JP2010275930A - Exhaust gas passage structure for internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide technology for efficiently supplying additive to a small sized catalyst from an addition valve, while avoiding soot from accumulating around the addition valve, in an exhaust gas passage structure for an internal combustion engine. <P>SOLUTION: A small-sized catalyst 3 disposed separately from an inner wall surface of an exhaust gas passage 2, an addition valve passage 4 disposed at an outside of the exhaust gas passage 2 and opening to an inside of the exhaust gas passage 2, a fuel addition valve 5 disposed in the addition valve passage 4 and adding fuel to the small sized catalyst 3, and a tubular member 6 hollow in an exhaust gas flow direction connected to an exhaust gas flow direction of the small sized catalyst 3, are included in the exhaust gas passage 2 for an internal combustion engine. A fuel inlet section 7, which is a hole for introducing fuel added from the fuel addition valve 5 into the tubular member 6 is disposed at a part of the tubular member 6, crossing an addition orientation direction of fuel added initially from the fuel addition valve 5 in the addition valve passage 4. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to an exhaust passage structure of an internal combustion engine in which an additive is added to a small catalyst from an addition valve.

  A technique is disclosed that includes a fuel addition valve for adding fuel to the upstream side in the exhaust flow direction of the NOx storage reduction catalyst disposed in the exhaust passage of the internal combustion engine (see, for example, Patent Document 1). In this technique, by adding fuel to the exhaust gas upstream of the NOx storage reduction catalyst, the air-fuel ratio of the exhaust gas flowing into the NOx storage reduction catalyst is lowered compared to that during normal operation, so-called NOx reduction control. And SOx poisoning recovery control.

JP 2008-231926 A

  By the way, as a catalyst arrange | positioned in the exhaust passage of an internal combustion engine, the small catalyst spaced apart from the inner wall face of an exhaust passage may be used. In this case, it is difficult to efficiently supply the additive to the small catalyst. As a solution, it is conceivable to bring an addition valve for adding an additive close to the small catalyst. However, if the addition valve is too close to the small catalyst, soot may accumulate around the addition valve.

  The present invention has been made in view of the above problems, and an object of the present invention is to efficiently reduce the size of the additive from the addition valve while avoiding soot accumulation around the addition valve in the exhaust passage structure of the internal combustion engine. The object is to provide a technology for supplying the catalyst.

In the present invention, the following configuration is adopted. That is, the present invention
A small catalyst disposed in the exhaust passage of the internal combustion engine and spaced from the inner wall surface of the exhaust passage;
An addition valve passage provided outside the exhaust passage and opening into the exhaust passage;
An addition valve disposed in the addition valve passage for adding an additive to the small catalyst;
An internal hollow tubular member connected in the exhaust flow direction upstream of the small catalyst in the exhaust flow direction;
With
Additive introduction for introducing the additive added from the addition valve into the tubular member at the portion of the tubular member that first intersects the direction of addition of the additive added from the addition valve in the addition valve passage. An exhaust passage structure for an internal combustion engine, characterized in that a portion is provided.

  According to the present invention, the additive added from the addition valve in the addition valve passage can be introduced into the tubular member via the additive introduction part of the tubular member. In the tubular member, the additive is hardly leaked outside and is guided to the upstream end of the small catalyst in the exhaust flow direction. Thereby, an additive can be efficiently supplied to a small catalyst.

  On the other hand, the addition valve is provided in an addition valve passage provided outside the exhaust passage, and the addition valve is separated from the small catalyst. Thereby, it is possible to avoid soot accumulation around the addition valve due to the addition valve being too close to the small catalyst.

  A holding member for holding the small catalyst and the tubular member in the exhaust passage, wherein the holding member is provided in an opening of the addition valve passage in a space where the opening of the addition valve passage and the additive introduction portion face each other; It may be arranged so as to avoid the maximum width region orthogonal to the exhaust flow direction. A holding member that holds the small catalyst and the tubular member in the exhaust passage; and the holding member fixes the tubular member or the small catalyst downstream in the exhaust flow direction from the additive introduction portion. Good.

