Exhaust pipe structure of internal combustion engine

Abstract

To provide an exhaust pipe structure of an internal combustion engine capable of further shortening labor and time required for a design change of an exhaust passage, even when changed to a longer exhaust emission control device.SOLUTION: The exhaust gas pipe adapter includes a cylindrical main body portion (21) that seals an inflow side space including an inflow surface 32A of the exhaust gas purification device, and a tubular inflow port (22) provided on a cylindrical surface of the main body portion, a purification device central axis 30Z of the exhaust gas purification device and a main body portion central axis 21Z of the main body portion are substantially parallel to each other, and an inflow port central axis 22Z of the inflow port (22) is at a twisted position without intersecting the main body portion central axis. The inflow side of the exhaust gas purification device is inserted into the main body portion from a hole portion formed in one bottom surface side 21C of the cylindrical main body portion, and a predetermined-distance side 32A is provided from an inflow surface side 21D of the exhaust gas purification device to the other bottom surface side L1 of the main body portion.SELECTED DRAWING: Figure 5

Description

[Technical Field]

[0001] The present invention relates to an exhaust pipe structure for an internal combustion engine. [Background technology]

[0002] An exhaust gas purification device for an internal combustion engine is disposed adjacent to the internal combustion engine for the purpose of raising the temperature to an activation temperature in a short period of time.

[0003] For example, Patent Document 1 discloses an exhaust pipe structure for an internal combustion engine in which a cylindrical exhaust purification catalyst device extending vertically is disposed adjacent to the internal combustion engine. The exhaust purification catalyst device includes a substantially cylindrical case extending vertically, a substantially cylindrical exhaust purification catalyst portion housed in the upper part of the case, and a substantially cylindrical DPF (Diesel Particulate Filter) housed in the lower part of the case, with the exhaust purification catalyst portion and the DPF disposed in close proximity. The upper end of the case and the upper end of the exhaust purification catalyst portion are positioned at substantially the same location. A low, substantially conical exhaust pipe inlet portion with a large obtuse apex angle is connected to the upper end of the case, and a low, substantially conical inlet space is formed between the upper end surface of the exhaust purification catalyst portion and the inner wall of the exhaust pipe inlet portion. An exhaust pipe main body is connected to a position offset toward the outer periphery of the conical surface of the exhaust pipe inlet portion, and extends in a curved manner to guide exhaust gas from the internal combustion engine to the vicinity of the outer periphery of the inlet space. Furthermore, the exhaust inlet of the exhaust pipe main body is connected to and located close to the exhaust outlet of the turbocharger, which is connected to the exhaust manifold. With the above structure, the exhaust gas guided from the exhaust pipe main body to the exhaust pipe introduction part is made to swirl circumferentially along the outer periphery within the inflow space of the exhaust pipe introduction part, and flows into the exhaust purification catalyst part from the upper end surface of the exhaust purification catalyst part. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] International Publication No. 2016 / 194201 Summary of the Invention [Problem to be solved by the invention]

[0005] In recent years, in order to improve the purification rate of exhaust gases, it has become common to use longer exhaust purification catalyst sections and longer DPFs (because increasing the length has a greater effect on improving the purification rate than increasing the diameter).In the exhaust pipe structure of an internal combustion engine described in Patent Document 1, there is almost no distance from the upper end face of the exhaust purification catalyst section inside the case to the inner wall of the exhaust pipe introduction section, and there is also almost no distance from the lower end face of the exhaust purification catalyst section to the DPF, so when a longer exhaust purification catalyst section is used, it is necessary to extend the case upward or downward at least one way.

[0006] Extending the case upward requires a design change to the exhaust path so that it can be extended upward without interfering with surrounding equipment in an engine room packed with various devices, which not only requires a great deal of time and effort, but it may also not be possible to extend it upward. Even if it were possible to extend it upward, it may be necessary to change the design of the turbocharger position or the shape of the exhaust manifold in order to connect the exhaust inlet of the exhaust pipe main body to the exhaust outlet of a nearby turbocharger in a gently curved manner. Furthermore, even if the design of the exhaust path is changed to extend the case downward, the design change requires a great deal of time and effort, and it may also not be possible to extend it downward.

