JP2009036150A - Reducing agent addition device for internal combustion engine - Google Patents

Abstract

In a reducing agent addition device that is provided in an exhaust passage of an internal combustion engine and adds a reducing agent to exhaust passing through the exhaust passage, the reducing agent injected from the reducing agent injection valve is more dispersed in the exhaust. Provide technology that can.
Assist exhaust exhaust introduced into a gap portion 25 via an exhaust introduction pipe 29 is guided to a fuel spray region AHC while being rotated along an inner peripheral surface of an outer housing 24 to promote atomization of the fuel. Then, by passing the catalyst 27 through the fuel and the assist exhaust, the lightening of the fuel is promoted. Further, when the fuel and the assist exhaust whose atomization and lightening are promoted are passed through the through holes 28a formed in the perforated plate 28, the distribution area in the orthogonal cross section is increased, and then the fuel is exhausted together with the assist exhaust and the exhaust pipe. 11 is introduced.
[Selection] Figure 2

Description

The present invention relates to a reducing agent addition device that adds a reducing agent to exhaust gas that passes through an exhaust passage of an internal combustion engine.

  An exhaust purification device is provided in the exhaust passage of the internal combustion engine for the purpose of removing harmful substances contained in the exhaust discharged from the internal combustion engine and purifying the exhaust. Examples of the exhaust purification device include a storage reduction type NOx catalyst that purifies NOx in exhaust gas and a selective reduction type NOx catalyst (hereinafter collectively referred to as “NOx catalyst”).

The NOx storage reduction catalyst stores nitrogen oxides (NOx) in the exhaust when the oxygen concentration in the exhaust gas flowing in is high, and absorbs the oxygen concentration in the exhaust gas when the oxygen concentration in the exhaust gas decreases and a reducing agent is present. It is a catalyst for reducing nitrogen oxide (NOx) to nitrogen (N ₂ ). Selective reduction type N
The Ox catalyst is a catalyst that reduces nitrogen oxide (NOx) when a reducing agent is present in an oxygen-excess atmosphere. Since these NOx catalysts can purify NOx in exhaust gas in the presence of a reducing agent, it is necessary to supply the reducing agent to the NOx catalyst in order to purify NOx.

  One method of supplying a reducing agent to a NOx catalyst as an exhaust purification device is to provide a reducing agent addition device in the exhaust passage upstream of the exhaust purification device, and the addition of the reducing agent to the exhaust by the reducing agent addition device. Can be mentioned. Here, in order for the reducing agent to react efficiently in the exhaust gas purification apparatus, it is necessary to further disperse the reducing agent added to the exhaust gas in the exhaust gas.

In relation to this, in the reducing agent addition device described in Patent Document 1, the injection nozzle for injecting the reducing agent has a spiral element that forms a spiral air flow, and the reduction is carried on the air flow. By spraying the agent, the atomization of the reducing agent is promoted.
Japanese Patent No. 2559620 JP 2001-173431 A Japanese Patent Laid-Open No. 2004-3400 Japanese Patent Laid-Open No. 2000-282843

  However, as in the prior art disclosed in Patent Document 1, there is a case where the dispersion of the reducing agent into the exhaust gas is insufficient when the reducing agent is simply injected (added) on a spiral air flow.

  The present invention has been made in view of the above prior art, and an object thereof is to provide a reducing agent addition device that is provided in an exhaust passage of an internal combustion engine and adds a reducing agent to exhaust gas that passes through the exhaust passage. Another object of the present invention is to provide a technique capable of further dispersing the reducing agent injected from the reducing agent injection valve in the exhaust gas.

