Exhaust pipe structure

Abstract

To provide an exhaust pipe structure capable of enhancing dispersibility of a reducing agent in exhaust gas while suppressing an increase in pressure loss.SOLUTION: An exhaust pipe structure 1 is a structure to be connected to an internal combustion engine of a vehicle, and includes: an exhaust pipe 10 for letting exhaust gas G flow therein; an injector 50 for introducing a reducing agent K into the exhaust pipe 10; a dispersion plate 25 disposed at a confluence position of the gas G and the reducing agent K or downstream thereof to disperse the reducing agent K in the exhaust gas G; a mixer 26 disposed downstream of the dispersion plate 25 for mixing the reducing agent K in the exhaust gas G; and a tubular member 27 for holding the dispersion plate 25 and the mixer 26. The tubular member 27 has a spacer portion 27a for separating the dispersion plate 25 from the mixer 26 at a predetermined interval.SELECTED DRAWING: Figure 3

Description

Technical Field

[0001] The present disclosure relates to an exhaust pipe structure.

Background Art

[0002] As a conventional exhaust pipe structure, for example, there is an exhaust gas purification device described in Patent Document 1. This conventional exhaust gas purification device includes a diffusion member provided on the upstream side of the diffuser passage in the exhaust gas flow path and configured to cause the exhaust gas flowing in from the upstream side to flow out so as to diffuse into the diffuser passage, and a supply device configured to supply a reducing agent to a position upstream of the diffusion member in the exhaust gas flow path. Further, at a confluence position where the reducing agent merges with the exhaust gas, a guiding member is provided to branch the flow of the reducing agent into a plurality and guide it to the diffusion member.

[0003] Further, for example, an exhaust purification device described in Patent Document 2 includes an injector having a cylindrical injector body provided in an exhaust pipe. The injector body is inserted into the exhaust pipe. A nozzle attachment portion for attaching a nozzle for ejecting a reducing agent is provided at one end of the injector body, and control vanes for diffusing the ejected reducing agent are provided at the other end.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0005] Although the diffusion member in the exhaust gas purification device described in Patent Document 1 has a function of suppressing the deviation of the flow of exhaust gas in the diffusion flow path, it is considered not to have a function of dispersing the reducing agent that is unevenly present in the exhaust gas. In particular, when the supply direction of the reducing agent and the flow direction of the exhaust gas are different at the position where the exhaust gas and the reducing agent merge, the flow of the reducing agent is likely to deviate due to the influence of the flow of the exhaust gas.

[0006] In the exhaust gas purification device described in Patent Document 2, an intake opening for taking in exhaust gas is provided on the side wall of the injector body inserted into the exhaust pipe. The reducing agent introduced into the injector body collides with the baffle plate in the injector body together with the exhaust gas taken into the injector body from the intake opening and is dispersed in the exhaust gas. However, in the configuration of Patent Document 2, there is a concern that the pressure loss of the exhaust gas near the intake opening increases, which may affect the performance of the internal combustion engine.

[0007] The present disclosure has been made to solve the above problems, and an object thereof is to provide an exhaust pipe structure capable of enhancing the dispersibility of a reducing agent with respect to exhaust gas while suppressing an increase in pressure loss.

Means for Solving the Problems

[0008] An exhaust pipe structure according to one aspect of the present disclosure is an exhaust pipe structure connected to an internal combustion engine of a vehicle, including an exhaust pipe through which exhaust gas flows, an injector for introducing a reducing agent into the exhaust pipe, a dispersion plate disposed at a merging position of the exhaust gas and the reducing agent or on the downstream side thereof for dispersing the reducing agent in the exhaust gas, a mixer disposed on the downstream side of the dispersion plate for mixing the reducing agent in the exhaust gas, and a cylindrical member for holding the dispersion plate and the mixer, wherein the cylindrical member has a spacer portion for separating the dispersion plate and the mixer at a predetermined interval.

[0009] In this exhaust pipe structure, in the cylindrical member that holds the dispersion plate and the mixer, a spacer portion is provided that separates the dispersion plate and the mixer by a predetermined distance. By separating the dispersion plate and the mixer, the mixing of the reducing agent in the exhaust gas by the mixer can proceed with the reducing agent sufficiently dispersed in the exhaust gas by the dispersion plate, and it is possible to suppress the reducing agent from passing through both the dispersion plate and the mixer. Therefore, the dispersibility of the reducing agent with respect to the exhaust gas can be enhanced. Further, in this exhaust pipe structure, due to the presence of the spacer portion between the dispersion plate and the mixer, the main flow that has become narrow at the confluence position of the exhaust gas and the reducing agent will flow toward the mixer in a state where it has spread to some extent. Therefore, the retention of the main flow in the vicinity of the mixer can be suppressed, and an increase in pressure loss can be suppressed.