  According to the present invention, it is possible to prevent the exhaust gas flowing from the additive introduction part to the addition valve passage side from being guided to the addition valve passage by the holding member and flowing into the addition valve passage. Thereby, it is possible to avoid the accumulation of soot around the addition valve due to the exhaust gas flowing from the additive introduction part to the addition valve passage side flowing into the addition valve passage.

  It is preferable to provide an airflow adjusting plate on the upstream side in the exhaust flow direction of the additive introduction portion, the downstream side in the exhaust flow direction being closer to the addition valve passage than the upstream side in the exhaust flow direction.

  According to the present invention, the flow of exhaust gas flowing from the periphery of the additive introduction portion to the small catalyst on the side of the addition valve passage and the inner wall surface of the exhaust passage can be smoothed by the air flow adjusting plate. Therefore, it is possible to weaken the flow of the exhaust gas flowing from the additive introduction part to the addition valve passage side generated by the increase in the exhaust pressure loss of the exhaust passage due to the arrangement of the small catalyst, and the exhaust gas is supplied to the addition valve passage. It is possible to suppress the inflow. Thereby, it is possible to suppress the accumulation of soot around the addition valve due to the exhaust gas flowing from the additive introduction part to the addition valve passage side flowing into the addition valve passage.

  Exhaust gas flowing from the additive introduction part to the addition valve passage side is connected to the addition valve passage side with respect to the downstream end in the exhaust flow direction at the opening of the addition valve passage. It is good to set to the downstream in the exhaust flow direction with a predetermined distance not to flow into the passage.

  Here, the predetermined distance is a distance that prevents the exhaust gas flowing from the additive introduction part to the addition valve passage side from flowing into the addition valve passage, and is obtained in advance through experiments, verifications, and the like.

  According to the present invention, it is possible to prevent the exhaust gas flowing from the additive introduction part to the addition valve passage side from flowing into the addition valve passage. Thereby, it is possible to avoid the accumulation of soot around the addition valve due to the exhaust gas flowing from the additive introduction part to the addition valve passage side flowing into the addition valve passage.

  According to the present invention, in the exhaust passage structure of an internal combustion engine, the additive can be efficiently supplied to the small catalyst from the addition valve while avoiding soot accumulation around the addition valve.

1 is a diagram illustrating a schematic configuration of an internal combustion engine and an exhaust system thereof according to a first embodiment. 1 is a diagram illustrating a schematic configuration of an exhaust passage structure according to Embodiment 1. FIG. 1 is a perspective view showing a tubular member according to Example 1. FIG. It is a figure which shows the case where the exhaust_gas | exhaustion which distribute | circulates to the addition valve channel | path side from a fuel introduction part flows in into an addition valve channel | path. 6 is a diagram illustrating a schematic configuration of a holding member as viewed from the upstream side in the exhaust flow direction according to Configuration Example 1 of Embodiment 2. FIG. 6 is a diagram illustrating a schematic configuration of a holding member as viewed from the upstream side in the exhaust flow direction according to Configuration Example 2 of Embodiment 2. FIG. 6 is a diagram illustrating a schematic configuration of a holding member according to Configuration Example 3 of Embodiment 2. FIG. 6 is a diagram illustrating a schematic configuration of a holding member as viewed from the upstream side in the exhaust flow direction according to Configuration Example 4 of Embodiment 2. FIG. 10 is a diagram illustrating a schematic configuration of a holding member according to Configuration Example 5 of Embodiment 2. FIG. 10 is a diagram illustrating a schematic configuration of a holding member according to Configuration Example 6 of Embodiment 2. FIG. It is a figure which shows schematic structure of the holding member seen from upper direction concerning the structural example 7 of Example 2. FIG. It is a figure which shows schematic structure of the holding member seen from the exhaust flow direction upstream which concerns on the structural example 7 of Example 2. FIG. FIG. 6 is a diagram illustrating a schematic configuration of an exhaust passage structure according to a third embodiment. FIG. 6 is a diagram illustrating a schematic configuration of an exhaust passage structure according to a fourth embodiment.

