JP2016000981A - Exhaust emission control device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve the dispersibility of an additive agent.SOLUTION: An exhaust emission control device 10 includes: an exhaust pipe 1 in which an exhaust gas G flows; a catalyst storage chamber 2 having a passage cross section area larger than a passage cross section area of the exhaust pipe and provided at the downstream side relative to the exhaust pipe, the catalyst storage chamber 2 in which a catalyst 2C is disposed at the inner side; an enlarged diameter part 3 including an upstream side opening part 3A connected with the exhaust pipe and a downstream side opening part 3B connected with the catalyst storage chamber, having a shape in which a passage cross section area gradually increases from the upstream side opening part toward the downstream side opening part, and allowing the exhaust gas from the exhaust pipe to flow to the catalyst storage chamber; and a jet nozzle 4 which has a nozzle tip part 4N, which is disposed so as to be exposed in an inner space of the enlarged diameter part, and jets the additive agent from the nozzle tip part toward the upstream side opening part 3A.

Description

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

  As disclosed in Japanese Patent Application Laid-Open No. 2008-051089 (Patent Document 1) and Japanese Patent Application Laid-Open No. 2007-1000067 (Patent Document 2), an exhaust gas purification device that purifies exhaust gas from an internal combustion engine or the like is known. Yes. This apparatus includes an exhaust pipe and a catalyst, and an additive such as fuel and urea water is injected and supplied to exhaust gas flowing in the exhaust pipe. NOx (nitrogen oxide) contained in the exhaust gas is reduced, and the reduction reaction is promoted by a catalyst provided on the downstream side of the exhaust pipe. The exhaust gas that has passed through the exhaust purification device can be discharged in a purified state.

JP 2008-051089 A JP 2007-1000067 A

  In general, the additive is injected many times at short time intervals. The injected additive flows downstream along with the exhaust gas while being vaporized. The additive is used for purification of exhaust gas, or after being introduced into a catalyst or filter, it is used for regeneration of the filter or the like. The additive is preferably dispersed uniformly after being injected.

  An object of the present invention is to provide an exhaust emission control device having a structure capable of improving the dispersibility of an additive.

  An exhaust emission control device according to the present invention has an exhaust pipe through which exhaust gas flows inside an inner wall surface, a flow passage cross-sectional area larger than the flow passage cross-sectional area of the exhaust pipe, and is downstream of the exhaust pipe. A catalyst containing chamber provided on the inner side and having a catalyst disposed therein, an upstream opening and a downstream opening, the upstream opening being connected to the exhaust pipe, and the downstream opening being the catalyst Connected to the storage chamber, the flow passage cross-sectional area gradually increases from the upstream opening toward the downstream opening, and allows the exhaust gas from the exhaust pipe to flow to the catalyst storage chamber. An enlarged nozzle part, a nozzle tip arranged to be exposed in the inner space of the enlarged part, and an injection nozzle for injecting an additive from the nozzle tip toward the upstream opening; Is provided.

  Preferably, the injection nozzle has a nozzle center axis, and when the virtual center line is drawn by extending the nozzle center axis toward the upstream opening, the virtual extension line is the exhaust pipe. Intersects the inner wall surface and does not intersect the enlarged diameter portion.

  Preferably, the injection nozzle is configured such that the virtual extension line passes through a position just in the center of the upstream opening.

  Preferably, when a virtual extended surface is drawn by extending a conical side surface that defines a spray opening angle of the additive sprayed conically from the injection nozzle, the virtual extended surface is the inner wall surface of the exhaust pipe. Intersects with the above-mentioned enlarged diameter portion.

The diameter d of the inner wall surface of the exhaust pipe, the maximum volume flow rate Q of the exhaust gas flowing through the exhaust pipe, the inclination angle α of the enlarged diameter part with respect to the direction in which the exhaust pipe extends, the nozzle with respect to the enlarged diameter part An inclination angle β of the central axis, an elapsed time t from the time when the additive is injected from the injection nozzle, and a time T from when the additive is injected from the injection nozzle until the speed of the additive becomes zero In the state where the exhaust gas is not passed through the exhaust pipe, the speed U _s (t) of the additive when the time t has elapsed since the additive was injected from the injection nozzle, the exhaust pipe In the state where the exhaust gas is flowing through, the additive velocity U _x (t) when the time t has elapsed since the additive was injected from the injection nozzle, in the direction in which the exhaust pipe extends. , Distance x from the serial upstream opening to any location, and, in the direction in which the exhaust pipe extends, in the case of using the distance L from the upstream opening to the nozzle tip,
The speed U _x (t) is represented by the following equation (1):

  The distance x is represented by the following formula (2):

  The time T is represented by the following formula (3):

  The time T and the distance L satisfy the following expression (4).