[0007] The present invention was devised in consideration of these points, and its objective is to provide an exhaust pipe structure for an internal combustion engine that can further reduce the effort and time required to change the design of the exhaust path, even when changing to a longer exhaust purification device. [Means for solving the problem]

[0008] To solve the above problems, a first invention provides an exhaust pipe structure for an internal combustion engine, comprising: an exhaust purification device provided in an exhaust path of the internal combustion engine; and an exhaust pipe adapter provided on the exhaust inflow side of the exhaust purification device and guiding the exhaust from the internal combustion engine to an inflow surface of the exhaust purification device. The exhaust pipe adapter has a cylindrical main body that seals an inflow space that is the inflow side space including the inflow surface of the exhaust purification device, and a cylindrical inlet provided in the cylindrical surface of the main body and guiding the exhaust from the internal combustion engine into the main body. A purification device central axis that is the central axis of the columnar exhaust purification device and a main body central axis that is the central axis of the main body are approximately parallel, and an inlet central axis that is the central axis of the inlet is skewed relative to the main body central axis without intersecting with it. The inlet side of the exhaust purification device is inserted into the main body through a hole formed in one of the bottom surfaces of the cylindrical main body, and a predetermined distance is left between the inlet surface of the exhaust purification device and the other bottom surface of the main body, which is an exhaust pipe structure for an internal combustion engine.

[0009] Next, the second invention is an exhaust pipe structure for an internal combustion engine according to the first invention, wherein the one bottom surface and the central axis of the inlet are approximately parallel, and when viewed from a direction perpendicular to both the central axis of the main body and the central axis of the inlet, the position of the inlet surface within the main body is within a range from the one bottom surface to a position near the central axis of the inlet, beyond the central axis of the inlet.

[0010] Next, the third invention is an exhaust pipe structure of an internal combustion engine according to the first or second invention, wherein the inlet side of the exhaust purification device protrudes from the one bottom surface into the main body portion, and a circumferential gap, which is a gap that is continuous in the circumferential direction, is formed between the inner wall side of the cylindrical surface of the main body portion and the outer wall side of the side surface of the exhaust purification device protruding into the main body portion.

[0011] Next, a fourth invention is an exhaust pipe structure of an internal combustion engine according to the third invention, wherein a guide plate is provided within the main body portion to guide at least a portion of the exhaust gas that flows into the main body portion from the inlet to the inlet surface of the exhaust purification device.

[0012] Next, the fifth invention is an exhaust pipe structure for an internal combustion engine according to the fourth invention, in which, when the space within the main body, as viewed from a direction perpendicular to both the central axis of the main body and the central axis of the inlet, is divided into one space, which is the space between a virtual extended inlet surface, which is a virtual extension of the inlet surface, and one bottom surface of the cylindrical main body, and another space, which is the space between the virtual extended inlet surface and the other bottom surface of the cylindrical main body, a guide plate having an inclined surface that guides at least a portion of the exhaust gas that flows from the inlet into the one space to the other space is provided within the main body between the inlet and the exhaust purification device.

[0013] Next, the sixth invention is an exhaust pipe structure for an internal combustion engine according to the fifth invention, in which, when the opening of the inlet is viewed from a direction parallel to the central axis of the inlet and from the side of the inlet, the central axis of the inlet is twisted relative to the central axis of the main body and is spaced apart to one side from the central axis of the main body, and the guide plate is positioned at a position biased to one side with respect to the opening and is provided to cover the circumferential gap on the one side. [Effects of the Invention]

[0014] According to the first aspect of the present invention, the columnar exhaust purification device is inserted through a hole in one bottom surface of the cylindrical main body, and a predetermined distance is provided between the inlet surface of the exhaust purification device and the other bottom surface of the main body. Therefore, when changing to a longer exhaust purification device, it is only necessary to insert the exhaust purification device so that the predetermined distance becomes shorter. Therefore, even when changing to a longer exhaust purification device, it is possible to further reduce the effort and time required to change the design of the exhaust path.

[0015] According to the second aspect of the present invention, it is possible to ensure an appropriate space for guiding the exhaust gas that has flowed in from the inlet to the inlet surface of the exhaust purification device.

[0016] In order to fit the exhaust purification device protruding into the main body without forming a circumferential gap between the outer wall of the side surface and the inner wall of the cylindrical surface of the main body, high dimensional accuracy is required, making manufacturing relatively difficult. However, according to the third invention, a circumferential gap is provided between the outer wall of the side surface of the exhaust purification device protruding into the main body and the inner wall of the cylindrical surface of the main body, so ordinary dimensional accuracy is sufficient and manufacturing is relatively easy.