In order to achieve the above object, an exhaust gas purification system for an internal combustion engine according to the present invention employs the following means.
That is, a reducing agent addition device for adding a reducing agent to exhaust gas passing through an exhaust passage of an internal combustion engine,
A reducing agent injection valve for injecting the reducing agent;
A part of the exhaust gas passing through the exhaust passage is led to a spray region of the reducing agent injected by the reducing agent injection valve via a path different from the exhaust passage to promote atomization of the reducing agent, and the different Fine particulate reducing agent introduction means for introducing exhaust and reducing agent through the passage into the exhaust passage;
A reducing agent reforming catalyst that promotes lightening of the reducing agent before the reducing agent mixed with the exhaust via the different path is introduced into the exhaust passage;
A distribution region increasing means for increasing a region where the reducing agent is distributed after the reducing agent passes through the reducing agent reforming catalyst or when passing through the reducing agent reforming catalyst;
It is characterized by providing.

  That is, in the present invention, before the reducing agent injected from the reducing agent injection valve is introduced into the exhaust passage, a part of the exhaust gas passing through the exhaust passage is reduced via a route different from the exhaust passage. It was decided to lead to the spray area of the agent. Here, for the sake of convenience, the different paths are referred to as “exhaust introduction paths”, and the exhaust gas that is guided to the spray region of the reducing agent via the exhaust introduction paths is referred to as “assist exhaust”.

  When the assist exhaust gas is guided to the reducing agent spray region, the assist exhaust particles and the reducing agent particles collide with each other. As a result, since the particle diameter of the reducing agent becomes finer, atomization of the reducing agent is promoted. Thus, by introducing the atomized reducing agent into the exhaust passage, the dispersibility of the reducing agent can be improved.

  In the present invention, the reducing agent atomized by colliding with the assist exhaust gas is reduced by passing the reducing agent reforming catalyst through the reducing agent before the reducing agent is introduced into the exhaust passage by the particulate reducing agent introduction means. It was decided to promote lightening of the agent. In the present invention, the oxygen contained in the assist exhaust can be used to promote the reaction between the reducing agent and oxygen in the reducing agent reforming catalyst. As a result, since the lightening and atomization of the reducing agent is promoted, the dispersibility of the reducing agent introduced into the exhaust passage can be further enhanced.

  Furthermore, in the present invention, the distribution region increasing means increases the distribution region of the reducing agent after or after the reducing agent passes through the reducing agent reforming catalyst. Examples of the distribution region increasing means in the present invention include a member that changes the traveling direction of the reducing agent and a member that weakens the penetration force of the reducing agent flowing into the exhaust passage. Thereby, a reducing agent can be disperse | distributed over the wider range in an exhaust passage. In addition, the area | region where the reducing agent distributes in this invention may mean the area | region where a reducing agent distributes in the cross section substantially orthogonal to the axis line of a fuel injection valve.

  By the way, in the present invention, the penetration force of the reducing agent flowing into the exhaust passage is weakened by passing the reducing agent reforming catalyst through the reducing agent before being introduced into the exhaust passage or by the distribution region increasing means. There is. In such a case, for example, the attachment of the reducing agent to the reducing agent reforming catalyst increases, and it may be difficult to efficiently introduce the reducing agent into the exhaust passage. In contrast, in the present invention, the assist exhaust is assisted to introduce the reducing agent into the exhaust passage. That is, according to the present invention, the reducing agent is vigorously introduced into the exhaust passage by utilizing the moment when the assist exhaust led to the spray region of the reducing agent by the particulate reducing agent introduction means flows into the exhaust passage. Can be made.

  As described above, in the present invention, by using a part of the exhaust gas that passes through the exhaust passage, the amount of assist exhaust that is necessary and sufficient for introducing the reducing agent into the exhaust passage suitably can be simply configured. Can be secured. Thereby, reduction of cost and downsizing of the reducing agent addition device can be realized.

Moreover, by adjusting the amount of assist exhaust, it is possible to easily secure as much oxygen as necessary to lighten the reducing agent in the reducing agent reforming catalyst. Further, since the assist exhaust gas is at a higher temperature than air, there is no risk that the reductant reforming catalyst will be deprived of heat excessively even if the reducing agent reforming catalyst is passed through a large amount of assist exhaust gas. That is, it can be suppressed that the reducing agent reforming catalyst loses its activity due to being cooled by the assist exhaust.