Preferably, the exhaust pipe has a substantially rectangular cross-sectional shape.
Preferably, the inner wall surface of the exhaust pipe is located far from the nozzle tip and facing the nozzle tip, and is located closer to the nozzle tip than the facing part. A non-opposing portion that is not opposed to the nozzle tip, and the opposing portion has a shape extending downstream from the non-opposing portion.

  Preferably, the inner wall surface of the exhaust pipe is located far from the nozzle tip and facing the nozzle tip, and is located closer to the nozzle tip than the facing part. A non-opposing portion that is not opposed to the nozzle tip, and the opposing portion is provided with a recess having a shape that is recessed in a direction away from the injection nozzle.

  According to the above idea, an exhaust emission control device having a structure capable of improving the dispersibility of the additive can be obtained.

1 is a cross-sectional view showing an exhaust purification device in Embodiment 1. FIG. It is arrow sectional drawing along the II-II line | wire in FIG. It is sectional drawing which shows a mode that the exhaust gas purification apparatus in Embodiment 1 is operate | moving. It is sectional drawing which shows the exhaust gas purification apparatus in a comparative example. FIG. 6 is a cross-sectional view showing an exhaust purification device (state of operation) in a second embodiment. It is arrow sectional drawing along the VI-VI line in FIG. FIG. 6 is a cross-sectional view showing an exhaust emission control device (state of operation) in Embodiment 3. It is sectional drawing which shows the exhaust gas purification apparatus in Embodiment 4 (state which is operating).

  Hereinafter, embodiments will be described with reference to the drawings. The same parts and corresponding parts are denoted by the same reference numerals, and redundant description may not be repeated.

[Embodiment 1]
With reference to FIGS. 1 to 3, an exhaust purification device 10 according to Embodiment 1 will be described. FIG. 1 is a cross-sectional view showing an exhaust purification device 10. FIG. 2 is a cross-sectional view taken along line II-II in FIG. FIG. 3 is a cross-sectional view showing a state in which the exhaust purification device 10 is operating.

  As shown in FIGS. 1 and 2, the exhaust purification device 10 includes an exhaust pipe 1, a catalyst storage chamber 2 (FIG. 1), an enlarged diameter portion 3 (FIG. 1), and an injection nozzle 4 (FIG. 1). The exhaust pipe 1 of the present embodiment has a circular cross-sectional shape (see FIG. 2). The inner wall surface 1S of the exhaust pipe 1 has a diameter d. Exhaust gas G discharged from an internal combustion engine (not shown) or the like flows through the inner wall surface 1S of the exhaust pipe 1.

The catalyst storage chamber 2 has a substantially cylindrical shape or a substantially rectangular tube shape, and is provided downstream of the exhaust pipe 1 in the direction in which the exhaust gas G flows. The catalyst housing chamber 2 has a larger channel cross-sectional area than the channel cross-sectional area (π × (d / 2) ² ) of the exhaust pipe 1. A catalyst 2 </ b> C is disposed inside the catalyst storage chamber 2. The catalyst 2C is a member for promoting the purification reaction of the exhaust gas G. The exhaust pipe 1 communicates with the catalyst housing chamber 2 through the enlarged diameter portion 3. The exhaust pipe 1 and the enlarged diameter portion 3 guide the exhaust gas G discharged from the internal combustion engine to the catalyst 2C, and bring the exhaust gas G into contact with the catalyst 2C.

  The enlarged diameter portion 3 includes an upstream opening 3A and a downstream opening 3B, and has a cylindrical shape as a whole. The upstream opening 3 </ b> A is connected to the exhaust pipe 1, and the downstream opening 3 </ b> B is connected to the catalyst storage chamber 2. The enlarged diameter portion 3 has a tapered shape in which the flow path cross-sectional area of the enlarged diameter portion 3 gradually increases from the upstream opening 3A toward the downstream opening 3B. The exhaust gas G that has passed through the exhaust pipe 1 flows into the catalyst housing chamber 2 after passing through the enlarged diameter portion 3.