  Specific examples of the present invention will be described below.

<Example 1>
FIG. 1 shows a schematic configuration of an internal combustion engine to which the exhaust passage structure of the internal combustion engine according to this embodiment is applied and its exhaust system. FIG. 2 shows a schematic configuration of the exhaust passage structure according to the present embodiment. An internal combustion engine 1 shown in FIG. 1 is a water-cooled four-stroke cycle diesel engine having four cylinders. The internal combustion engine 1 is mounted on a vehicle. In this embodiment, a diesel engine will be described as an example, but the present invention can be applied to other engines such as a gasoline engine.

  An exhaust passage 2 is connected to the internal combustion engine 1. A small catalyst 3 is disposed in the exhaust passage 2. The small catalyst 3 is separated from the inner wall surface of the exhaust passage 2. That is, the outer diameter of the cylindrical small catalyst 3 is smaller than the diameter of the inner wall surface of the exhaust passage 2. For this reason, the exhaust gas flows between the small catalyst 3 and the inner wall surface of the exhaust passage 2 (side the small catalyst 3).

  The small catalyst 3 has an oxidation function, and is supplied with a reducing agent such as fuel as an additive to the small catalyst 3 to raise the temperature of the exhaust gas or reform the exhaust gas. In addition, the small catalyst 3 may be supplied with an additive so as to exhibit other functions. For this reason, although the example which uses the fuel which is a reducing agent is given in a present Example, as an additive of this invention, it is not restricted to this.

  An addition valve passage 4 that opens into the exhaust passage 2 is attached to the outside of the exhaust passage 2 upstream of the small catalyst 3 in the exhaust flow direction. A fuel addition valve 5 for adding fuel to the small catalyst 3 is disposed in the addition valve passage 4. The fuel added from the fuel addition valve 5 is supplied to the small catalyst 3. Note that the inner diameter of the addition valve passage 4 is a size that does not hinder the direction of fuel addition directed from the fuel addition valve 5. The fuel addition valve 5 of this embodiment corresponds to the addition valve of the present invention.

  On the upstream side of the small catalyst 3 in the exhaust flow direction, an internal hollow tubular member 6 is connected adjacently in the exhaust flow direction. The outer diameter of the tubular member 6 is the same as the outer diameter of the small catalyst 3. The tubular member 6 is provided in a region that covers the addition direction of fuel added from the fuel addition valve 5 in the addition valve passage 4.

As shown in FIG. 3, the tubular member 6 has a fuel introduction portion 7 at a portion that first intersects with the addition direction of the fuel added from the fuel addition valve 5 in the addition valve passage 4. The fuel introduction part 7 is formed with a hole, and the fuel added from the fuel addition valve 5 can be introduced into the tubular member 6. Further, the tubular member 6 receives the fuel added from the fuel addition valve 5 at the portion that intersects in the direction of the addition of the fuel added from the fuel addition valve 5 in the addition valve passage 4 at the bottom in the figure. Therefore, the fuel can be retained in the tubular member 6. In the tubular member 6, the fuel hardly leaks outside, and the fuel is guided to the upstream end of the small catalyst 3 in the exhaust flow direction. Thereby, the fuel can be efficiently supplied to the small catalyst 3. The fuel introduction unit 7 may have a wider range than the addition directing direction in consideration of a change in the addition directing direction of the fuel added from the fuel addition valve 5. The fuel introduction part 7 of this embodiment corresponds to the additive introduction part of the present invention. In addition, the fuel introduction part 7 should just be a shape which can introduce | transduce the fuel added from the fuel addition valve 5 in the tubular member 6, The shape is not limited to a hole.

  The exhaust passage 2 and the devices arranged in the exhaust passage 2 constitute an exhaust system of the internal combustion engine 1.