[0017] According to the fourth aspect of the present invention, by providing the guide plate, the exhaust gas that has flowed into the circumferential gap can be appropriately guided to the inlet surface of the exhaust purification device.

[0018] According to the fifth aspect of the present invention, exhaust gas attempting to flow from the inlet into the circumferential gap can be efficiently guided to the inlet surface of the exhaust purification device.

[0019] According to the sixth invention, the diameter of the swirling flow of exhaust gas flowing into the main body can be prevented from increasing, and the flow velocity distribution of the exhaust gas flowing into the inlet surface of the exhaust purification device (exhaust flow velocity distribution in the direction of the central axis of the purification device at the inlet surface) can be made more uniform. [Brief explanation of the drawings]

[0020] [Figure 1] 1 is a diagram illustrating an exhaust path disposed adjacent to an internal combustion engine and having an exhaust pipe structure described in this embodiment. FIG. [Figure 2] FIG. 2 is a perspective view of a portion of the exhaust path shown in FIG. [Figure 3] FIG. 3 is an exploded perspective view of a portion of the exhaust path shown in FIG. 2. [Figure 4] 4 is a cross-sectional view (plan view) illustrating the positions of the exhaust purification device, the circumferential gap, and the guide plate in the exhaust pipe adapter. FIG. [Figure 5] 4 is a cross-sectional view (side view) illustrating the positions of the exhaust purification device, one space, the other space, and a guide plate in the exhaust pipe adapter. FIG. [Figure 6] FIG. 5 is a perspective view of the cross section shown in FIG. [Figure 7] 7 is a view of the exhaust pipe adapter in FIG. 2 as viewed from direction VII. [Figure 8] 10 is a perspective view illustrating the flow of exhaust gas that flows into the main body from the inlet when there is no guide plate. FIG. [Figure 9] 10 is a perspective view illustrating the flow of exhaust gas that flows into the main body from the inlet when a guide plate is provided. FIG. DETAILED DESCRIPTION OF THE INVENTION

[0021] <General structure of the exhaust passage 10 of the internal combustion engine 1 (FIGS. 1 and 2)> An exhaust pipe structure 2 (exhaust pipe structure of an internal combustion engine) having an exhaust pipe adapter 20 and an oxidation catalyst unit 30 (corresponding to an exhaust purification device) will be described below with reference to the drawings. First, an example of an exhaust path 10 of an internal combustion engine 1 will be described using Figure 1. The internal combustion engine 1 in the example of Figure 1 is a so-called diesel engine. The internal combustion engine 1 is mounted on a vehicle, and when up, down, front, rear, left, and right are written in the figure, they refer to the up, down, front, rear, left, and right directions of the vehicle in which the internal combustion engine 1 is mounted.

[0022] Fig. 1 shows an exhaust path 10 of an internal combustion engine 1, extending from an exhaust manifold 10A to an SCR unit (Selective Catalytic Reduction unit) 70 and an extension adapter 80. Fig. 2 shows a perspective view of the exhaust path 10 shown in Fig. 1, extending from an exhaust pipe adapter 20 to the SCR unit 70 and the extension adapter 80. The exhaust path 10 is disposed adjacent to the internal combustion engine 1 for the purpose of raising the temperatures of various catalysts and the like to their activation temperatures in a short period of time. The internal combustion engine 1 has a cylinder head 1A, a cylinder 1B, a crankcase 1C, an oil pan 1D, and the like.

[0023] As shown in Fig. 1, an exhaust path 10 includes, from upstream to downstream, an exhaust manifold 10A, a turbocharger turbine 10B, a turbine outlet pipe 10C, an exhaust pipe adapter 20, an oxidation catalyst unit 30 (corresponding to an exhaust purification device), a DPF adapter 40, a DPF unit 50, an SCR adapter 60, an SCR unit 70, an extension adapter 80, etc. In Fig. 1, the intake path includes an intake pipe 11A, a turbocharger compressor 11B, a compressor outlet pipe 11C, an intercooler and an intake manifold (not shown), etc., but a description of the intake path will be omitted. In addition, since the exhaust manifold 10A, the turbocharger turbine 10B, and the turbine outlet pipe 10C are almost all existing components, a detailed description of these components will be omitted.