[0010] The spacer portion may have a length such that the reducing agent that has passed through the dispersion plate can collide with the spacer portion at least once. Thereby, the mixing of the reducing agent in the exhaust gas by the mixer can proceed with the reducing agent more reliably dispersed in the exhaust gas. Therefore, it becomes possible to further enhance the dispersibility of the reducing agent with respect to the exhaust gas.

[0011] The cylindrical member may be joined to the exhaust pipe via a bracket. Thereby, the dispersion plate and the mixer can be firmly held inside the exhaust pipe. Further, the heat retention effect of the exhaust gas by the cylindrical member is enhanced by the bracket, and the evaporation of the reducing agent can be promoted.

[0012] A gap portion through which the exhaust gas can flow may be provided between the bracket and the exhaust pipe. In this case, since a part of the high-temperature exhaust gas flows through the gap portion, the heat retention effect of the exhaust gas by the cylindrical member is further enhanced. Therefore, the evaporation of the reducing agent can be promoted more effectively.

Advantages of the Invention

[0013] According to the present disclosure, it is possible to enhance the dispersibility of the reducing agent with respect to the exhaust gas while suppressing an increase in pressure loss.

Brief Description of the Drawings

[0014]

Figure 1

Figure 2

Figure 3

Embodiments for Carrying Out the Invention

[0015] Hereinafter, with reference to the drawings, a preferred embodiment of the exhaust pipe structure according to one aspect of the present disclosure will be described in detail. Hereinafter, for convenience of explanation, the terms “upper” and “lower” are used based on the mounting state of the exhaust pipe on the vehicle. Also, the terms “upstream” and “downstream” are used based on the flow direction of the exhaust gas in the exhaust pipe.

[0016] FIG. 1 is a side view showing the upstream side of the exhaust pipe structure according to an embodiment of the present disclosure. Further, FIG. 2 is an enlarged perspective view showing the vicinity of the main part of the exhaust pipe structure shown in FIG. 1. As shown in FIGS. 1 and 2, the exhaust pipe structure 1 is a structure in which the exhaust pipe 10 is insulated by the first heat insulator 20 and the second heat insulator 30. The exhaust pipe 10 is made of a metal material such as stainless steel, for example. The exhaust pipe 10 has an overhanging region 19 that protrudes vertically downward due to the bending or bulging of the exhaust pipe 10. The first heat insulator 20 is disposed so as to cover the exhaust pipe 10 on the upstream side of the overhanging region 19. The second heat insulator 30 is disposed so as to cover the exhaust pipe 10 on the downstream side of the overhanging region 19.

[0017] The exhaust pipe 10 is connected to an internal combustion engine mounted on a vehicle and constitutes an exhaust passage for discharging exhaust gas generated by combustion in the combustion chamber of the internal combustion engine. The exhaust pipe 10 extends along the longitudinal direction of the vehicle, for example, in a state of being connected to the internal combustion engine. An example of the internal combustion engine is a diesel engine. Examples of vehicles to which the exhaust pipe structure 1 is applied include passenger cars, pickup trucks, buses, dumps, and the like.

[0018] Upstream of the exhaust pipe 10, for example, a turbocharger, a DOC (Diesel Oxidation Catalyst), a DPF (Diesel Particulate Filter), etc. are provided. Downstream of the exhaust pipe 10, for example, an SCR (Selective Catalytic Reduction) is provided. In the examples of FIGS. 1 and 2, an injector 50 for injecting a reducing agent (for example, aqueous urea) into the SCR is arranged in the exhaust pipe 10. The injector 50 is attached to the wall of the exhaust pipe 10 so as to face the below flow side of the exhaust pipe 10.

[0019] As shown in FIG. 1, an upstream side of the exhaust pipe 10 is provided with a connection part 11 and bending parts 12, 13, 14. Another exhaust pipe arranged on the upstream side (the internal combustion engine side) of the exhaust pipe 10 is connected to the connection part 11. A straight part 15 extending from the connection part 11 is inclined downward toward the injector 50 in accordance with the piping path of the upstream exhaust pipe. The bending part 12 bends the exhaust pipe 10 so that the downward inclination of a straight part 16 extending downstream of the bending part 12 is smaller than the downward inclination of the straight part 15. The extending direction of the straight part 15 downstream of the bending part 12 is along the direction of the injector 50 rather than the straight part 15.

