JP2018150895A - Exhaust emission control device - Google Patents

Abstract

An exhaust purification device that uniformly supplies a reducing agent to an end face of an exhaust purification catalyst is provided. An exhaust emission control device includes an exhaust pipe, a catalyst for purifying exhaust gas, an addition valve section for adding a reducing agent, and a dispersion section for dispersing a reducing agent injected from the addition valve section. And. The exhaust pipe 20 includes a downstream portion 21 where the catalyst 11 and the dispersion portion 12 are disposed, an upstream portion 22, and a curved portion 23. The addition valve part 13 is provided in the bending part 23 so that the injection opening part 14 faces the dispersion part 12. The bending portion 23 is provided with a guide wall 50 whose tip 50B is directed toward the bending inner peripheral wall 28. The guide wall 50 is provided such that the distal end 50B is positioned on the exhaust upstream side of the base end 50A, and the curved inner peripheral wall is warped so as to form a concave curved surface 51. The distal end 50B of the guide wall 50 is located on the downstream portion 21 side of the injection opening 14 and on the curved outer peripheral wall 24 side. [Selection] Figure 1

Description

  The present invention relates to an exhaust purification device that purifies exhaust gas from an internal combustion engine.

  2. Description of the Related Art An exhaust gas purification apparatus for an internal combustion engine that includes an exhaust pipe provided with a catalyst that purifies exhaust gas and an addition valve that adds a reducing agent to the catalyst is known. In the exhaust emission control device disclosed in Patent Document 1, the exhaust pipe has a downstream direction in which the central axis of the pipe extends in a downstream portion where the catalyst is arranged, and a central axis of the pipe in a portion upstream of the portion where the catalyst is arranged. Is different from the upstream direction. The exhaust pipe is curved at a portion where the downstream direction and the upstream direction intersect with each other, and an addition valve is disposed in the curved curved portion. A dispersion plate is disposed downstream of the exhaust pipe and upstream from the catalyst, and the reducing agent injected from the addition valve is dispersed toward the catalyst by the dispersion plate.

JP 2016-186277 A

  In the exhaust emission control device disclosed in Patent Document 1, the addition valve is fixed to the curved portion of the exhaust pipe so that the injection hole faces the dispersion plate. However, since the curved portion of the exhaust pipe is a portion where the flow of exhaust gas is changed in the exhaust pipe, the exhaust flowing through the curved portion tends to be directed to the wall surface on the curved outer peripheral side. For this reason, depending on the bending mode of the exhaust pipe and the flow rate of the exhaust, the reducing agent injected from the addition valve receives the influence of the exhaust flowing through the bending portion, so that the reducing agent is biased toward a part of the dispersion plate. Therefore, there is a problem that the reducing agent that reaches the end face of the catalyst is difficult to be uniformly dispersed.

Hereinafter, means for solving the above-described problems and the effects thereof will be described.
An exhaust emission control device for solving the above problems includes an exhaust pipe that forms an exhaust passage of an internal combustion engine, a catalyst that purifies exhaust, an addition valve portion that adds a reducing agent, and a reduction injected from the addition valve portion. An exhaust purification device comprising a dispersion part for dispersing the agent, wherein the exhaust pipe has a downstream part in which the catalyst is arranged and extends linearly, and an exhaust upstream side of the downstream part. An upstream portion that is linearly extended so as to intersect the extending direction of the downstream portion, and a portion that intersects the extending direction of the downstream portion and the extending direction of the upstream portion The dispersing portion is provided in the downstream portion, and the addition valve portion is provided in the bending portion so that the injection opening of the reducing agent is directed to the dispersing portion. And the bending portion has a proximal end on the outer peripheral wall surface of the bending portion and a distal end. A guide wall directed toward the inner peripheral wall surface of the bending portion is projected, and the guide wall is provided such that its distal end is located on the exhaust upstream side of the base end, The circumferential wall surface is curved so as to form a concave curved surface, the tip of the guide wall is located on the downstream side of the injection opening, and from the end of the injection opening on the downstream side The gist thereof is that the tip of the guide wall is located on the curved outer peripheral side with respect to any virtual straight line extending along the central axis direction of the injection opening.

  In a curved exhaust pipe, due to the centrifugal force acting on the exhaust gas that passes through the curved portion and the pressure difference between the curved inner peripheral side and the curved outer peripheral side of the curved portion, in a direction crossing the main flow of the exhaust Circulating vortices may occur. According to the above configuration, the vortex generated on the downstream side of the bending portion can be guided by the guide wall. That is, the concave curved surface of the guide wall forms an exhaust flow from the downstream side to the upstream side and from the curved outer peripheral side to the curved inner peripheral side on the exhaust upstream side of the dispersion portion. By such a vortex flow, the main flow of exhaust gas that tends to be directed to the wall surface on the curved outer circumferential side can be guided to the curved inner circumferential side. Further, the reducing agent injected from the addition valve portion is also guided to the inner circumferential side by the vortex flow guided by the guide wall. That is, the injected reducing agent is prevented from colliding with the wall surface on the curved outer peripheral side due to the influence of the exhaust flow, and the reducing agent is suppressed from being supplied only to a part of the dispersion portion.

