JP7694367B2 - Exhaust pipe structure - Google Patents

Description

This disclosure relates to an exhaust pipe structure.

As an example of a conventional exhaust pipe structure, there is an exhaust gas purification device described in Patent Document 1. This conventional exhaust gas purification device is provided with a diffusion member that is provided upstream of the expanded diameter flow passage in the exhaust gas flow passage and causes exhaust gas flowing in from the upstream side to flow out so as to diffuse into the expanded diameter flow passage, and a supply device that supplies reducing agent to the exhaust gas flow passage upstream of the diffusion member. In addition, at the junction position where the reducing agent and the exhaust gas join, a guide member is provided that branches the flow of reducing agent into multiple parts and guides them to the diffusion member.

For example, the exhaust purification device described in Patent Document 2 has an injector having a cylindrical injector body provided in the exhaust pipe. The injector body is inserted into the exhaust pipe. One end of the injector body is provided with a nozzle attachment part to which a nozzle for spraying reducing agent is attached, and the other end is provided with a control vane for diffusing the sprayed reducing agent.

JP 2014-100628 A JP 2020-045774 A

The diffusion member in the exhaust gas purification device described in Patent Document 1 has the function of suppressing bias in the flow of exhaust gas in the expanded diameter flow passage, but is not thought to have the function of dispersing the reducing agent that is unevenly present in the exhaust gas. In particular, if the supply direction of the reducing agent differs from the flow direction of the exhaust gas at the position where the exhaust gas and the reducing agent join, the flow of the reducing agent may easily become biased due to the influence of the exhaust gas flow.

In the exhaust purification device described in Patent Document 2, an intake opening is provided on the side wall of the injector body inserted into the exhaust pipe to take in exhaust gas. The reducing agent introduced into the injector body collides with a backing plate inside the injector body together with the exhaust gas taken into the injector body from the intake opening, and is dispersed into the exhaust gas. However, with the configuration of Patent Document 2, there is a concern that the pressure loss of the exhaust gas near the intake opening increases, affecting the performance of the internal combustion engine.

This disclosure has been made to solve the above problems, and aims to provide an exhaust pipe structure that can increase the dispersion of reducing agents in exhaust gas while suppressing an increase in pressure loss.

The 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, and includes an exhaust pipe for circulating exhaust gas, an injector for introducing a reducing agent into the exhaust pipe, a dispersion plate disposed at or downstream of the confluence of the exhaust gas and the reducing agent for dispersing the reducing agent in the exhaust gas, a mixer disposed downstream 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 cylindrical member having a spacer portion for separating the dispersion plate and the mixer by a predetermined distance.

In this exhaust pipe structure, a spacer portion is provided in the cylindrical member that holds the dispersion plate and the mixer, separating the dispersion plate and the mixer by a predetermined distance. By separating the dispersion plate and the mixer, the mixer can proceed with mixing the reducing agent in the exhaust gas with the reducing agent sufficiently dispersed in the exhaust gas by the dispersion plate, and the reducing agent can be prevented from slipping through both the dispersion plate and the mixer. Therefore, the dispersion of the reducing agent in the exhaust gas can be improved. In addition, in this exhaust pipe structure, the spacer portion exists between the dispersion plate and the mixer, so that the main flow that narrows at the confluence of the exhaust gas and the reducing agent heads toward the mixer in a state of being somewhat widened. Therefore, the main flow is prevented from stagnation near the mixer, and an increase in pressure loss can be prevented.

The spacer portion may have a length that allows the reducing agent that has passed through the dispersion plate to collide with the spacer portion at least once. This allows the mixer to proceed with mixing of the reducing agent in the exhaust gas with the reducing agent being more reliably dispersed in the exhaust gas. This makes it possible to further improve the dispersibility of the reducing agent in the exhaust gas.

The cylindrical member may be joined to the exhaust pipe via a bracket. This allows the dispersion plate and mixer to be held firmly inside the exhaust pipe. The bracket also enhances the thermal insulation effect of the cylindrical member on the exhaust gas, facilitating the evaporation of the reducing agent.

A gap may be provided between the bracket and the exhaust pipe through which exhaust gas can flow. In this case, a portion of the high-temperature exhaust gas flows through the gap, further enhancing the heat retention effect of the tubular member on the exhaust gas. This can therefore promote the evaporation of the reducing agent even more effectively.