[0024] An exhaust inlet of an exhaust manifold 10A is connected to an exhaust port provided in the cylinder head 1A. An exhaust inlet of a turbine 10B of a supercharger (turbo) is connected to an exhaust outlet of the exhaust manifold 10A. A turbine outlet pipe 10C having an exhaust outlet of the turbine 10B extends substantially horizontally and is connected to an inlet 22 of an exhaust pipe adapter 20.

[0025] As shown in FIG. 2, the exhaust pipe adapter 20 has a substantially cylindrical main body 21 and a substantially cylindrical inlet 22. As shown in FIG. 3, a hole 24 into which the inlet side of the oxidation catalyst unit 30 is inserted is formed in a main body base 21A of the main body 21. Furthermore, as shown in FIG. 1, a flange portion 22A of the inlet 22 is connected to the turbine outlet pipe 10C, and the main body 21 is connected to the inlet side of the oxidation catalyst unit 30. The exhaust pipe adapter 20 is provided on the exhaust inlet side of the oxidation catalyst unit 30 and guides the exhaust of the internal combustion engine 1 to the inlet surface of the oxidation catalyst unit 30. The exhaust pipe adapter 20 receives exhaust gas from a substantially horizontal direction and directs the exhaust gas to flow out in a substantially vertical direction (downward). As shown in FIG. 2, an inlet central axis 22Z, which is the central axis of the inlet 22, is substantially horizontal, and a main body central axis 21Z, which is the central axis of the main body 21, is substantially vertical.

[0026] As shown in FIG. 3, the oxidation catalyst unit 30 is integrated with a substantially cylindrical oxidation catalyst case 31 and a substantially columnar oxidation catalyst 32. The oxidation catalyst 32 is a catalyst that oxidizes and purifies HC (hydrocarbons) and CO (carbon monoxide) contained in the exhaust gas from the internal combustion engine 1. The inlet side, including the inlet surface 32A of the oxidation catalyst unit 30, is inserted into a hole 24 (see FIG. 3) of the exhaust pipe adapter 20 and fixed thereto by welding or the like. The outlet side, including the outlet surface 32B of the oxidation catalyst unit 30, is inserted into an exhaust gas inlet 40A (see FIG. 3) of the DPF adapter 40 and fixed thereto by welding or the like. If the axial length of the oxidation catalyst unit 30 is increased to improve purification efficiency or the like, at least one of the insertion length into the exhaust pipe adapter 20 and the insertion length into the DPF adapter 40 is increased. The oxidation catalyst unit 30 is arranged so that a purification device central axis 30Z (see FIGS. 2 and 3), which is the central axis, is in the substantially vertical direction.

[0027] 3, the DPF adapter 40 is a substantially L-shaped pipe having an exhaust gas inlet 40A into which the outlet side of the oxidation catalyst unit 30 is inserted, and an exhaust gas outlet 40B into which the inlet side of the DPF unit 50 is inserted. The DPF adapter 40 converts the exhaust gas flowing out from the outlet surface of the oxidation catalyst unit 30, which flows substantially vertically downward, into a substantially horizontal direction toward the inlet surface of the DPF unit 50.

[0028] As shown in FIG. 3, the DPF unit 50 is integrated with a substantially cylindrical DPF case 51 and a substantially columnar DPF (Diesel Particulate Filter) 52. The DPF 52 is a filter that captures fine particulate matter contained in the exhaust gas of the internal combustion engine 1. An inlet side of the DPF unit 50, including a DPF inlet surface 52A, is inserted into an exhaust outlet 40B (see FIG. 3) of the DPF adapter 40 and fixed thereto by welding or the like. An outlet side of the DPF unit 50, including a DPF outlet surface 52B, is inserted into an exhaust inlet of an SCR adapter 60 (see FIG. 2) and fixed thereto by welding or the like. If the axial length of the DPF unit 50 is increased to improve purification efficiency or the like, at least one of the insertion length into the DPF adapter 40 and the insertion length into the SCR adapter 60 is increased. The DPF unit 50 is disposed so that a DPF central axis 50Z is substantially horizontal.

[0029] As shown in FIG. 2, the SCR adapter 60 is a substantially cylindrical pipe having an exhaust inlet into which the outflow side of the DPF unit 50 is inserted, and an exhaust outlet into which the inflow side of the SCR unit 70 is inserted.