  The internal combustion engine 1 configured as described above is provided with an ECU 8 that is an electronic control unit for controlling the internal combustion engine 1. The ECU 8 is a unit that controls the operation state of the internal combustion engine 1 in accordance with the operation conditions of the internal combustion engine 1 and the request of the driver. The ECU 8 is connected to an accelerator opening sensor 9 that outputs an electric signal corresponding to the amount of depression of the accelerator pedal, and a crank position sensor 10 that detects the engine speed of the internal combustion engine 1 via electric wiring. Is output to the ECU 8. On the other hand, the fuel addition valve 5 is connected to the ECU 8 via an electrical wiring, and the fuel addition valve 5 is controlled by the ECU 8 to instruct the added fuel amount, the addition timing, and the like.

  According to the present embodiment described above, the fuel added from the fuel addition valve 5 in the addition valve passage 4 can be introduced into the tubular member 6 via the fuel introduction portion 7 of the tubular member 6. In the tubular member 6, the fuel hardly leaks out of the tubular member 6, and the fuel is guided to the upstream end of the small catalyst 3 in the exhaust flow direction. Thereby, the fuel can be efficiently supplied to the small catalyst 3.

  On the other hand, the fuel addition valve 5 is provided in an addition valve passage 4 provided outside the exhaust passage 2, and the fuel addition valve 5 is separated from the small catalyst 3. Thereby, it is possible to avoid soot accumulation around the fuel addition valve 5 due to the fuel addition valve 5 being too close to the small catalyst 3.

  Therefore, according to this embodiment, fuel can be efficiently supplied from the fuel addition valve 5 to the small catalyst 3 while avoiding soot accumulation around the fuel addition valve 5.

<Example 2>
Next, Example 2 will be described. In the present embodiment, a holding member that holds the small catalyst 3 and the tubular member 6 described in the above embodiment in the exhaust passage 2 will be described. In the present embodiment, the characteristic portion will be described, and the description of the other portions described in the above embodiment will be omitted.

  Since the small catalyst 3 and the tubular member 6 are arranged apart from the inner wall surface of the exhaust passage 2, the small catalyst 3 and the tubular member 6 are separated from the inner wall surface of the exhaust passage 2 from the small catalyst 3 and the tubular member 6. It is necessary to provide a holding member that holds

  However, as shown in FIG. 4, depending on the arrangement position of the holding member, the exhaust C1 flowing from the fuel introduction portion 7 indicated by the arrow to the addition valve passage 4 side is guided to the addition valve passage 4 by the holding member and added. There is a risk of flowing into the valve passage 4. If so, there is a possibility that soot accumulates around the fuel addition valve 5 due to the exhaust gas flowing from the fuel introduction portion 7 to the addition valve passage 4 flowing into the addition valve passage 4.

Therefore, in the present embodiment, as shown in FIGS. 5 and 6, the holding member 11 has the opening of the addition valve passage 4 in the space of the exhaust passage 2 where the opening of the addition valve passage 4 and the fuel introduction portion 7 face each other. It is arranged so as to avoid the maximum width region orthogonal to the exhaust flow direction. Alternatively, the holding member 11 is placed in the space.
7, as shown in FIG. 7, the holding member 11 fixes the tubular member 6 downstream of the fuel introduction portion 7 in the exhaust flow direction.

  In the configuration example 1 of FIG. 5, the holding member 11 avoids the upper space S <b> 1 of the small catalyst 3 where the opening of the addition valve passage 4 and the fuel introduction part 7 face each other, and the holding member 11 One is arranged. The holding member 11 is a plate member, and the plane of the plate member is disposed in parallel with the exhaust flow direction so as not to change the flow of exhaust, and the inner wall surface of the exhaust passage 2 and the tubular member 6 are parallel to the exhaust flow direction. Welded.