  The injection nozzle 4 has a nozzle tip portion 4N that jets the additive, and the nozzle tip portion 4N is provided in the middle of the enlarged diameter portion 3 in the direction in which the exhaust gas G flows. The nozzle tip 4N is exposed to a space formed inside the enlarged diameter portion 3. In the present embodiment, the nozzle tip portion 4N of the injection nozzle 4 is positioned so that the nozzle tip portion 4N and the inner wall surface 3W of the enlarged diameter portion 3 are located on substantially the same plane. The injection nozzle 4 sprays an additive such as fuel and urea water in a spray form from the nozzle tip 4N toward the upstream opening 3A.

  Here, “the injection nozzle 4 injects the additive from the nozzle tip 4N toward the upstream opening 3A” means from the downstream side to the upstream side in the direction in which the exhaust gas G flows (in FIG. In the case, the additive nozzle flows from the nozzle tip 4N toward the upstream opening 3A so that the additive particles flow and at least a part of the particles opposes the flow of the exhaust gas G). Means to spray.

  The injection nozzle 4 of the present embodiment has a nozzle central axis 4C that is the central axis of spraying. In the case where “the injection nozzle 4 injects the additive from the nozzle tip 4N toward the upstream opening 3A”, the nozzle central axis 4C flows in the direction in which the exhaust gas G flows (the left-right direction in FIG. 1). Is not included. In the present embodiment, the nozzle center axis 4C has a shape extending from the upper right side toward the lower left side in FIG.

  Referring to FIG. 3, the additive 5 injected from the injection nozzle 4 evaporates gradually in the inner space of the enlarged diameter portion 3 immediately after being injected, and becomes substantially conical as it approaches the upstream opening 3A. Disperse to spread. In the present embodiment, when the additive 5 is vaporized and dispersed, the inner space of the enlarged diameter portion 3 is sufficiently utilized, and when the additive 5 reaches the vicinity of the upstream opening 3A, the additive 5 is It can spread so as to cover substantially the entire upstream opening 3A. Therefore, the exhaust gas G flowing in the exhaust pipe 1 and reaching the upstream opening 3A can contact the additive 5 widely dispersed in the vicinity of the upstream opening 3A, and contains sufficient additive 5. In this state, it becomes possible to flow to the catalyst 2C.

(First configuration example)
In the present embodiment, when a virtual extension line is drawn by extending the nozzle center axis 4C toward the upstream opening 3A side, the virtual extension line intersects the inner wall surface 1S of the exhaust pipe 1 and expands. It is comprised so that it may not cross | intersect the inner wall surface 3W of the diameter part 3 (refer FIG. 1). Although the said structure is not essential, by adopting the said structure, compared with the case where said virtual extension line cross | intersects the inner wall face 3W of the enlarged diameter part 3, the dispersibility of an additive is improved. This can be further improved.

(Second configuration example)
In the present embodiment, the injection nozzle 4 is configured so that the virtual extension line passes through a position P just at the center of the upstream opening 3A (see FIG. 1). Although the said structure is not essential, when the said structure is employ | adopted, compared with the case where it is comprised so that said virtual extension line may not pass through the position P, the dispersibility of an additive is improved more. It becomes possible.

(Third configuration example)
In the present embodiment, when a virtual extended surface is drawn by extending the conical side surface 4Q that defines the injection opening angle γ of the additive 5 injected conically from the injection nozzle 4, the virtual extended surface is the exhaust pipe. It intersects with the inner wall surface 1S of 1 and is configured not to intersect with the enlarged diameter portion 3 (see FIG. 1). The spray opening angle γ here means the spread angle of the spray formed by the additive 5 being injected from the nozzle tip 4N. In addition, since the particles in the additive 5 injected from the nozzle tip 4N fall slightly while drawing a parabola, the injection opening angle γ is a value immediately after the additive 5 comes out of the injection port of the nozzle tip 4N ( For example, it means the spread angle of the additive 5 at a position 10 mm away from the injection port of the nozzle tip 4N in the injection direction.