[0030] As shown in FIG. 2, the SCR unit 70 is integrated with a substantially cylindrical SCR case 71 and a substantially columnar SCR (Selective Catalytic Reduction) unit 72. The SCR unit 72 is a catalyst that reduces and purifies NOx (nitrogen oxides) contained in the exhaust gas from the internal combustion engine 1. The inlet side of the SCR unit 70, including an SCR inlet surface 72A, is inserted into an exhaust gas outlet of an SCR adapter 60 (see FIG. 2) and fixed thereto by welding or the like. The outlet side of the SCR unit 70, including an SCR outlet surface 72B, is inserted into an exhaust gas inlet of an extension adapter 80 (see FIG. 2) and fixed thereto by welding or the like. If the axial length of the SCR unit 70 is increased to improve purification efficiency or the like, at least one of the insertion length into the SCR adapter 60 and the insertion length into the extension adapter 80 is increased. The SCR unit 70 is disposed so that the SCR central axis is substantially horizontal.

[0031] The extension adapter 80 is a substantially cylindrical pipe as shown in FIG. 2, and has an exhaust inlet into which the outflow side of the SCR unit 70 is inserted, and extends toward a muffler (silencer) or the like (not shown).

[0032] <Details of the exhaust pipe structure 2 having the exhaust pipe adapter 20 and the oxidation catalyst unit 30 (corresponding to the exhaust purification device) (Figs. 2 to 7)> The exhaust pipe structure 2 of the present invention is an exhaust pipe structure having an oxidation catalyst unit 30 (corresponding to an exhaust purification device) and an exhaust pipe adapter 20. Fig. 3 is an exploded perspective view from the exhaust pipe adapter 20 to the DPF unit 50 in Fig. 2. The exhaust pipe adapter 20 has a main body 21 formed into a cylindrical shape by a main body base 21A and a main body cover 21B, and a substantially cylindrical inlet 22 provided on the cylindrical surface of the main body 21. A guide plate 23 is provided inside the main body 21.

[0033] Fig. 4 is a diagram (plan view) of a cross section of the main body 21 and inlet 22 of the exhaust pipe adapter 20 in Fig. 2 cut along an imaginary horizontal plane including the inlet central axis 22Z, as viewed from above. Fig. 5 is a diagram (side view) of a cross section of the exhaust pipe adapter 20 and the oxidation catalyst unit 30 in Fig. 2 cut along the imaginary cutting plane VM shown in Fig. 4, as viewed from the V direction shown in Fig. 4. Fig. 6 is a perspective view of Fig. 4, and Fig. 7 is a diagram of the exhaust pipe adapter 20 and the oxidation catalyst unit 30 in Fig. 2 as viewed from the VII direction.

[0034] 2, the exhaust pipe adapter 20 has a substantially cylindrical main body 21 and a substantially cylindrical inlet 22. The main body 21 seals an inlet space, which is a space on the inlet side of the oxidation catalyst unit 30 and includes an inlet surface 32A of the oxidation catalyst unit 30. The inlet 22 is provided on the cylindrical surface of the substantially cylindrical main body 21 and guides exhaust gas from the internal combustion engine 1 (see FIG. 1) into the main body 21.

[0035] As shown in Fig. 2, a purification apparatus central axis 30Z, which is the central axis of the substantially columnar oxidation catalyst unit 30, and a main body central axis 21Z, which is the central axis of the substantially cylindrical main body 21, extend in a substantially vertical direction, are substantially parallel to each other, and are substantially coaxial. Furthermore, an inlet central axis 22Z, which is the central axis of the substantially cylindrical inlet 22, extends in a substantially horizontal direction. As shown in Figs. 4, 6, and 7, the inlet central axis 22Z does not intersect with or is not parallel to the main body central axis 21Z, but is skewed relative to the main body central axis 21Z.

[0036] 3, the main body 21 is formed into a substantially cylindrical shape by welding or the like of a main body base 21A on the side closer to the oxidation catalyst unit 30 and a main body cover 21B on the side farther from the oxidation catalyst unit 30. A hole 24 (see FIG. 3) for inserting the oxidation catalyst unit 30 is formed in one bottom surface 21C (the bottom surface of the main body base 21A, see FIG. 5) of the substantially cylindrical main body 21.

[0037] The inflow side of the oxidation catalyst unit 30 is inserted into the main body 21 (see FIGS. 2 and 5) through a hole 24 (see FIG. 3) formed in one bottom surface 21C (see FIGS. 3 to 6). As shown in FIG. 5, a predetermined distance L1 is provided between the inflow surface 32A of the oxidation catalyst unit 30 and the other bottom surface 21D (the bottom surface of the main body cover 21B), which is the other bottom surface of the main body 21.