  Moreover, as a fine particle reducing agent introduction | transduction means in this invention, the following structures can be illustrated. That is, in the present invention, the particulate reducing agent introduction means includes a cylindrical member that covers the reducing agent injection valve so that a substantially cylindrical gap portion is formed on the side surface of the reducing agent injection valve, and the exhaust passage and the gap portion. And a communication path that communicates with each other. Further, a reduced diameter portion in which the inner diameter of the cylindrical member is reduced may be formed at least in the vicinity of the reducing agent spray region in the cylindrical member.

  According to the above configuration, a gap portion formed between the inner peripheral surface of the cylindrical member and the outer peripheral surface of the reducing agent injection valve via a communication passage, a part of the exhaust that passes through the exhaust passage as assist exhaust. Led to. Here, the assist exhaust proceeds toward the injection port of the reducing agent injection valve while rotating in the gap along the inner peripheral surface of the cylindrical member. The assist exhaust can be guided to the reducing agent spray region by rotating the assist exhaust along the reduced diameter portion of the cylindrical member having a reduced inner diameter.

  Here, since the gap portion in the present invention is formed in a substantially cylindrical shape, a vortex is formed in the assist exhaust gas that rotates in the gap portion. Thus, the collision between the assist exhaust and the reducing agent can be promoted by guiding the assist exhaust to the spray region of the reducing agent while forming the vortex. That is, atomization of the reducing agent can be further promoted.

  In the present invention, the particulate reducing agent introduction means connects the tubular member and the exhaust passage, and has a connection passage for introducing the reducing agent mixed with the exhaust gas introduced from the communication passage to the gap portion into the exhaust passage. Further, at least a part of the connection passage may be formed with an enlarged portion in which the flow passage area is enlarged, and the distribution region increasing means may include an enlarged portion in the connection passage.

  In this way, by passing the reducing agent through the enlarged portion of the connection passage, the region where the reducing agent is distributed can be increased before the reducing agent is introduced into the exhaust passage. The enlarged portion in the present invention may have an inner diameter that increases toward the exhaust passage in the vicinity of the connection portion of the connection passage with the exhaust passage.

  Further, in the present invention, a second enlarged portion in which the flow passage area is enlarged is formed in at least a part of the exhaust passage into which the reducing agent is introduced by the particulate reducing agent introduction means. You may comprise including the 2nd expansion part in a channel | path. Thereby, when the reducing agent introduced into the exhaust passage is allowed to pass through the second enlarged portion, the region where the reducing agent is distributed can be increased.

  As described above, according to the reducing agent addition apparatus according to the present invention, the reducing agent injected from the fuel injection valve can be suitably dispersed in the exhaust gas passing through the exhaust passage. As a result, when a reducing agent is added to the exhaust before flowing into the exhaust purification device (for example, NOx catalyst, particulate filter, etc.), the reducing agent can be supplied uniformly to the entire exhaust purification device, and the reducing agent in the exhaust purification device Can increase the reactivity.

Further, since the reducing agent injected from the fuel injection valve is lightened by the reducing agent reforming catalyst before being introduced into the exhaust passage, the reducing agent is disposed on the inner surface of the exhaust passage after being introduced into the exhaust passage. Becomes difficult to adhere. Thereby, it can suppress that the reducing agent injected from the reducing agent injection valve is wasted. Thereby, it can suppress that the supply amount of the reducing agent with respect to an exhaust gas purification device runs short.

  In the present invention, in the reducing agent addition device that is provided in the exhaust passage of the internal combustion engine and adds the reducing agent to the exhaust that passes through the exhaust passage, the reducing agent injected from the reducing agent injection valve is more exhausted in the exhaust. Can be dispersed

  The best mode for carrying out the present invention will be exemplarily described in detail below with reference to the drawings. It should be noted that the dimensions, materials, shapes, relative arrangements, and the like of the components described in this embodiment are intended to limit the technical scope of the invention only to those unless otherwise specified. is not.