  The virtual extension surface of the conical side surface 4Q here is drawn by virtually extending the conical side surface 4Q that defines the injection opening angle γ of the additive 5 as described above, as shown in FIG. In such a sectional view, the virtual extension plane is represented by two-dot chain lines 4Q1 and 4Q2. In the present embodiment, these two-dot chain lines 4Q1 and 4Q2 intersect with a portion of the inner wall surface 1S located on the upstream side of the portion connected to the upstream opening 3A in the exhaust pipe 1. The configuration in which the virtual extension surface intersects with the inner wall surface 1S of the exhaust pipe 1 and does not intersect with the diameter-expanded portion 3 is not essential, but by adopting this configuration, the additive 5 is opened to the upstream side. It becomes possible to disperse at a higher density in the vicinity of the portion 3A.

(Fourth configuration example)
With reference to FIG. 1, here, the diameter of the inner wall surface 1S of the exhaust pipe 1 is defined as d. The maximum volume flow rate of the exhaust gas G flowing through the exhaust pipe 1 is defined as Q. The maximum volume flow rate Q is a value that is uniquely determined by the specifications of the internal combustion engine connected to the exhaust pipe 1 and is exhausted when the internal combustion engine is driven at the highest rotational speed under normal use conditions. The volume flow rate of the gas G. The inclination angle of the enlarged diameter portion 3 (inner wall surface 3W) with respect to the direction in which the exhaust pipe 1 extends is defined as α. An inclination angle of the nozzle central axis 4C of the injection nozzle 4 with respect to the inner wall surface 3W of the enlarged diameter portion 3 is defined as β. The elapsed time from the time when the additive 5 is injected from the injection nozzle 4 is defined as t. The time from when the additive 5 is injected from the injection nozzle 4 until the speed of the additive 5 becomes zero is defined as T.

Further, in a state where the exhaust gas G is not passed through the exhaust pipe 1 (a state of a constant volume container without a flow), the additive 5 at the time when the time t has elapsed since the additive 5 was injected from the injection nozzle 4. Is defined as U _s (t). In a state where the exhaust gas G is flowing through the exhaust pipe 1, the velocity of the additive 5 at the time when the time t has elapsed since the additive 5 was injected from the injection nozzle 4 is defined as U _x (t). In the direction in which the exhaust pipe 1 extends, the distance from the upstream opening 3A to an arbitrary location is defined as x. In the direction in which the exhaust pipe 1 extends, the distance from the upstream opening 3A to the nozzle tip 4N is defined as L.

The velocity U _x (t) is expressed by the following equation (1).

  The distance x is expressed by the following formula (2).

  The time T is expressed by the following formula (3).

  In the present embodiment, the time T and the distance L satisfy the following relationship (4).

  The configuration as described above is not essential, but by adopting the configuration, the distance L from the upstream opening 3A to the nozzle tip 4N can be optimized, and the additive 5 After vaporization, it is possible to disperse so that substantially the entire upstream opening 3A is sufficiently covered. The diameter d of the exhaust pipe 1 is preferably as small as possible within a range in which loss does not occur excessively so that the upstream opening 3A can be more sufficiently covered with the vaporized additive 5. The inclination angle β of the nozzle central axis 4C of the injection nozzle 4 with respect to the inner wall surface 3W of the enlarged diameter portion 3 is also distributed by the inner wall surface 3W of the enlarged diameter portion 3 by the additive 5 injected from the nozzle tip portion 4N of the injection nozzle 4. Is preferably set to an optimum value so as not to decrease.

[Comparative example]
FIG. 4 is a cross-sectional view showing the exhaust emission control device 11 in the comparative example. In the exhaust purification device 11, the injection nozzle 4 is disposed in the exhaust pipe 1, and the blade row 6 is provided in a portion immediately upstream of the upstream opening 3A. The injection nozzle 4 injects the additive 5 toward the blade row 6. The blade row 6 generates a swirling flow that flows around the tube axis of the exhaust pipe 1 and improves the dispersibility of the additive 5.

  The exhaust purification device 11 has a larger number of parts than the exhaust purification device 11 in the first embodiment by the number of members constituting the blade row 6. In addition, since the blade row 6 becomes resistant to the flow of the exhaust gas G, the blade row 6 can be an obstacle to improving fuel consumption. In the case where the blade row 6 is used, it may be difficult to improve the dispersibility of the additive 5 depending on the operating conditions. On the other hand, it can be said that the exhaust emission control device 10 in the above-described first embodiment can improve the dispersibility of the additive 5 with a simple configuration, that is, with a small number of parts.

[Embodiment 2]
With reference to FIG. 5 and FIG. 6, the exhaust emission control device 12 in the second embodiment will be described. FIG. 5 is a cross-sectional view showing the exhaust emission control device 12 (state of operation). FIG. 6 is a cross-sectional view taken along line VI-VI in FIG.