[0020] The bending part 13 is provided near the base end part of the injector 50. The bending part 13 bends the exhaust pipe 10 so that the downward inclination of a straight part 17 downstream of the bending part 13 is larger than the downward inclination of the straight part 16. The straight part 17 downstream of the bending part 13 extends downward toward the mounting position of the injector 50. The bending part 14 bends the exhaust pipe 10 immediately downstream of the bending part 13 so that a straight part 18 downstream of the injector 50 extends generally along the axial direction of the injector 50. The straight part 18 downstream of the injector 50 extends in a state slightly inclined upward with respect to the horizontal plane.

[0021] Due to these bent portions 12, 13, and 14, the piping path of the exhaust pipe 10 is a path that can avoid interference with, for example, the lower structure of the vehicle (such as the cross member of the suspension). Also, an injector 50 attached to inject the reducing agent toward the rear of the vehicle enables the injection of the reducing agent downstream inside the exhaust pipe 10.

[0022] The exhaust pipe 10 has an overhanging region 19 that protrudes due to the bending of the bent portion 14. That is, in the exhaust pipe 10, a certain range on the downstream side of the bent portion 14 is the overhanging region 19 formed by the bending of the bent portion 14. The overhanging region 19 is, as an example, a region including the point located most vertically downward (the point with the minimum ground clearance) in the exhaust passage including the exhaust pipe 10.

[0023] As shown in FIG. 2, the first heat insulator 20 has a pair of heat shield plates 21 and 22 provided along the outer surface of the exhaust pipe 10 on the upstream side of the overhanging region 19. The second heat insulator 30 has a pair of heat shield plates 31 and 32 provided along the outer surface of the exhaust pipe 10 on the downstream side of the overhanging region 19. The first heat insulator 20 has a left - right divided structure by the heat shield plates 21 and 22 when viewed from the axial direction of the exhaust pipe 10. Similarly, the second heat insulator 30 has a left - right divided structure by the heat shield plates 31 and 32 when viewed from the axial direction of the exhaust pipe 10.

[0024] The downstream end 20a of the first heat insulator 20 and the upstream end 30a of the second heat insulator 30 have an overlapping portion R so that a gap portion is formed along the circumferential direction of the exhaust pipe 10 and communicates with the outside. In the present embodiment, the upstream end 30a of the second heat insulator 30 has an increased diameter in the overlapping portion R and is arranged outside the exhaust pipe 10 in the radial direction with respect to the downstream end 20a of the first heat insulator 20. A wire mesh 40 is arranged in the gap portion. The wire mesh 40 is formed of, for example, stainless steel or the like. The wire mesh 40 allows a liquid such as water to pass through while capturing foreign substances such as withered grass.

[0025] FIG. 3 is a cross-sectional view showing the vicinity of the main part of the exhaust pipe structure shown in FIG. 1. As shown in the figure, in the exhaust pipe 10, corresponding to the overhanging region 19, a dispersion plate 25, a mixer 26, and a cylindrical member 27 are arranged. The dispersion plate 25 is a member for dispersing the reducing agent K in the exhaust gas G passing through the exhaust pipe 10. The dispersion plate 25 is configured, for example, by arranging three vanes 25a extending in the radial direction of the exhaust pipe 10 around the central axis. The mixer 26 is a member for mixing the reducing agent K in the exhaust gas G. The mixer 26 is configured, for example, by arranging eight vanes 26a extending in the radial direction of the exhaust pipe 10 around the central axis.

[0026] Both the vanes 25a and 26a are inclined at a predetermined angle with respect to the flow direction of the exhaust gas G (axial direction of the exhaust pipe 10) passing through the exhaust pipe 10. The inclination angle of each vane 26a in the mixer 26 may be larger than the inclination angle of each vane 25a in the dispersion plate 25. The width of each vane 26a in the mixer 26 may be larger than the width of each vane 25a in the dispersion plate 25.