According to the present disclosure, it is possible to increase the dispersion of the reducing agent in the exhaust gas while suppressing an increase in pressure loss.

FIG. 2 is a side view showing the upstream side of the exhaust pipe structure according to the embodiment of the present disclosure. 2 is an enlarged perspective view showing the vicinity of a main part of the exhaust pipe structure shown in FIG. 1 . 2 is a cross-sectional view showing the vicinity of a main part of the exhaust pipe structure shown in FIG. 1.

A preferred embodiment of an exhaust pipe structure according to one aspect of the present disclosure will be described in detail below with reference to the drawings. For ease of explanation, the terms "upper" and "lower" will be used below based on the state in which the exhaust pipe is attached to the vehicle. Additionally, the terms "upper" and "downstream" will be used below based on the flow direction of exhaust gas in the exhaust pipe.

1 is a side view showing the upstream side of an exhaust pipe structure according to an embodiment of the present disclosure. FIG. 2 is an enlarged perspective view showing the vicinity of a 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 an exhaust pipe 10 is insulated by a first heat insulator 20 and a second heat insulator 30. The exhaust pipe 10 is made of a metal material such as stainless steel. The exhaust pipe 10 has a protruding region 19 that protrudes vertically downward due to bending or swelling of the exhaust pipe 10. The first heat insulator 20 is arranged to cover the exhaust pipe 10 upstream of the protruding region 19. The second heat insulator 30 is arranged to cover the exhaust pipe 10 downstream of the protruding region 19.

The exhaust pipe 10 is connected to an internal combustion engine mounted on a vehicle, and constitutes an exhaust passage that discharges exhaust gas generated by combustion in the combustion chamber of the internal combustion engine. When connected to the internal combustion engine, the exhaust pipe 10 extends, for example, along the front-to-rear direction of the vehicle. An example of an 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, dump trucks, etc.

For example, a turbocharger, a diesel oxidation catalyst (DOC), a diesel particulate filter (DPF), etc. are provided upstream of the exhaust pipe 10. For example, a selective catalytic reduction (SCR) is provided downstream of the exhaust pipe 10. In the example of Fig. 1 and Fig. 2, an injector 50 for injecting a reducing agent (e.g., urea water) into the SCR is disposed in the exhaust pipe 10. The injector 50 is attached to a wall of the exhaust pipe 10 so as to face the downstream side of the exhaust pipe 10.

As shown in FIG. 1, the exhaust pipe 10 has a connection 11 and bent portions 12, 13, and 14 on the upstream side. The connection 11 is connected to another exhaust pipe arranged on the upstream side (the internal combustion engine side) of the exhaust pipe 10. The straight portion 15 extending from the connection 11 is inclined downward toward the injector 50 to match the piping path of the upstream exhaust pipe. The bent portion 12 bends the exhaust pipe 10 so that the downward inclination of the straight portion 16 extending downstream from the bent portion 12 is smaller than the downward inclination of the straight portion 15. The extension direction of the straight portion 15 downstream of the bent portion 12 is more aligned with the direction of the injector 50 than the straight portion 15.

The bent portion 13 is provided near the base end of the injector 50. The bent portion 13 bends the exhaust pipe 10 so that the downward inclination of the straight portion 17 downstream of the bent portion 13 is greater than the downward inclination of the straight portion 16. The straight portion 17 downstream of the bent portion 13 extends downward toward the mounting position of the injector 50. The bent portion 14 bends the exhaust pipe 10 immediately downstream of the bent portion 13 so that the straight portion 18 downstream of the injector 50 extends generally along the axial direction of the injector 50. The straight portion 18 downstream of the injector 50 extends at a slight upward inclination with respect to the horizontal plane.

These bends 12, 13, and 14 allow the piping path of the exhaust pipe 10 to avoid interference with, for example, the lower structure of the vehicle (such as the cross member of the suspension). In addition, the injector 50, which is installed to inject reducing agent toward the rear of the vehicle, makes it possible to inject reducing agent downstream inside the exhaust pipe 10.

The exhaust pipe 10 has a protruding region 19 that protrudes due to bending of the bent portion 14. That is, in the exhaust pipe 10, a certain range downstream of the bent portion 14 is the protruding region 19 formed by bending the bent portion 14. As an example, the protruding region 19 is a region that includes the point located vertically lowest (the point with the smallest ground height) in the exhaust passage including the exhaust pipe 10.