The figure which shows the cross-section about one Embodiment of an exhaust gas purification apparatus. The figure which shows typically the exhaust gas which flows through the exhaust gas purification apparatus concerning the embodiment.

Hereinafter, an embodiment of an exhaust emission control device will be described with reference to FIG.
As shown in FIG. 1, an exhaust purification device 10 for an internal combustion engine includes a catalyst 11 that selectively reduces NOx contained in exhaust gas in an exhaust pipe 20. The catalyst 11 is disposed in the downstream portion 21 of the exhaust pipe 20 that forms the exhaust passage. The downstream portion 21 of the exhaust pipe 20 is disposed so as to be positioned below the vehicle on which the internal combustion engine is mounted. The downstream portion 21 extends in a straight line, and is mounted so that the central axis C1 of the downstream portion 21 is parallel to the horizontal direction.

  In the downstream portion 21 of the exhaust pipe 20, a dispersion portion 12 for dispersing a reducing agent injected from an addition valve 17 described later is disposed on the exhaust upstream side of the catalyst 11. FIG. 1 shows a central portion 12 </ b> A of the dispersion portion 12. The central portion 12A is located on the central axis C1 of the downstream portion 21. The dispersion part 12 is configured by extending a plurality of strip-like dispersion plates from the inner wall of the exhaust pipe 20 toward the central axis C1.

  The exhaust pipe 20 has an upstream portion 22 extending upstream of the downstream portion 21 so as to intersect with the extending direction of the central axis C <b> 1 in the downstream portion 21. The upstream portion 22 is linearly extended so that the central axis C2 of the upstream portion 22 is inclined downward from the exhaust upstream side to the downstream side.

  In the exhaust pipe 20, a curved portion 23 is provided at a portion where the central axis C1 of the downstream portion 21 and the central axis C2 of the upstream portion 22 intersect. The central axis of the curved portion 23 is curved in an arc shape from the downstream end portion of the upstream portion 22 toward the upstream end portion of the downstream portion 21. A hole 25 is formed in the curved outer peripheral wall 24 which is a wall surface on the curved outer peripheral side of the curved portion 23. The addition valve portion 13 is inserted into the hole 25. The addition valve unit 13 is provided with an addition valve 17 for supplying urea water as a reducing agent to the catalyst 11. The addition valve part 13 has a connection part 15 inserted in the exhaust pipe 20 and a heat radiation part 16 covering the addition valve 17. The heat radiation part 16 is provided with heat radiation fins 16A. The addition valve 17 is fixed to the curved portion 23 of the exhaust pipe 20 via the addition valve portion 13. The injection opening 14 located on the bending portion 23 side in the connection portion 15 of the addition valve portion 13 protrudes into the bending portion 23. The injection hole 17 </ b> A of the addition valve 17 is located at the end of the heat radiating part 16 on the connection part 15 side. The injection hole 17 </ b> A of the addition valve 17 is directed to the dispersion unit 12. The addition valve portion 13 is disposed so that the central axis C3 that is the extending direction of the connecting portion 15 in the addition valve portion 13 coincides with the central axis C1 that is the extending direction of the downstream portion 21.

  In the curved outer peripheral wall 24 of the curved portion 23, a gentle gradient portion 27 is formed on the exhaust upstream side of the hole 25. The gradient of the gentle gradient portion 27 is gentler than the gradient of the central axis C2 with respect to the central axis C1.

  A guide wall 50 having a proximal end 50 </ b> A located on the curved outer peripheral wall 24 of the curved portion 23 is projected from the exhaust pipe 20. The guide wall 50 is provided such that the distal end 50B is located on the exhaust upstream side of the base end 50A. The distal end 50 </ b> B of the guide wall 50 is directed to the curved inner peripheral wall 28 that is the wall surface on the curved inner peripheral side of the bending portion 23. The distal end 50B of the guide wall 50 is located on the downstream portion 21 side with respect to the injection opening 14.