  In the configuration example 2 of FIG. 6, the holding member 11 has a maximum width orthogonal to the exhaust flow direction of the opening of the addition valve passage 4 in the space of the exhaust passage 2 where the opening of the addition valve passage 4 and the fuel introduction portion 7 face each other. The three are arranged in the left and right side spaces and the lower space of the small catalyst 3 so as to avoid the region S2. The holding member 11 is a plate member similar to the configuration example 1 of FIG.

  In the configuration example 3 of FIG. 7, the holding member 11 is disposed in the upper space of the small catalyst 3 where the opening of the addition valve passage 4 and the fuel introduction portion 7 face each other, but the exhaust introduction flow direction downstream side of the fuel introduction portion 7. The tubular member 6 is fixed downstream of the end 7a in the exhaust flow direction. The position of the holding member 11 attached to the inner wall surface of the exhaust passage 2 is on the downstream side in the exhaust flow direction from the position where the tubular member 6 is fixed. The holding member 11 is a plate member similar to the configuration example 1 of FIG. As shown in FIG. 7, the method of fixing the tubular member 6 on the downstream side in the exhaust flow direction of the holding member 11 with respect to the fuel introduction portion 7 is performed in conjunction with the structure of the holding member 11 shown in FIGS. May be. Further, the holding member 11 shown in FIG. 7 may fix the small catalyst 3 downstream of the tubular member 6 in the exhaust flow direction instead of the tubular member 6. Furthermore, you may further provide holding members other than the holding member 11 shown in FIG.

  According to the present embodiment described above, the exhaust gas flowing from the fuel introduction portion 7 to the addition valve passage 4 side is prevented from being guided to the addition valve passage 4 by the holding member 11 and flowing into the addition valve passage 4. can do. As a result, it is possible to avoid the accumulation of soot around the fuel addition valve 5 due to the exhaust flowing from the fuel introduction part 7 to the addition valve passage 4 flowing into the addition valve passage 4.

  Here, another structure of the holding member 11 will be described.

  In the configuration example 4 in FIG. 8, when the holding member 11 cannot be welded to the tubular member 6, the small catalyst 3 and the tubular member are arranged at the center of the three holding members 11 by tension of the holding member 11 that is a plate member. 6 is arranged. The arrangement position and the like of the holding member 11 are the same as in the configuration example 2 in FIG.

  9 includes a first attachment portion 11a attached to the tubular member 6 and a second attachment portion 11b attached to the inner wall surface of the exhaust passage 2, and the first and second attachment portions 11a. 11b are connected by welding or the like. 9 shows a case where the arrangement position of the holding member 11 is the same as that of the configuration example 3 of FIG. 7, but the arrangement position of the holding member 11 is the same as that of the configuration example 1 of FIG. 5 or FIG. You may apply in the case of the structural example 2.

  In the configuration example 6 of FIG. 10, the exhaust passage 2 is divided at the side of the addition valve passage 4 and the downstream side thereof at the time of manufacture as shown by the broken line D1 in the drawing. The exhaust passage 2 is divided into the tubular member 6. The attached holding member 11 is sandwiched and fixed. 10 shows a case where the arrangement position of the holding member 11 is the same as that of the configuration example 3 of FIG. 7, but the arrangement position of the holding member 11 is the same as that of the configuration example 1 of FIG. You may apply in the case of the structural example 2.

In the structural example 7 of FIG.11 and FIG.12, as shown in FIG.
The small catalyst 3 has a length in the exhaust flow direction excluding the fuel introduction part 7 of the small catalyst 3 and the tubular member 6, and the opening of the addition valve passage 4 and the fuel introduction part 7 face each other as shown in FIG. The four small catalyst 3 are arranged at the upper right, lower right, upper left, and lower left, avoiding the maximum width region S2 orthogonal to the exhaust flow direction of the opening of the addition valve passage 4. The holding member 11 is a plate member, and the plane of the plate member is arranged in parallel with the exhaust flow direction so as not to change the flow of exhaust. The holding member 11 is a welded portion 11c having a welded area provided at the inner wall surface of the exhaust passage 2 and the end portion contacting the tubular member 6, and the inner wall surface of the exhaust passage 2 and the tubular member parallel to the exhaust flow direction. 6 and welded.