As shown in FIG. 2, the first heat insulator 20 has a pair of heat shield plates 21, 22 provided along the outer surface of the exhaust pipe 10 upstream of the protruding region 19. The second heat insulator 30 has a pair of heat shield plates 31, 32 provided along the outer surface of the exhaust pipe 10 downstream of the protruding region 19. When viewed from the axial direction of the exhaust pipe 10, the first heat insulator 20 has a left-right split structure with the heat shield plates 21, 22. Similarly, when viewed from the axial direction of the exhaust pipe 10, the second heat insulator 30 has a left-right split structure with the heat shield plates 31, 32.

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 that is circumferentially aligned with the exhaust pipe 10 and communicates with the outside. In this embodiment, the upstream end 30a of the second heat insulator 30 expands in diameter at the overlapping portion R and is disposed so as to be radially outward of the exhaust pipe 10 relative to the downstream end 20a of the first heat insulator 20. A wire mesh 40 is disposed in the gap portion. The wire mesh 40 is formed of, for example, stainless steel. The wire mesh 40 allows liquids such as water to pass through while capturing foreign matter such as dead grass.

Figure 3 is a cross-sectional view showing the vicinity of the main part of the exhaust pipe structure shown in Figure 1. As shown in the figure, a dispersion plate 25, a mixer 26, and a cylindrical member 27 are arranged in the exhaust pipe 10 in correspondence with the protruding region 19. The dispersion plate 25 is a member that disperses 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 blades 25a extending in the radial direction of the exhaust pipe 10 around a central axis. The mixer 26 is a member that mixes the reducing agent K in the exhaust gas G. The mixer 26 is configured, for example, by arranging eight blades 26a extending in the radial direction of the exhaust pipe 10 around a central axis.

The blades 25a, 26a are both inclined at a predetermined angle with respect to the flow direction of the exhaust gas G passing through the exhaust pipe 10 (the axial direction of the exhaust pipe 10). The inclination angle of each blade 26a in the mixer 26 may be larger than the inclination angle of each blade 25a in the distribution plate 25. The width of each blade 26a in the mixer 26 may be larger than the width of each blade 25a in the distribution plate 25.

The cylindrical member 27 is a portion that holds the dispersion plate 25 and the mixer 26. The cylindrical member 27 is made of a metal material such as stainless steel, and has an outer diameter that is slightly smaller than the inner diameter of the exhaust pipe 10. The dispersion plate 25 is held at one end of the cylindrical member 27. The mixer 26 is held at the other end of the cylindrical member 27. The middle portion of the cylindrical member 27 is a spacer portion 27a that separates the dispersion plate 25 and the mixer 26 at a predetermined distance. The spacer portion 27a has a length L that allows the reducing agent K that has passed through the dispersion plate 25 to collide with the spacer portion 27a at least once. In this embodiment, the length L of the spacer portion 27a is a length that allows the reducing agent K that has passed through the dispersion plate 25 to collide with the inner wall of the spacer portion 27a once before hitting the blades 26a of the mixer 26.

The cylindrical member 27 is disposed in the exhaust pipe 10 so that the dispersion plate 25 faces the injector 50 at the confluence of the exhaust gas G and the reducing agent K or downstream of the confluence, and the mixer 26 is located downstream of the dispersion plate 25. To fix 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 periphery of the cylindrical member 27. The bracket 28 is made of a metal material such as stainless steel, and has an inner diameter one size larger than the outer diameter of the cylindrical member 27.

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

In the exhaust pipe structure 1 as described above, as shown in FIG. 3, exhaust gas G flowing from the upstream side of the exhaust pipe 10 and reducing agent K introduced into the exhaust pipe 10 from the injector 50 join in the protruding region 19. The main stream of exhaust gas G into which the reducing agent K joins collides with the dispersion plate 25 on one end side of the cylindrical member 27, dispersing the reducing agent K in the exhaust gas G. The reducing agent K collides with the vanes 25a of the dispersion plate 25 while being pushed downward by the flow of exhaust gas G from above.

The reducing agent K that has passed through the dispersion plate 25 collides with the inner wall of the spacer portion 27a of the cylindrical member 27 while dispersing in the exhaust gas G, and then 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 mixed more uniformly in the exhaust gas G and flows downstream of the exhaust pipe 10 together with the mainstream 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 mainstream 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.