  The exhaust purification device 12 is different from the exhaust purification device 10 in the first embodiment in that the exhaust pipe 1 has a substantially rectangular cross-sectional shape. The substantially rectangular shape here is not limited to a rectangle (rectangle), but includes a square and a rectangle and a square having four rounded corners.

  When the exhaust pipe 1 having a substantially rectangular cross-sectional shape is used, man-hours are required for manufacturing the exhaust pipe 1 itself as compared with the case where the exhaust pipe 1 having a circular cross-sectional shape is used. The reached exhaust gas G can be uniformly contacted by the additive 5 widely dispersed in the vicinity of the upstream opening 3A, and can flow to the catalyst 2C in a state containing a sufficient additive 5. The configuration of the present embodiment can also be implemented in combination with any one or more of the first to third configuration examples in the first embodiment.

[Embodiment 3]
FIG. 7 is a cross-sectional view showing the exhaust purification device 13 according to the third embodiment. The exhaust purification device 13 is different from the exhaust purification device 10 in the first embodiment in the following points. That is, in the exhaust purification device 13, the inner wall surface 1S of the exhaust pipe 1 is positioned far from the nozzle tip portion 4N and is opposed to the nozzle tip portion 4N, and the nozzle tip than the facing portion 1M. A non-opposing portion 1N that is located near the portion 4N and does not face the nozzle tip 4N. That is, the inner wall surface 1S of the exhaust pipe 1 includes a facing portion 1M and a non-facing portion 1N, and the facing portion 1M is connected to the enlarged diameter portion 3 via the upstream opening 3A (3A2). The non-opposing portion 1N is connected to the enlarged diameter portion 3 through the upstream opening 3A (3A1). In the present embodiment, the facing portion 1M has a shape extending downstream from the non-facing portion 1N.

  When this configuration is adopted, the additive 5 injected from the injection nozzle 4 not only disperses in the vicinity of the upstream opening 3A but also contacts the facing portion 1M. The additive 5 that has come into contact with the facing portion 1M is folded back toward the central portion of the upstream opening 3A (the tube axis of the exhaust pipe 1) in the vicinity of the facing portion 1M and is further dispersed. The exhaust gas G that has reached the upstream opening 3A can come into contact with the additive 5 widely dispersed in the vicinity of the upstream opening 3A. The configuration of the present embodiment can also be implemented in combination with any one or more of the first to third configuration examples in the first embodiment. The configuration of the present embodiment can be implemented in combination with the second embodiment.

[Embodiment 4]
FIG. 8 is a cross-sectional view showing the exhaust emission control device 14 in the fourth embodiment. The exhaust purification device 14 is different from the exhaust purification device 10 in the first embodiment in the following points. That is, in the exhaust purification device 14, as in the case of the above-described third embodiment, the inner wall surface 1S of the exhaust pipe 1 is located far from the nozzle tip 4N and faces the nozzle tip 4N. A portion 1M and a non-opposing portion 1N that is located closer to the nozzle tip 4N than the facing portion 1M and does not face the nozzle tip 4N are included. That is, the inner wall surface 1S of the exhaust pipe 1 includes a facing portion 1M and a non-facing portion 1N, and the facing portion 1M is connected to the enlarged diameter portion 3 via the upstream opening 3A (3A2). The non-opposing portion 1N is connected to the enlarged diameter portion 3 through the upstream opening 3A (3A1). In the present embodiment, the opposing portion 1M is provided with a recess 1F having a shape that is recessed toward the direction away from the injection nozzle 4.

  When this configuration is adopted, the additive 5 injected from the injection nozzle 4 not only disperses in the vicinity of the upstream opening 3A but also contacts the recess 1F of the facing portion 1M. The additive 5 that has come into contact with the recess 1F is folded back toward the central portion of the upstream opening 3A (the tube axis of the exhaust pipe 1) in the vicinity of the recess 1F, and is further widely dispersed. The exhaust gas G that has reached the upstream opening 3A can come into contact with the additive 5 widely dispersed in the vicinity of the upstream opening 3A. The configuration of the present embodiment can also be implemented in combination with any one or more of the first to third configuration examples in the first embodiment. The configuration of the present embodiment can be implemented in combination with the second embodiment.

