiple components, or one function of one component may be realized by multiple components. Also, multiple functions of multiple components may be realized by one component, or one function realized by multiple components may be realized by one component. Furthermore, some of the configurations of the above embodiment may be omitted. Also, at least some of the configurations of the above embodiment may be added to or replaced with the configurations of other above embodiments. [Explanation of Symbols]

[0098] A...Axis, W...Full circumference weld, 1...Exhaust purification device, 10...Covered structure, 2...Exhaust pipe, 2A...Curved section, 2B...Straight section, 20...Mounting section, 21...Stay, 21A...Joint, 22...Boss, 22A...Hole, 23...Inner circumference, 23A...Joint, 23B...Reduced diameter section, 23C...Base section, 3...Upstream exhaust pipe, 30...Main body, 30A...Curved section, 30B...Straight section, 31...Mounting section, 32...Outlet section, 33...Reduced diameter section, 34...Upstream outer circumference, 35...Upstream flange, 4 ...downstream exhaust pipe, 40...inlet section, 41...tapered section, 42...housing section, 43...downstream flange, 44...purification member, 45...downstream outer circumference, 45A...joint, 5...upstream insulator, 50...upstream heat shield section, 50A...enlarged diameter section, 51...joint, 52...joint member, 52A...inner joint, 52B...outer joint, 6...downstream insulator, 60...downstream heat shield section, 60A...inclined section, 60B...straight section, 61...joint, 7...injector, 8...mixer.

Claims

1. An exhaust gas purification device configured to purify the exhaust gas of an internal combustion engine, An exhaust pipe that forms the exhaust flow path, A mounting portion provided in the exhaust pipe, which is a portion to which a device for supplying urea solution toward the exhaust flow path is attached, A purification member for purifying exhaust gas is provided downstream of the mounting portion in the exhaust gas flow path, A plurality of structures are provided between the mounting portion and the purification member on the outer surface of the exhaust pipe, The exhaust pipe is provided with a covering structure, The aforementioned covering structure is The outer tube portion is a tubular part that forms the outer surface of the exhaust pipe, It has an inner tube portion which is a tubular member that is positioned away from the outer tube portion and facing the inner circumferential surface of the outer tube portion, Each of the aforementioned structures is provided on the outer circumferential surface of the outer tube portion in the covering structure, The inner pipe section is arranged to face each of the aforementioned structures. Exhaust gas purification device.

2. An exhaust gas purification device according to claim 1, The exhaust pipe comprises an upstream exhaust pipe on which the mounting portion is provided, and a downstream exhaust pipe on which the purification member is arranged. The upstream flange, which is the structure, is provided at the downstream end of the upstream exhaust pipe. The downstream flange, which is the structure, is provided at the upstream end of the downstream exhaust pipe. The upstream exhaust pipe and the downstream exhaust pipe are connected via the upstream flange and the downstream flange, The inner pipe section is positioned to face the upstream flange and the downstream flange. Exhaust gas purification device.

3. An exhaust gas purification device according to claim 1 or claim 2, The upstream end of the inner pipe section is located upstream of each of the aforementioned structures, and the downstream end is located downstream of each of the aforementioned structures. Exhaust gas purification device.

4. An exhaust gas purification device according to claim 1 or claim 2, The cross-section of the inner pipe portion perpendicular to the direction of exhaust flow is smaller than the cross-section of the portion adjacent to the upstream side of the inner pipe portion in the exhaust pipe. Exhaust gas purification device.

5. An exhaust gas purification device according to claim 2, The upstream exhaust pipe is further provided with an upstream heat shield facing the outer surface with a gap between them, The upstream heat shield is positioned so that its downstream end faces the inner pipe. Exhaust gas purification device.

6. An exhaust gas purification device according to claim 2, The downstream exhaust pipe is further provided with a downstream heat shield facing the outer surface with a gap between them, The downstream heat shield is positioned so that its upstream end faces the inner pipe. Exhaust gas purification device.

7. An exhaust gas purification device according to claim 2, The upstream exhaust pipe has an outlet portion which includes the downstream end, and a main body portion which is adjacent to the upstream side of the outlet portion and is molded integrally with the outlet portion. The outlet portion forms the inner tube portion in the covering structure. Exhaust gas purification device.

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