  The holding member 11 having the above structure may be used. Moreover, you may use the holding member 11 of another structure other than that. The holding member 11 only needs to be configured so that the exhaust gas flowing beside the small catalyst 3 and the tubular member 6 is not bent toward the addition valve passage 4. Further, in the present embodiment, the holding member 11 provided at the holding position on the upstream side of the exhaust flow of the small catalyst 3 and the tubular member 6 has been described. Similarly, the holding member 11 on the downstream side of the exhaust flow of the small catalyst 3 is also described. A holding member 11 is provided.

<Example 3>
Next, Example 3 will be described. In the present embodiment, an airflow adjusting plate provided on the tubular member 6 described in the above embodiment will be described. In the present embodiment, the characteristic portion will be described, and the description of the other portions described in the above embodiment will be omitted.

  Due to the increase in the exhaust pressure loss in the exhaust passage 2 caused by the arrangement of the small catalyst 3, there is a risk that turbulent flow may occur and an exhaust flow flowing from the fuel introduction part 7 to the addition valve passage 4 side may be generated. If so, there is a possibility that soot accumulates around the fuel addition valve 5 due to the exhaust gas flowing from the fuel introduction portion 7 to the addition valve passage 4 flowing into the addition valve passage 4.

  Therefore, in the present embodiment, as shown in FIG. 13, the airflow in which the downstream side in the exhaust flow direction is closer to the addition valve passage 4 than the upstream side in the exhaust flow direction on the upstream side in the exhaust flow direction of the fuel introduction portion 7 in the tubular member 6. An adjustment plate 12 is provided. The airflow adjustment plate 12 has an angle θ that is obtained in advance through experiments and verifications such that the upstream side in the exhaust flow direction to the downstream side in the exhaust flow direction is horizontal or less than a right angle, and the downstream end of the airflow adjustment plate 12 in the exhaust flow direction. Is the upstream side in the exhaust gas flow direction from the downstream end of the fuel introduction part 7 in the exhaust gas flow direction.

  According to the present embodiment, as indicated by the arrow in FIG. 13, the exhaust gas C <b> 2 flowing between the small catalyst 3 on the addition valve passage 4 side and the inner wall surface of the exhaust passage 2 from the vicinity of the fuel introduction portion 7 by the air flow adjusting plate 12. Can be smoothed. That is, the airflow adjusting plate 12 makes it difficult for turbulent flow due to an increase in exhaust pressure loss in the exhaust passage 2 due to the arrangement of the small catalyst 3. Therefore, the flow of the exhaust gas (corresponding to C1 in FIG. 4) flowing from the fuel introduction portion 7 to the addition valve passage 4 side generated by the increase in the exhaust pressure loss of the exhaust passage 2 due to the placement of the small catalyst 3 is obtained. It can weaken and it can control that the exhaust concerned flows into addition valve passage 4. Thereby, it is possible to suppress the accumulation of soot around the fuel addition valve 5 due to the exhaust gas flowing from the fuel introduction part 7 to the addition valve passage 4 flowing into the addition valve passage 4.

  In addition, since the present Example differs in the characteristic part from the said Example, you may combine it in any way with the said Example.

<Example 4>
Next, Example 4 will be described. In the present embodiment, setting of the arrangement positions of the small catalyst 3 and the tubular member 6 and the addition valve passage 4 described in the above embodiment will be described. In the present embodiment, the characteristic portion will be described, and the description of the other portions described in the above embodiment will be omitted.

  Even in the configuration shown in FIG. 2 of the first embodiment, as shown in FIG. 4, the exhaust C <b> 1 flowing from the fuel introduction portion 7 to the addition valve passage 4 side may flow into the addition valve passage 4. . If so, there is a possibility that soot accumulates around the fuel addition valve 5 due to the exhaust gas flowing from the fuel introduction portion 7 to the addition valve passage 4 flowing into the addition valve passage 4.