  Here, when an imaginary straight line is extended from the end of the injection opening 14 on the downstream portion 21 side along the extending direction of the central axis C3 that is the central axis of the injection opening 14 projecting into the curved portion 23 A virtual straight line extending most from the curved outer peripheral wall 24 side in the end portion is shown in FIG. 1 as a virtual straight line L1. The distal end 50B of the guide wall 50 is located closer to the curved outer peripheral wall 24 than the virtual straight line L1. That is, the front end 50 </ b> B of the guide wall 50 is located closer to the curved outer peripheral wall 24 than any virtual straight line extending from the end of the injection opening 14.

  In addition, the guide wall 50 has a concave curved surface 51 on the inner circumferential side. That is, the guide wall 50 is warped on the downstream portion 21 side. A back surface 52 that is a wall surface on the curved outer peripheral side of the guide wall 50 is separated from the curved outer peripheral wall 24. The space | interval which the back surface 52 and the curved outer peripheral wall 24 are spaced apart is large toward the front end 50B side. By providing the guide wall 50, the portion of the curved inner periphery side of the guide wall 50 in the passage sectional area of the curved portion 23 at the position of the distal end 50B is the passage sectional area of the curved portion 23 at the position of the base end 50A. Is smaller than The injection opening 14 is located closer to the curved outer peripheral wall 24 than the imaginary line L2 connecting the tip 50B of the guide wall 50 and the downstream end 27A of the gentle gradient portion 27.

Next, the effect of the exhaust emission control device 10 according to this embodiment will be described.
In an exhaust pipe that is curved like the exhaust pipe 20 provided in the exhaust purification device 10, a vortex that circulates in a direction intersecting the main flow of exhaust may occur in the curved portion 23. More specifically, the flow generated from the curved inner peripheral side toward the curved outer peripheral side by the centrifugal force of the exhaust gas passing through the curved portion 23, and the exhaust gas pushed to the curved outer peripheral side along with the flow generated by the centrifugal force are exhaust pipes. On the wall surface side of 20, a flow that flows away from the curved outer peripheral side to the curved inner peripheral side is generated. According to the exhaust purification device 10, this vortex can be guided to the curved inner peripheral side by the guide wall 50.

  FIG. 2 illustrates the vortex S1 and the vortex S2 generated on the upstream portion 22 side of the vortex S1 as vortices to be generated. Since the guide wall 50 is warped so as to form the concave curved surface 51, the vortex S2 is pushed up to the curved inner peripheral side with respect to the vortex S1. The main flow of the exhaust gas flowing into the curved portion 23 from the upstream portion 22 is guided to the curved inner peripheral side like the main flow S3 of the exhaust gas shown in FIG. 2 by the flow exemplified as the vortex S1 and the vortex S2. That is, according to the exhaust gas purification apparatus 10, the exhaust gas can be guided so that the main flow S <b> 3 of the exhaust gas is directed to the central portion 12 </ b> A of the dispersion portion 12. This suppresses the exhaust from colliding with the curved outer peripheral wall 24.

  Further, the exhaust gas passing through the curved portion 23 is easily separated from the curved inner peripheral wall 28 on the downstream portion 21 side in the curved portion 23, but according to the exhaust purification device 10, the exhaust gas can be pushed up to the curved inner peripheral side. As exemplified in the main flow S3 of the exhaust, the exhaust is easily guided to the vicinity of the central portion 12A of the dispersion portion 12.

  Further, the exhaust gas that flows into the curved portion 23 from the upstream portion 22 and flows on the curved outer peripheral side collides with the gentle gradient portion 27 and peels off, and is pushed up to the curved inner peripheral side by the vortex guided to the guide wall 50. It flows to the downstream part 21 side. For this reason, the flow of exhaust differs between the curved inner peripheral side and the curved outer peripheral side with reference to an imaginary line L2 connecting the tip 50B of the guide wall 50 and the downstream end 27A of the gentle gradient portion 27. That is, in the region on the curved outer circumference side with respect to the imaginary line L2, the gas does not flow easily, and the exhaust flow hardly changes. By providing the injection opening 14 in such a region, the addition valve 17 is not easily exposed to the flow of exhaust gas, and the tip temperature of the addition valve 17 increases due to the heat of the exhaust gas being transmitted to the addition valve 17. Can be suppressed. If the tip temperature of the addition valve 17 rises excessively, deposits derived from the reducing agent may be deposited around the injection hole 17A, but the exhaust purification device 10 can suppress the rise in the tip temperature of the addition valve 17. According to this, it is possible to suppress deposits from being accumulated at the tip of the addition valve 17.

  According to the exhaust gas purification apparatus 10, the main flow S3 of the exhaust gas is induced by vortices. Therefore, even if the exhaust gas flow rate flowing through the exhaust pipe 20 increases, the exhaust gas flowing through the curved portion 23 is less likely to be directed to the curved outer peripheral wall 24. Thus, the reducing agent dispersed uniformly regardless of the flow rate of the exhaust can reach the end face of the catalyst 11.

