exhaust duct

Abstract

The present invention provides an exhaust duct having a protrusion that suppresses heat from gas and provides high heat resistance reliability. The exhaust duct comprises: an exhaust pipe; and a protrusion continuously provided over a portion of the circumference of the inner surface of the exhaust pipe, inclined in the direction in which the exhaust pipe extends, with a cross-sectional area decreasing toward the downstream side of the exhaust pipe; and a convex portion on the inner surface of the protrusion.

Description

Technical Field

[0001] The invention relates to a structure of an exhaust passage. Background Art

[0002] The exhaust pipe of the internal combustion engine is provided with a sensor for detecting the oxygen concentration in the exhaust gas, etc. In the operation control of the internal combustion engine, for example, the intake air amount and the fuel injection amount are adjusted according to the detected oxygen concentration to control the air-fuel ratio.

[0003] Exhaust gas from each cylinder flows into a single exhaust pipe via an exhaust manifold. The exhaust gas flow has a high degree of directivity toward the downstream direction and is prone to deflection within the exhaust pipe cross section. Therefore, a mechanism for stirring the exhaust gas until it reaches the sensor is under investigation.

[0004] Japanese Patent Application Laid-Open No. 2016-142145 discloses a specific exhaust pipe having an outer protrusion and an inner protrusion as a method of forming uniform exhaust gas while cooling the flowing exhaust gas.

[0005] Japanese Patent Application Laid-Open No. 2018-193955 discloses a method of providing a convex guide portion upstream of the exhaust gas sensor as a method of making the exhaust gas from each cylinder contact the exhaust gas sensor without bias.

[0006] Japanese Patent Application Laid-Open No. 2014-126009 discloses providing a protrusion having a hole between a first exhaust pipe and a second exhaust pipe. Japanese Patent Application Laid-Open No. 2014-126009 describes that exhaust gas becomes turbulent when passing near the protrusion, causing the exhaust gas to diffuse. Summary of the Invention

[0007] The gas flowing through the exhaust pipe may reach a temperature exceeding 800° C. When the high-temperature gas flows through the exhaust pipe having the protrusion in Japanese Patent Application Laid-Open No. 2014-126009, as shown in FIG. Figure 9 As shown in the example of , in the protrusion, the closer to the front end, the more difficult it is to dissipate heat and the higher the temperature becomes. At this time, the temperature difference between the root and the front end of the protrusion becomes larger, as shown in FIG. Figure 10 As shown, a portion of the protrusion is subjected to large thermal stress, which may result in deformation or fracture of the protrusion.

[0008] The present invention has been made to solve the above-mentioned problem, and an object of the present invention is to provide an exhaust duct having a protrusion portion that suppresses heat from gas and has high heat-resistant reliability.

[0009] The exhaust passage of the present invention has:

[0010] exhaust pipe;

[0011] The protrusion is continuously provided on the inner surface of the exhaust pipe over a portion of the circumferential direction and is inclined in the extending direction of the exhaust pipe, with the cross-sectional area becoming smaller as it approaches the downstream side of the exhaust pipe.

[0012] The inner surface of the protrusion has a convex portion.

[0013] In one embodiment of the exhaust passage,

[0014] The convex portion is a linear convex portion,

[0015] The protrusions are provided at intervals in the extending direction.

[0016] In one embodiment of the exhaust passage,

[0017] The convex portion is provided at a portion of the protruding portion that is subjected to thermal stress.

[0018] In one embodiment of the exhaust passage,

[0019] The protrusions are arranged in a staggered shape.

[0020] According to the present invention, there is provided an exhaust duct having a protrusion portion that suppresses heat from gas and has high heat-resistant reliability.

[0021] The above and other objects, features and advantages of the present invention will become more fully understood from the detailed description set forth below and the accompanying drawings which are shown by way of illustration only and therefore should not be considered to limit the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 This is a schematic diagram showing an example of an exhaust duct according to the present invention.

[0023] Figure 2 It is a schematic perspective view showing an example of a protruding portion.

[0024] Figure 3 This is a schematic diagram for explaining the flow of gas.

[0025] Figure 4 These are a schematic plan view and a side view showing an example of a protruding portion of the exhaust duct according to the first embodiment.

[0026] Figure 5 It is a schematic diagram for explaining the flow of gas in the first embodiment.

[0027] Figure 6 It is a schematic bottom view showing an example of a protruding portion of the exhaust duct according to the second embodiment.