[0027] The cylindrical member 27 is a part for holding the dispersion plate 25 and the mixer 26. The cylindrical member 27 is made of a metal material such as stainless steel, for example, and has an outer diameter slightly smaller than the inner diameter of the exhaust pipe 10. The dispersion plate 25 is held on one end side of the cylindrical member 27. The mixer 26 is held on the other end side of the cylindrical member 27. The middle part of the cylindrical member 27 is a spacer part 27a that separates the dispersion plate 25 and the mixer 26 with a predetermined interval. The spacer part 27a has a length L such that the reducing agent K passing through the dispersion plate 25 can collide with the spacer part 27a at least once. In the present embodiment, the length L of the spacer part 27a is such that the reducing agent K passing through the dispersion plate 25 can collide with the inner wall of the spacer part 27a once before hitting the vanes 26a of the mixer 26.

[0028] The cylindrical member 27 is arranged in the exhaust pipe 10 such that the dispersion plate 25 faces the injector 50 at the confluence position of the exhaust gas G and the reducing agent K or on the downstream side thereof, and the mixer 26 is located on the downstream side of the dispersion plate 25. When fixing the cylindrical member 27 to the exhaust pipe 10, a cylindrical bracket 28 for attaching the cylindrical member 27 to the exhaust pipe 10 is provided on the outer peripheral side of the cylindrical member 27. The bracket 28 is made of a metal material such as stainless steel, for example, and has an inner diameter that is slightly larger than the outer diameter of the cylindrical member 27.

[0029] In the present embodiment, the bracket 28 is located at the overlapping portion R between the downstream end portion 20a of the first heat insulator 20 and the upstream end portion 30a of the second heat insulator 30. The bracket 28 is firmly fixed to the exhaust pipe 10 at the position of the overlapping portion R, for example, by welding. In the fixed state to the exhaust pipe 10, a gap portion S through which the exhaust gas G can flow is provided between the bracket 28 and the exhaust pipe 10. There is no particular limitation on the width of the gap portion S in the radial direction of the exhaust pipe 10, but as an example, it can be made approximately the same as the thickness of the wall portion of the exhaust pipe 10.

[0030] In the exhaust pipe structure 1 as described above, as shown in FIG. 3, the exhaust gas G flowing from the upstream side of the exhaust pipe 10 and the reducing agent K introduced from the injector 50 into the exhaust pipe 10 merge in the overhanging region 19. When the main stream of the exhaust gas G into which the reducing agent K has merged collides with the dispersion plate 25 on one end side of the cylindrical member 27, the reducing agent K is dispersed in the exhaust gas G. The reducing agent K collides with the blades 25a of the dispersion plate 25 while being pushed downward by the flow of the exhaust gas G from above.

[0031] The reducing agent K passing through the dispersion plate 25 collides with the inner wall of the spacer portion 27a in the cylindrical member 27 while being dispersed in the exhaust gas G, and collides with the blades 26a of the mixer 26 on the other end side of the cylindrical member 27 while bouncing upward. The reducing agent K that has collided with the blades 26a of the mixer 26 is more uniformly mixed in the exhaust gas G and flows downstream of the exhaust pipe 10 together with the main flow of the exhaust gas G. A part of the exhaust gas G flowing through the exhaust pipe 10 does not pass through the dispersion plate 25 and the mixer 26, but passes through the gap portion S between the cylindrical member 27 and the bracket 28. The exhaust gas G that has passed through the gap portion S merges with the main flow of the exhaust gas G that has passed through the dispersion plate 25 and the mixer 26 on the downstream side of the cylindrical member 27.

[0032] As described above, in the exhaust pipe structure 1, in the cylindrical member 27 that holds the dispersion plate 25 and the mixer 26, a spacer portion 27a that separates the dispersion plate 25 and the mixer 26 at a predetermined interval is provided. By separating the dispersion plate 25 and the mixer 26, the mixing of the reducing agent K in the exhaust gas G by the mixer 26 can proceed in a state where the reducing agent K is sufficiently dispersed in the exhaust gas G by the dispersion plate 25, and it is possible to suppress the reducing agent K from passing through both the dispersion plate 25 and the mixer 26. Therefore, the dispersibility of the reducing agent K with respect to the exhaust gas G can be enhanced. Further, in the exhaust pipe structure 1, since the spacer portion 27a exists between the dispersion plate 25 and the mixer 26, the main flow that has become thin at the confluence position of the exhaust gas G and the reducing agent K will flow toward the mixer 26 in a state where it has widened to some extent. Therefore, the retention of the main flow in the vicinity of the mixer 26 can be suppressed, and an increase in pressure loss can be suppressed.