[0038] As shown in Fig. 5, the one bottom surface 21C and the inlet central axis 22Z are substantially parallel (substantially horizontal). As shown in Fig. 5, when viewed from a direction perpendicular to both the main body central axis 21Z and the inlet central axis 22Z, the position of the inlet surface 32A of the oxidation catalyst unit 30 within the main body 21 is preferably within a range W1 from the one bottom surface 21C to a position close to the inlet central axis 22Z, slightly beyond the inlet central axis 22Z. The inlet side of the oxidation catalyst unit 30 preferably protrudes from the one bottom surface 21C of the main body 21 into the main body 21. In the following explanation, an example will be given in which the inlet side of the oxidation catalyst unit 30 protrudes slightly above the inlet central axis 22Z, as shown in Fig. 5.

[0039] As shown in Figure 4, a circumferential gap 25, which is a gap that continues in the circumferential direction, is formed between the cylindrical inner wall side 21E of the main body portion 21 and the side outer wall side 30E of the oxidation catalyst unit 30 that protrudes into the main body portion 21.

[0040] 4 to 6, a guide plate 23 is provided within the main body 21 to guide at least a portion of the exhaust gas that has flowed into the main body 21 from the inlet 22 to the inlet surface 32A of the oxidation catalyst unit 30. For example, the guide plate 23 is fixed to one bottom surface 21C and the inner wall side of the side surface of the main body base 21A by welding or the like (see FIGS. 4 to 6).

[0041] 5, it is assumed that the space within the main body 21 is divided into one space 21J and another space 21K by an imaginary extended inlet surface VH, which is an imaginary extension of the inlet surface 32A, when viewed from a direction perpendicular to both the main body central axis 21Z and the inlet central axis 22Z. The one space 21J is the space between the one bottom surface 21C and the imaginary extended inlet surface VH, and the other space 21K is the space between the other bottom surface 21D and the imaginary extended inlet surface VH. As shown in FIG. 5, the lower end of the guide plate 23 is in contact with the one bottom surface 21C, and the upper end of the guide plate 23 extends to the inlet surface 32A of the oxidation catalyst unit 30 and is at approximately the same height as the inlet surface 32A.

[0042] 5 and 6, the guide plate 23 is provided in the main body 21 between the inlet 22 and the oxidation catalyst unit 30. As shown in Figures 5 and 6, the guide plate 23 has an inclined surface 23M that guides at least a portion of the exhaust gas that has flowed from the inlet 22 into the one space 21J (see Figure 5) to the other space 21K (see Figure 5).

[0043] 6 and 7, when opening 22C of inlet 22 is viewed in a direction parallel to inlet central axis 22Z (direction A in FIG. 6) and from the side of inlet 22, inlet central axis 22Z does not intersect with, nor is parallel to, main body central axis 21Z, but is in a twisted position and is spaced to one side (the left side of the paper in FIG. 7) from main body central axis 21Z. As shown in FIG. 7, guide plate 23 is disposed in a position biased to one side (the left side of the paper in FIG. 7) with respect to opening 22C.

[0044] The guide plate 23 is disposed at a position offset to one side with respect to the opening 22C. Therefore, as shown in FIG. 7, an edge 23A on one side of the guide plate 23 is not visible from the opening 22C, but an edge 23B on the other side of the guide plate 23 is visible from the opening 22C. That is, as shown in FIG. 7, the edge 23A on one side of the guide plate 23 is located to one side of the edge 22J on one side of the opening 22C, and the edge 23B on the other side of the guide plate 23 is located to one side of the edge 22K on the other side of the opening 22C. Therefore, the guide plate 23 is disposed at a position offset to one side with respect to the opening 22C. The guide plate 23 is disposed so as to cover the one-side circumferential gap 25A, which is the circumferential gap 25 on one side (the left side of the drawing in FIG. 7), but does not cover the other-side circumferential gap 25B, which is the circumferential gap 25 on the other side (the right side of the drawing in FIG. 7).

[0045] <Effects of the guide plate 23 (Fig. 8, Fig. 9)> Next, we will explain examples of the path that the exhaust gas flowing in from the inlet 22 takes to reach the inlet surface 32A in the exhaust pipe structure 2 having the above-described exhaust pipe adapter 20 and oxidation catalyst unit 30. Fig. 8 shows an example of the path of the exhaust gas flow when the guide plate 23 is not provided, and Fig. 9 shows an example of the path of the exhaust gas flow when the guide plate 23 is provided.