[0028] Figure 7 yes Figure 6AA cross-section diagram.

[0029] Figure 8 It is a schematic plan view and a side view showing an example of a protruding portion of an exhaust duct according to a third embodiment.

[0030] Figure 9 Graph showing the temperature of a protrusion in the related art.

[0031] Figure 10 This is a diagram showing the magnitude of thermal stress to which a protrusion in the related art is subjected. DETAILED DESCRIPTION

[0032] The present invention is described below based on embodiments. However, the invention within the scope of the claims is not limited to the following embodiments. Furthermore, for clarity, the following description and drawings are appropriately simplified. In this specification, the downstream direction in the axial direction (extension direction) of the exhaust pipe is defined as the X-axis, and the plane perpendicular to the X-axis is defined as the YZ plane (also referred to as a cross section).

[0033] Figure 1 The exhaust passage 10 shown in the example is an exhaust passage suitable for an internal combustion engine, and includes an exhaust pipe 11 ( 11A, 11B), a protruding portion 20 , and a convex portion 21 on the inner surface of the protruding portion 20 .

[0034] like Figure 2 As shown, the protrusion 20 is inclined toward the central axis of the exhaust pipe and has a tapered shape from the base end 23 of the protrusion 20 to the front end 22. The base end 23 of the protrusion is connected to the exhaust pipe 11A. The protrusion 20 and the exhaust pipe 11A can also be connected by welding or formed as one piece. Figure 2 The convex portion 21 is omitted.

[0035] exist Figure 1 In the embodiment, the exhaust pipe 11A may be connected to another pipe (not shown) on the upstream side. In addition, an air-fuel ratio sensor (not shown) is arranged on the downstream side of the exhaust pipe 11B.

[0036] exist Figure 1, the gas 31 flows in the X-axis direction. Here, in the exhaust path having the protrusion 20, a portion of the exhaust gas (32) contacts the protrusion 20 and flows along the protrusion 20 (33). Since the protrusion 20 is conical, as it moves downstream, a portion of the gas 34 detaches from the protrusion, generating an airflow shown by the dotted arrow. This airflow is continuously generated in the entire area of the protrusion 20 and becomes a vortex flow. After passing through the protrusion 20, the gas is also stirred in the entire tube. As a result, the surface uniformity of the gas is improved, and the measurement accuracy based on the sensor is improved. In addition, with respect to the exhaust passage of this embodiment, the opening portion in the protrusion 20 is also relatively large, and since the above-mentioned vortex flow diffuses in the entire tube, the increase in pressure loss can be suppressed.

[0037] The exhaust gas 31 may reach a high temperature exceeding 800° C., for example. Figure 9 The figure shows the temperature of the protrusion 51 when a gas at 800°C flows into the protrusion 51 without the convex portion 21. The base end 53 is close to the exhaust pipe 11 and is easy to dissipate heat, while the front end 52 cannot dissipate heat. Therefore, the front end 52 becomes hotter than the base end 53, and a large temperature gradient is generated between the front end 52 and the base end 53. As a result, Figure 10 As shown, thermal stress is generated, and a maximum thermal stress portion 54 is generated near the base end 53, which causes thermal deformation and thermal creep fracture.

[0038] The exhaust duct of the present invention solves the above problem by providing a convex portion 21 on the inner surface of the protrusion 20. Figure 3 As shown in the example, gas 35 has high straightness and therefore does not flow as indicated by dashed arrow 36, but instead flows straight toward the central axis of the exhaust pipe through protrusion 21. Consequently, within protrusion 20 having protrusion 21, a portion is created that is difficult for high-temperature gas to enter, forming a boundary insulation layer 40. As a result, contact between the high-temperature gas and the base material of protrusion 20 is suppressed. As described above, the exhaust duct of the present invention has a protrusion that suppresses heat from the gas and provides high heat resistance reliability.

[0039] Hereinafter, preferred embodiments will be described.

[0040] <First embodiment>

[0041] Reference Figure 4 The exhaust duct 10 of the first embodiment includes an exhaust pipe 11 and a protrusion 20. The protrusion 20 includes convex portions 21 on its inner surface. The convex portions 21 are linear convex portions (21A, 21B, 21C) and are spaced apart in the extending direction.

[0042] like Figure 5As shown, by providing a plurality of protrusions 21 , the gas flow 35 advances straighter toward the central axis side than the apex of the protrusion, further suppressing the heat received by the protrusion.