  FIG. 1 is a diagram showing a schematic configuration of an internal combustion engine to which the reducing agent addition device 20 in the present embodiment is applied and its intake / exhaust system. An internal combustion engine 1 shown in FIG. 1 is a diesel engine having four cylinders 2. Each cylinder 2 is provided with a fuel injection valve 3 that directly injects fuel into the combustion chamber. Each fuel injection valve 3 is connected to a pressure accumulation chamber (common rail) 4, and the common rail 4 communicates with a fuel pump 6 through a fuel supply pipe 5.

  An exhaust manifold 8 is connected to the internal combustion engine 1, and each branch pipe of the exhaust manifold 8 communicates with the combustion chamber of each cylinder 2 through an exhaust port. Further, a turbine housing 10 a in which the turbine of the centrifugal supercharger 10 is stored is connected to the exhaust manifold 8 via a collecting pipe 9. An exhaust pipe 11 is connected to an opening through which the exhaust of the turbine housing 10a flows out. The exhaust pipe 11 is provided with an exhaust purification device 15 equipped with a NOx storage reduction catalyst (hereinafter referred to as “NOx catalyst”) for purifying NOx in the exhaust.

Further, in the exhaust pipe 11 downstream of the turbine 10 a and upstream of the exhaust purification device 15, fuel (for example, light oil) as a reducing agent is added to the exhaust before flowing into the exhaust purification device 15. A fuel addition device 20 to be added is provided. The fuel added from the fuel addition device 20 to the exhaust gas in the exhaust pipe 11 reduces the oxygen concentration of the exhaust gas. The exhaust gas thus formed with a low oxygen concentration flows into the NOx catalyst provided in the exhaust purification device 15 and is reduced to nitrogen (N ₂ ) while releasing NOx stored in the NOx catalyst. A NOx reduction process is performed.

  The exhaust pipe 11 is connected to a muffler (not shown) downstream of the exhaust purification device 15. Exhaust gas discharged from each cylinder 2 passes through an exhaust port, an exhaust manifold 8, a collecting pipe 9, and an exhaust pipe 11, and after the NOx in the exhaust gas is purified by the exhaust gas purification device 15, it enters the atmosphere through the muffler. Released. In the present embodiment, the exhaust port, the exhaust manifold 8, the collecting pipe 9, the exhaust pipe 11, etc., the passage through which the exhaust from the internal combustion engine 1 is released into the atmosphere constitutes the exhaust passage in the present invention.

The internal combustion engine 1 is provided with an ECU 19 that is an electronic control computer that controls the internal combustion engine 1. The ECU 19 includes a ROM, a RAM, a CPU, an input port, an output port, and the like (not shown). The ECU 19 controls the operation state of the internal combustion engine 1 and the operation state of the internal combustion engine 1 according to a request from the driver. It is a unit that performs such control.

FIG. 2 is a diagram showing a schematic configuration of the fuel addition device 20 in the present embodiment. A cylindrical needle 23 serving as a valve member is inserted into the cylindrical needle body 22 constituting the fuel addition valve 21 so as to be movable back and forth in the axial direction. An injection port 22 a through which fuel is injected is formed at the tip of the needle body 22, and the body 22 b of the needle body 22 and the fuel pump 6 are connected via a fuel introduction pipe 13.

  A valve capable of closing the injection port 22a of the needle body 22 is formed on one end side of the needle 23, and a coil spring (not shown) is connected to the other end side of the needle 23. As a result, the valve formed at the tip of the needle 23 is pressed against the injection port 22a by the biasing force of the coil spring and the fuel pressure supplied from the fuel pump 6 at normal times, and the injection port 22a is closed. Yes.