[0046] 8, which does not have the guide plate 23, exhaust gas G1A that flows into the exhaust pipe adapter 20 from the opening 22C of the inlet 22 becomes exhaust gas G2A that flows into the one-side circumferential gap 25A and becomes a swirling flow that flows within the circumferential gap 25. As the swirling flow of exhaust gas G3A approaches the inlet 22, it flows from the circumferential gap 25 in the one-side space 21J (see FIG. 5) to the other-side space 21K (see FIG. 5) and becomes exhaust gas G4A that swirls above the inlet surface 32A and heads toward the inlet surface 32A. In this case, the exhaust gas flows from the exhaust gas G2A flowing within the circumferential gap 25 to the exhaust gas G3A and then to the exhaust gas G4A that swirls above the inlet surface 32A, and the swirl radius R1A of the exhaust gas swirling above the inlet surface 32A immediately before flowing into the inlet surface 32A is relatively large. Therefore, the non-inflow area BA (area where the flow velocity of the exhaust gas in the direction of the purification device central axis 30Z is almost zero) into which the exhaust gas G4A does not flow is relatively large on the inflow surface 32A.

[0047] 9, which includes the guide plate 23, exhaust gas G1B that flows into the exhaust pipe adapter 20 from the opening 22C of the inlet 22 is prevented by the guide plate 23 from flowing into the one-side circumferential gap 25A and becomes exhaust gas G2B that flows along the guide plate 23. The exhaust gas G2B then becomes exhaust gas G3B that flows toward the inlet surface 32A and becomes a swirling flow that swirls above the inlet surface 32A. The swirl diameter R1B of the swirling flow at this time is smaller than the swirl diameter R1A of the circumferential gap 25 shown in FIG. 8. Therefore, a non-inlet region BB (a region where the flow velocity of the exhaust gas in the direction of the purification device central axis 30Z is almost zero) on the inlet surface 32A into which the exhaust gas G4B does not flow is much smaller than the non-inlet region BA shown in FIG. 8.

[0048] Therefore, the guide plate 23 can make the flow velocity distribution of the exhaust gas parallel to the purification device central axis 30Z on the inflow surface 32A of the oxidation catalyst unit 30 more uniform, thereby further improving the purification rate of the oxidation catalyst unit 30.

[0049] <Effects of Exhaust Pipe Structure 2, etc.> As described above, in the exhaust pipe structure 2 described in this embodiment, even if the oxidation catalyst unit 30 (corresponding to an exhaust purification device) is changed to a longer oxidation catalyst unit for the purpose of improving the purification rate, for example, during the development of a vehicle, it is only necessary to adjust the protruding length into the exhaust pipe adapter 20. Therefore, even when changing to a longer oxidation catalyst unit (corresponding to an exhaust purification device), it is possible to further reduce the effort and time required for the design change.

[0050] <Other> The exhaust pipe structure 2 for an internal combustion engine of the present invention is not limited to the configuration, structure, appearance, shape, etc. described in this embodiment, and various modifications, additions, and deletions are possible within the scope of the present invention. For example, the guide plate 23 may be omitted.

[0051] In the description of this embodiment, the oxidation catalyst unit 30 has been described as an exhaust purification device, but the exhaust purification device is not limited to the oxidation catalyst unit 30, and may be a DPF unit 50, an SCR unit 70, or in the case of a gasoline engine, a three-way catalyst unit (not shown) having a three-way catalyst.

[0052] In the description of this embodiment, an example has been described in which a turbocharger is used as a supercharger, but the supercharger is not limited to a turbocharger, and may be a supercharger, or the engine may not have a supercharger.

[0053] The exhaust pipe structure 2 for an internal combustion engine of the present invention is not limited to exhaust pipes for vehicles equipped with diesel engines, and can be applied to exhaust pipes for various devices equipped with diesel engines. Furthermore, the present invention is not limited to diesel engines, and can be applied to exhaust pipes for various engines such as gasoline engines, gas engines fueled by natural gas or the like, hydrogen engines fueled by hydrogen, and engines fueled by biofuels or a mixture of biofuels and diesel, as well as exhaust pipes for various devices equipped with these various engines. [Explanation of symbols]