[0043] The spacing L between the plurality of protrusions 21 may be fixed or may vary. From the perspective of preventing gas from directly contacting the substrate of the protrusion 20, the protrusion spacing L is preferably 10 mm or less. On the other hand, the lower limit of the protrusion spacing L is not particularly limited, but is, for example, 1 mm or more.

[0044] Furthermore, from the perspective of suppressing the shedding of the boundary insulation layer due to the Karman vortex, the height H of the protrusion 21 is preferably 2 mm or greater. Suppressing the shedding of the boundary insulation layer due to the Karman vortex stabilizes the boundary insulation layer 40. The upper limit of the height H of the protrusion 21 is not particularly limited, but as an example, it is 10 mm or less.

[0045] The method for forming the linear protrusions is not particularly limited, and they can be easily formed by, for example, welding or the like.

[0046] <Second embodiment>

[0047] Reference Figure 6 The exhaust duct 10 of the second embodiment includes an exhaust pipe 11 and a protrusion 20. The protrusion 20 includes a convex portion 21 on its inner surface. The convex portion 21 is provided at a portion of the protrusion that is subjected to thermal stress.

[0048] like Figure 7 As shown, by providing the protrusion 21 at the portion where thermal stress is applied, it is possible to suppress the high-temperature gas 36 from coming into contact with the (maximum) thermal stress portion 54 .

[0049] The method for forming the convex portion of the second embodiment is not particularly limited, and the convex portion can be easily formed by, for example, bending or the like.

[0050] <Third embodiment>

[0051] Reference Figure 8 The exhaust duct 10 of the third embodiment includes an exhaust pipe 11 and a protrusion 20 . The protrusion 20 has convex portions 21D to 21I on its inner surface. The convex portions are arranged in a staggered pattern.

[0052] By arranging the protrusions in a staggered pattern, for example, as in protrusions 21D and 21H, a plurality of protrusions are arranged in the gas flow direction 37. By arranging a plurality of protrusions in the gas flow direction as in protrusions 21D and 21H, the gas flows straighter toward the central axis than the apex of the protrusions, similarly to the first embodiment, thereby suppressing heat exposure to the protrusions.

[0053] The convex portion interval L in the airflow direction (for example, the interval between the convex portion 21D and the convex portion 21H) is preferably 10 mm or less. On the other hand, the lower limit of the convex portion interval L is not particularly limited, but is 1 mm or more as an example.

[0054] Furthermore, to prevent shedding of the boundary insulation layer due to Karman vortices, the height H of the protrusion 21 is preferably 2 mm or greater. By preventing shedding of the boundary insulation layer due to Karman vortices, the boundary insulation layer is stabilized. The upper limit of the height H of the protrusion 21 is not particularly limited, but is, for example, 10 mm or less.

[0055] The method for forming the staggered convex portions is not particularly limited, and they can be formed, for example, by punching the base material so that a portion of the base end side remains, and then bending the base material.

[0056] As described above, the exhaust ducts of the first to third embodiments all exhibit a high stirring effect while suppressing pressure loss. Furthermore, they include protrusions that suppress heat from the gas and provide high heat resistance and reliability. Therefore, the exhaust ducts of the present invention are suitable for use, for example, in the exhaust ducts of internal combustion engines. Furthermore, the protrusions used in these embodiments are a relatively simple, single-piece structure, resulting in high reliability and reduced manufacturing costs.

[0057] From the above description, it is obvious that the embodiments of the present invention can be modified in many ways. These changes should not be considered as departing from the spirit and scope of the present invention, and it is obvious to those skilled in the art that these modifications are all included in the scope of the claims.

Claims

1. An exhaust channel having: exhaust pipe; The protrusion is continuously provided on the inner surface of the exhaust pipe over a portion of the circumferential direction and is inclined in the extending direction of the exhaust pipe, with the cross-sectional area becoming smaller as it approaches the downstream side of the exhaust pipe. The inner surface of the protrusion has a convex portion.

2. The exhaust passage according to claim 1, wherein The convex portion is a linear convex portion, The protrusions are provided at intervals in the extending direction.

3. The exhaust passage according to claim 1, wherein The convex portion is provided at a portion of the protruding portion that is subjected to thermal stress.

4. The exhaust passage according to claim 1, wherein The protrusions are arranged in a staggered shape.

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