  Further, according to the exhaust gas purification apparatus 10, the exhaust gas is guided so as to be directed to the central portion 12 </ b> A of the dispersion portion 12, so that the reducing agent injected from the addition valve 17 is washed away by the exhaust gas and adheres to the curved outer peripheral wall 24. This is suppressed. Further, the reducing agent injected from the addition valve 17 can be pushed up to the inner side of the curve by the vortex guided to the guide wall 50. As a result, the reducing agent easily flows along the flow of exhaust gas directed to the central portion 12A of the dispersing portion 12, and the reducing agent is easily dispersed by the dispersing portion 12. Further, since the injected reducing agent tends to intersect with the vortex and the main flow of the exhaust, the reducing agent tends to be sprayed with fine particles on the exhaust upstream side of the dispersion portion 12. This makes it easier for the reducing agent to be dispersed. That is, the reducing agent that reaches the end face of the catalyst 11 is easily dispersed uniformly.

  Further, the tip 50B of the guide wall 50 is located closer to the curved outer peripheral wall 24 than the virtual straight line L1. As a result, the reducing agent that is injected from the addition valve 17 and flows to the downstream portion 21 side is prevented from being blocked by the guide wall 50. That is, it can suppress that a reducing agent adheres to the guide wall 50. FIG.

In addition, the said embodiment can also be implemented with the following forms which changed this suitably.
In the above embodiment, a dispersion plate is illustrated as the dispersion unit 12. The dispersion unit 12 may have a configuration capable of dispersing the reducing agent supplied to the catalyst 11. For example, a grid-like plate provided over the entire passage section in the exhaust pipe 20 can also be employed.

  -The central axis C1 of the downstream part 21 and the central axis C3 of the connection part 15 do not necessarily need to correspond. The injection hole 17 </ b> A of the addition valve 17 provided in the addition valve portion 13 only needs to be directed to the dispersion portion 12.

-The base end 50A of the guide wall 50 should just be located in the downstream part 21 side rather than the injection opening part 14 in the curved part 23. FIG.
The guide wall 50 is not limited to the illustrated shape as long as the curved inner peripheral wall is warped so as to form the concave curved surface 51 and the tip 50B is directed to the curved inner peripheral wall 28. For example, the distance at which the back surface 52 of the guide wall 50 and the curved outer peripheral wall 24 are separated can be changed. Further, if the distal end 50B is located on the downstream portion 21 side and the curved outer peripheral wall 24 side with respect to the injection opening 14, the length from the proximal end 50A to the distal end 50B can be changed.

  DESCRIPTION OF SYMBOLS 10 ... Exhaust gas purification apparatus, 11 ... Catalyst, 12 ... Dispersion part, 12A ... Center part, 13 ... Addition valve part, 14 ... Injection opening part, 15 ... Connection part, 16 ... Radiation part, 16A ... Radiation fin, 17 ... Addition Valves, 17A ... injection holes, 20 ... exhaust pipe, 21 ... downstream part, 22 ... upstream part, 23 ... curved part, 24 ... curved outer peripheral wall, 25 ... hole, 27 ... gentle gradient part, 27A ... downstream end, 28 ... Curved inner peripheral wall, 50 ... guide wall, 50A ... base end, 50B ... tip, 51 ... concave curved surface, 52 ... back surface.

Claims (1)

Exhaust gas purification comprising an exhaust pipe that forms an exhaust passage of an internal combustion engine, a catalyst that purifies exhaust gas, an addition valve portion that adds a reducing agent, and a dispersion portion that disperses the reducing agent injected from the addition valve portion A device,
The exhaust pipe extends linearly so that the downstream side where the catalyst is disposed and extends linearly and the upstream side of the downstream part and the direction of extension of the downstream part intersect. An upstream portion, and a curved portion curved in an arc shape at a portion where the extending direction of the downstream portion and the extending direction of the upstream portion intersect,
The dispersion portion is provided in the downstream portion, and the addition valve portion is provided in the curved portion so that a reducing agent injection opening is directed to the dispersion portion,
The bending portion has a guide wall protruding from the curved outer peripheral wall surface of the bending portion and having a distal end directed to the curved inner peripheral wall surface of the bending portion. It is provided so as to be located on the exhaust upstream side from the base end, and the wall surface on the curved inner peripheral side is warped so as to form a concave curved surface, and the guide wall is located on the downstream side of the injection opening. The distal end is positioned, and the distal end of the guide wall is positioned on the curved outer peripheral side from any imaginary straight line extending from the downstream end of the ejection opening along the central axis direction of the ejection opening. Exhaust purification device.