[0054] 1. Internal combustion engine 2 Exhaust pipe structure 10 Exhaust path 10A Exhaust manifold 10B Turbine 10C Turbine Outlet Pipe 20 Exhaust pipe adapter 21 Main body 21A Main unit base 21B Body cover 21C Bottom side 21D Other bottom surface 21E Cylindrical inner wall side 21J One side space 21K Other space 21Z Center axis of main body 22 Inlet 22C opening 22Z Inlet center axis 23 Signboard 23M slope 24 Hole 25 Circumferential clearance 30 Oxidation catalyst unit (exhaust gas purification device) 30E Side outer wall 30Z Purification device central axis 31 Oxidation catalyst case 32 Oxidation catalyst 32A Inflow surface 32B Outflow surface 40 DPF adapter 40A Exhaust Inlet 40B Exhaust outlet 50 DPF unit 50Z DPF center axis 51 DPF case 52 DPF 52A DPF inflow surface 52B DPF outflow surface 60 SCR adapter 70 SCR unit 71 SCR case 72 SCR 72A SCR inflow surface 72B SCR outflow surface 80 Extension Adapter L1 Predetermined distance VH Virtual extended inlet surface VM Virtual Cutting Plane

Claims

1. An exhaust pipe structure for an internal combustion engine, comprising: an exhaust purification device provided in an exhaust path of the internal combustion engine; and an exhaust pipe adapter provided on an exhaust inflow side of the exhaust purification device and guiding exhaust gas from the internal combustion engine to an inflow surface of the exhaust purification device, The exhaust pipe adapter is a cylindrical main body portion that seals an inlet-side space that is a space on the inlet side including the inlet surface of the exhaust purification device; a cylindrical inlet provided on a cylindrical surface of the main body portion to guide exhaust gas from the internal combustion engine into the main body portion; and a purification device central axis that is a central axis of the columnar exhaust purification device and a main body central axis that is a central axis of the main body are substantially parallel to each other, The central axis of the inlet is skewed relative to the central axis of the main body without intersecting with the central axis of the inlet, the inlet side of the exhaust gas purification device is inserted into the cylindrical main body through a hole formed in one bottom surface of the main body, a predetermined distance is provided between the inlet surface of the exhaust gas purification device and the other bottom surface of the main body portion; Exhaust pipe structure of an internal combustion engine.

2. 2. An exhaust pipe structure for an internal combustion engine according to claim 1, The one bottom surface and the central axis of the inlet are substantially parallel to each other, When viewed from a direction perpendicular to both the main body central axis and the inlet central axis, the position of the inlet surface within the main body is within a range from the one bottom surface to a vicinity of the inlet central axis beyond the inlet central axis. Exhaust pipe structure of an internal combustion engine.

3. 3. An exhaust pipe structure for an internal combustion engine according to claim 1 or 2, the inlet side of the exhaust purification device protrudes from the one bottom surface into the main body portion, a circumferential gap that is a gap that continues in the circumferential direction is formed between an inner wall side of a cylindrical surface of the main body portion and an outer wall side of a side surface of the exhaust purification device that protrudes into the main body portion; Exhaust pipe structure of an internal combustion engine.

4. 4. An exhaust pipe structure for an internal combustion engine according to claim 3, a guide plate provided within the main body portion to guide at least a portion of the exhaust gas that has flowed into the main body portion from the inlet to the inlet surface of the exhaust purification device; Exhaust pipe structure of an internal combustion engine.

5. 5. An exhaust pipe structure for an internal combustion engine according to claim 4, The space within the main body portion as viewed from a direction perpendicular to both the main body portion central axis and the inlet central axis is a one-side space that is a space between a virtual extended inflow surface obtained by virtually extending the inflow surface and the one-side bottom surface of the cylindrical main body portion; and a second space which is a space between the virtual extended inflow surface and the second bottom surface of the cylindrical main body portion. Within the main body portion, between the inlet and the exhaust purification device, The guide plate has an inclined surface that guides at least a portion of the exhaust gas that has flowed into the one space from the inlet to the other space. Exhaust pipe structure of an internal combustion engine.

6. 6. An exhaust pipe structure for an internal combustion engine according to claim 5, When the opening of the inlet is viewed from a direction parallel to the central axis of the inlet and from the side of the inlet, the central axis of the inlet is in a twisted position with respect to the central axis of the main body and is spaced apart from the central axis of the main body to one side, and the guide plate is disposed at a position offset to the one side with respect to the opening and is provided to cover the circumferential gap on the one side. Exhaust pipe structure of an internal combustion engine.

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