  Therefore, in this embodiment, as shown in FIG. 14, the downstream end 7 a in the exhaust flow direction in the fuel introduction portion 7 is set to the downstream end 4 a in the exhaust flow direction in the opening of the addition valve passage 4. Is set downstream of the exhaust flow direction with a predetermined distance L1 at which the exhaust gas flowing from the exhaust gas to the addition valve passage 4 side does not flow into the addition valve passage 4.

  Here, the predetermined distance L1 is a distance that prevents the exhaust gas flowing from the fuel introduction portion 7 to the addition valve passage 4 side from flowing into the addition valve passage 4, and is obtained in advance by experiments, verifications, and the like.

  According to this embodiment, since the predetermined distance L1 is set, it is possible to prevent the exhaust gas flowing from the fuel introduction part 7 to the addition valve passage 4 side from flowing into the addition valve passage 4. As a result, it is possible to avoid the accumulation of soot around the fuel addition valve 5 due to the exhaust flowing from the fuel introduction part 7 to the addition valve passage 4 flowing into the addition valve passage 4.

  In addition, since the present Example differs in the characteristic part from the said Example, you may combine it in any way with the said Example.

  The exhaust passage structure of the internal combustion engine according to the present invention is not limited to the above-described embodiments, and various modifications may be made without departing from the scope of the present invention.

DESCRIPTION OF SYMBOLS 1 Internal combustion engine 2 Exhaust passage 3 Small catalyst 4 Addition valve passage 4a Exhaust flow direction downstream end 5 of addition valve passage 5 Fuel addition valve 6 Tubular member 7 Fuel introduction part 7a Exhaust flow direction downstream end 8 of fuel introduction part ECU
9 Accelerator opening sensor 10 Crank position sensor 11 Holding member 11a First attachment portion 11b Second attachment portion 11c Welding portion 12 Airflow adjustment plate

Claims (5)

A small catalyst disposed in the exhaust passage of the internal combustion engine and spaced from the inner wall surface of the exhaust passage;
An addition valve passage provided outside the exhaust passage and opening into the exhaust passage;
An addition valve disposed in the addition valve passage for adding an additive to the small catalyst;
An internal hollow tubular member connected in the exhaust flow direction upstream of the small catalyst in the exhaust flow direction;
With
Additive introduction for introducing the additive added from the addition valve into the tubular member at the portion of the tubular member that first intersects the direction of addition of the additive added from the addition valve in the addition valve passage. An exhaust passage structure for an internal combustion engine, characterized in that a portion is provided. A holding member for holding the small catalyst and the tubular member in the exhaust passage;
The holding member is disposed so as to avoid a region having a maximum width perpendicular to the exhaust flow direction of the opening of the addition valve passage in a space where the opening of the addition valve passage and the additive introduction portion face each other. The exhaust passage structure for an internal combustion engine according to claim 1. A holding member for holding the small catalyst and the tubular member in the exhaust passage;
The exhaust passage structure for an internal combustion engine according to claim 1 or 2, wherein the holding member fixes the tubular member or the small catalyst downstream of the additive introduction portion in the exhaust flow direction.   4. The air flow adjusting plate according to claim 1, further comprising an airflow adjusting plate on the upstream side in the exhaust flow direction of the additive introduction portion, the airflow adjustment plate being closer to the addition valve passage than the upstream side in the exhaust flow direction. 2. An exhaust passage structure for an internal combustion engine according to item 1.   Exhaust gas flowing from the additive introduction part to the addition valve passage side is connected to the addition valve passage side with respect to the downstream end in the exhaust flow direction at the opening of the addition valve passage. The exhaust passage structure for an internal combustion engine according to any one of claims 1 to 4, wherein the exhaust passage structure is set on the downstream side in the exhaust flow direction with a predetermined distance not to flow into the passage.

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