[0033] In the exhaust pipe structure 1, the spacer portion 27a has a length L such that the reducing agent K passing through the dispersion plate 25 can collide with the spacer portion 27a at least once. Thereby, the mixing of the reducing agent K in the exhaust gas G by the mixer 26 can proceed in a state where the reducing agent K is more surely dispersed in the exhaust gas G. Therefore, it is possible to further enhance the dispersibility of the reducing agent K with respect to the exhaust gas G.

[0034] In the exhaust pipe structure 1, the cylindrical member 27 is joined to the exhaust pipe 10 via the bracket 28. Thereby, the dispersion plate 25 and the mixer 26 can be firmly held within the exhaust pipe 10. Further, the heat retention effect of the exhaust gas G by the cylindrical member 27 is enhanced by the bracket 28, and the evaporation of the reducing agent K can be promoted.

[0035] In the exhaust pipe structure 1, a gap portion S through which the exhaust gas G can flow is provided between the bracket 28 and the exhaust pipe 10. When a part of the high-temperature exhaust gas G flows through this gap portion S, the heat retention effect of the exhaust gas G by the cylindrical member 27 is further enhanced. Therefore, the evaporation of the reducing agent K can be promoted more effectively.

[0036] The present disclosure is not limited to the above-described embodiment. For example, in the above-described embodiment, the length L of the spacer portion 27a has a length that allows the reducing agent K that has passed through the dispersion plate 25 to collide with the spacer portion 27a once. However, the length L of the spacer portion 27a may be a length such that the reducing agent K that has passed through the dispersion plate 25 hits the blade 26a of the mixer 26 without colliding with the spacer portion 27a. In this case, since the position of the mixer 26 is closer to the dispersion plate 25, the distance from the mixer 26 to the SCR downstream of the exhaust pipe 10 can be secured. Therefore, the mixing of the reducing agent K in the exhaust gas G can proceed sufficiently until it reaches the SCR.

[0037] The length L of the spacer portion 27a may be a length that allows the reducing agent K that has passed through the dispersion plate 25 to collide with the spacer portion 27a two or more times. In this case, the reducing agent K can be more sufficiently dispersed in the exhaust gas G before hitting the blade 26a of the mixer 26. Further, the gap portion S between the cylindrical member 27 and the bracket 28 does not necessarily have to be provided. Even when a part of the exhaust gas G is not allowed to flow through the gap portion S, the heat retention effect of the exhaust gas G by the cylindrical member 27 is sufficiently exhibited by the bracket 28.

Description of Reference Numerals

[0038] 1... Exhaust pipe structure, 10... Exhaust pipe, 25... Dispersion plate, 26... Mixer, 27... Cylindrical member, 27a... Spacer portion, 28... Bracket, 50... Injector, S... Gap portion, G... Exhaust gas, K... Reducing agent.

Claims

1. An exhaust pipe structure connected to an internal combustion engine of a vehicle, an exhaust pipe for flowing exhaust gas, an injector for introducing a reducing agent into the exhaust pipe, a dispersion plate disposed at a confluence position of the exhaust gas and the reducing agent or on the downstream side thereof, for dispersing the reducing agent in the exhaust gas, a mixer disposed on the downstream side of the dispersion plate, for mixing the reducing agent in the exhaust gas, and a cylindrical member for holding the dispersion plate and the mixer, the mixer has a plurality of blades disposed around the axis of the exhaust pipe, and the plurality of blades have an inclination in the rotational direction with respect to an axis extending in the radial direction of the exhaust pipe, the cylindrical member has a spacer portion for separating the dispersion plate and the mixer at a predetermined interval, at the confluence position, the flow direction of the exhaust gas and the flow direction of the reducing agent intersect, the dispersion plate has a plurality of blades disposed around the axis of the exhaust pipe, the spacer portion has a length such that the reducing agent that has passed through without colliding with the plurality of blades of the dispersion plate can collide with the spacer portion at least once. An exhaust pipe structure.

2. The exhaust pipe structure according to claim 1, wherein the cylindrical member is joined to the exhaust pipe via a bracket.

3. The exhaust pipe structure according to claim 2, wherein a gap portion through which the exhaust gas can flow is provided between the bracket and the exhaust pipe.

4. The exhaust pipe structure according to any one of claims 1 to 3, wherein the dispersion plate and the cylindrical member are separate members.

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