As described above, in the exhaust pipe structure 1, the cylindrical member 27 that holds the dispersion plate 25 and the mixer 26 is provided with the spacer portion 27a that separates the dispersion plate 25 and the mixer 26 at a predetermined distance. 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 be advanced in a state in which the reducing agent K is sufficiently dispersed in the exhaust gas G by the dispersion plate 25, and the reducing agent K can be prevented from passing through both the dispersion plate 25 and the mixer 26. Therefore, the dispersion of the reducing agent K in the exhaust gas G can be improved. In addition, in the exhaust pipe structure 1, the spacer portion 27a exists between the dispersion plate 25 and the mixer 26, so that the main flow narrowed at the confluence position of the exhaust gas G and the reducing agent K will head toward the mixer 26 in a state of being somewhat widened. Therefore, the main flow is prevented from stagnation near the mixer 26, and an increase in pressure loss can be suppressed.

In the exhaust pipe structure 1, the spacer portion 27a has a length L that allows the reducing agent K that has passed through the dispersion plate 25 to collide with the spacer portion 27a at least once. This allows the mixer 26 to proceed with mixing of the reducing agent K in the exhaust gas G with the reducing agent K being more reliably dispersed in the exhaust gas G. This makes it possible to further improve the dispersibility of the reducing agent K in the exhaust gas G.

In the exhaust pipe structure 1, the cylindrical member 27 is joined to the exhaust pipe 10 via the bracket 28. This allows the dispersion plate 25 and the mixer 26 to be firmly held inside the exhaust pipe 10. In addition, the bracket 28 enhances the heat retention effect of the cylindrical member 27 on the exhaust gas G, and promotes the evaporation of the reducing agent K.

In the exhaust pipe structure 1, a gap portion S is provided between the bracket 28 and the exhaust pipe 10 through which exhaust gas G can flow. By allowing a portion of the high-temperature exhaust gas G to flow 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 even more effectively.

The present disclosure is not limited to the above embodiment. For example, in the above embodiment, the length L of the spacer portion 27a is long enough for the reducing agent K that has passed through the dispersion plate 25 to collide with the spacer portion 27a once, but the length L of the spacer portion 27a may be long enough for the reducing agent K that has passed through the dispersion plate 25 to collide with the blades 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 be sufficiently advanced before it reaches the SCR.

The length L of the spacer portion 27a may be such that the reducing agent K that has passed through the dispersion plate 25 can collide with the spacer portion 27a two or more times. In this case, the reducing agent K can be more thoroughly dispersed in the exhaust gas G before it hits the blades 26a of the mixer 26. Also, the gap portion S between the cylindrical member 27 and the bracket 28 does not necessarily have to be provided. Even if a portion of the exhaust gas G is not allowed to flow through the gap portion S, the bracket 28 can sufficiently provide the thermal insulation effect of the exhaust gas G by the cylindrical member 27.

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 (4)

An exhaust pipe structure connected to an internal combustion engine of a vehicle,
An exhaust pipe for passing exhaust gas;
an injector that introduces a reducing agent into the exhaust pipe;
a dispersion plate that is disposed at a confluence position of the exhaust gas and the reducing agent or downstream thereof and disperses the reducing agent in the exhaust gas;
a mixer that is disposed downstream of the dispersion plate and mixes the reducing agent in the exhaust gas;
a cylindrical member for holding the dispersion plate and the mixer,
the mixer has a plurality of vanes arranged around an axis of the exhaust pipe, the plurality of vanes having a rotational inclination with respect to an axis extending in a radial direction of the exhaust pipe,
the cylindrical member has a spacer portion that separates the dispersion plate and the mixer at a predetermined interval ,
a flow direction of the exhaust gas and a flow direction of the reducing agent intersect at the joining position,
The dispersion plate has a plurality of vanes arranged around the axis of the exhaust pipe,
An exhaust pipe structure , wherein the spacer portion has a length that allows the reducing agent that has passed through the plurality of vanes of the dispersion plate without colliding with the spacer portion to collide with the spacer portion at least once . 2. The exhaust pipe structure according to claim 1 , wherein the tubular member is joined to the exhaust pipe via a bracket. 3. The exhaust pipe structure according to claim 2 , wherein a gap through which the exhaust gas can flow is provided between the bracket and the exhaust pipe. 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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