  Although the embodiment has been described above, the above disclosure is illustrative in all respects and is not restrictive. The technical scope of the present invention is defined by the terms of the claims, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.

  DESCRIPTION OF SYMBOLS 1 Exhaust pipe, 1F recessed part, 1M opposing part, 1N non-opposing part, 1S, 3W inner wall surface, 2 catalyst accommodating chamber, 2C catalyst, 3 diameter expansion part, 3A upstream opening part, 3B downstream opening part, 4 injection nozzle 4C Nozzle central axis, 4N Nozzle tip, 4Q1, 4Q2 Double-dot chain line, 4Q Conical side surface, 5 Additive, 6 Blade row, 10, 11, 12, 13, 14 Exhaust gas purification device, G exhaust gas.

Claims (8)

An exhaust pipe through which exhaust gas flows inside the inner wall;
A catalyst housing chamber having a flow passage cross-sectional area larger than the flow passage cross-sectional area of the exhaust pipe, provided downstream of the exhaust pipe, and having a catalyst disposed inside;
Including an upstream opening and a downstream opening, wherein the upstream opening is connected to the exhaust pipe, the downstream opening is connected to the catalyst housing chamber, and the downstream opening is connected to the downstream opening. A diameter-enlarged portion for allowing the exhaust gas from the exhaust pipe to flow into the catalyst housing chamber, having a shape in which the flow path cross-sectional area gradually increases as it goes to
An injection nozzle that has a nozzle tip disposed so as to be exposed in the inner space of the diameter-enlarged portion, and injects the additive from the nozzle tip toward the upstream opening,
Exhaust purification device. The spray nozzle has a nozzle central axis;
When a virtual extension line is drawn by extending the nozzle central axis toward the upstream opening, the virtual extension line intersects with the inner wall surface of the exhaust pipe and intersects with the enlarged diameter part. do not do,
The exhaust emission control device according to claim 1. The injection nozzle is configured such that the virtual extension line passes through a position just at the center of the upstream opening,
The exhaust emission control device according to claim 2. When a virtual extended surface is drawn by extending a conical side surface that defines an injection opening angle of the additive sprayed conically from the injection nozzle, the virtual extended surface intersects the inner wall surface of the exhaust pipe. , Do not intersect with the enlarged diameter part,
The exhaust emission control device according to claim 2 or 3. A diameter d of the inner wall surface of the exhaust pipe;
A maximum volume flow rate Q of the exhaust gas flowing through the exhaust pipe;
An inclination angle α of the enlarged diameter portion with respect to a direction in which the exhaust pipe extends,
An inclination angle β of the nozzle central axis with respect to the enlarged diameter portion,
Elapsed time t from the time when the additive is jetted from the jet nozzle,
A time T from when the additive is sprayed from the spray nozzle until the speed of the additive becomes zero, T
In a state where the exhaust gas is not passed through the exhaust pipe, the speed U _s (t) of the additive at the time when time t has elapsed since the additive was injected from the injection nozzle,
In the state where the exhaust gas is flowing through the exhaust pipe, the additive velocity U _x (t) at the time when time t has elapsed since the additive was injected from the injection nozzle,
In the direction in which the exhaust pipe extends, a distance x from the upstream opening to an arbitrary location, and
When the distance L from the upstream opening to the nozzle tip is used in the direction in which the exhaust pipe extends,
The speed U _x (t) is represented by the following equation (1):

The distance x is represented by the following formula (2):

The time T is represented by the following formula (3):

The time T and the distance L satisfy the relationship of the following formula (4).

The exhaust emission control device according to claim 4. The exhaust pipe has a substantially rectangular cross-sectional shape,
The exhaust emission control device according to any one of claims 1 to 4. The inner wall surface of the exhaust pipe is
A facing portion located far from the nozzle tip and facing the nozzle tip;
A non-opposing portion that is located closer to the nozzle tip than the facing portion and does not face the nozzle tip,
The facing portion has a shape extending downstream from the non-facing portion,
The exhaust emission control device according to any one of claims 1 to 4. The inner wall surface of the exhaust pipe is
A facing portion located far from the nozzle tip and facing the nozzle tip;
A non-opposing portion that is located closer to the nozzle tip than the facing portion and does not face the nozzle tip,
The opposed portion is provided with a recess having a shape that is recessed in a direction away from the injection nozzle.
The exhaust emission control device according to any one of claims 1 to 4.

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