  Further, the fuel addition device 20 incorporates an electromagnetic actuator (not shown) constituted by a coil. This electromagnetic actuator is connected to the ECU 19 via electrical wiring, and energization of the coil and interruption of energization are performed based on a control signal from the ECU 19. That is, when the coil is energized by the command from the ECU 19 and the electromagnetic actuator is activated, the needle 23 is lifted against the urging force and fuel pressure to open the injection port 22a, and fuel is injected from the injection port 22a. . On the other hand, when the energization of the coil is interrupted and the operation of the electromagnetic actuator is released, the injection port 22a is closed again by the needle 23.

  The above-described needle body 22, needle 23, and the like constitute the fuel addition valve 21 in the present embodiment. Further, the fuel addition valve 21 of the present embodiment is arranged so that the axis is substantially orthogonal to the axis of the exhaust pipe 11. In this embodiment, the fuel addition valve 21 corresponds to the reducing agent injection valve in the present invention.

  Here, the outer peripheral portion of the needle body 22 is covered with a cylindrical outer housing 24 that is substantially coaxial with the needle body 22. The outer housing 24 is formed with a small-diameter portion 24a, a large-diameter portion 24b, and a taper portion 24c from the body 22b side of the needle body 22 toward the injection port 22a as shown in the figure. Here, the inner diameter of the small diameter portion 24a is equal to the outer diameter of the body portion 22b of the needle body 22, and the inner diameter of the large diameter portion 24b is larger than the outer diameter of the body portion 22b. The tapered portion 24c is formed in a portion covering the injection port 22a of the needle body 22 and the vicinity of the spray region of the fuel injected from the injection port 22a, and the inner surface thereof is formed in a tapered shape. More specifically, the inner diameter of the taper portion 24c is reduced from the body portion 22b side to the injection port 22a side in the axis of the fuel addition valve 21.

  The outer housing 24 formed as described above covers the outer periphery of the needle body 22, so that a cylindrical gap portion 25 as illustrated is provided between the outer peripheral surface of the needle body 22 and the inner peripheral surface of the outer housing 24. Is formed. In this embodiment, the outer housing 24 corresponds to the cylindrical member in the present invention, and the tapered portion 24c corresponds to the reduced diameter portion in the present invention.

  In the present embodiment, the tapered portion 24c of the outer housing 24 and the exhaust pipe 11 are connected via a connecting pipe 26 formed in a cylindrical shape. The inner diameter of the connection pipe 26 is constant at the connection portion side between the connection pipe 26 and the outer housing 24, and the connection pipe 26 and the exhaust pipe 11 are tapered toward the exhaust pipe 11 side. . Here, the portion where the inner diameter is kept constant is referred to as the same diameter portion 26a, and the portion formed in a tapered shape is referred to as the enlarged diameter portion 26b. In this embodiment, the connection pipe 26 corresponds to the connection passage in the present invention.

  Here, a catalyst 27 that promotes lightening of the fuel is interposed in the same-diameter portion 26 a of the connection pipe 26. The catalyst 27 is a straight flow type catalyst formed in a cylindrical shape. The base material constituting the catalyst 27 has a large number of cells partitioned by partition walls extending in the axial direction of the fuel addition valve 21, and an active metal having oxidizing ability is supported on the partition walls. In this embodiment, the catalyst 27 corresponds to the reducing agent reforming catalyst in the present invention.

  Further, a perforated plate 28 having a large number of through holes 28a (shown by broken lines in the figure) is provided in the enlarged diameter portion 26b in the vicinity of the connection portion between the enlarged diameter portion 26b and the exhaust pipe 11. . The perforated plate 28 is formed in the shape of a truncated cone, and the outer peripheral portion of the perforated plate 28 is disposed inscribed in the enlarged diameter portion 26b.

  Here, as shown in FIGS. 1 and 2, the collecting pipe 9 and the gap portion 25 b in this embodiment are communicated with each other via an exhaust introduction pipe 29. In the middle of the exhaust introduction pipe 29, a switching valve 29a capable of conducting or shutting off the collecting pipe 9 and the gap 25 is disposed. The switching valve 29a is connected to the ECU 19 via electrical wiring, and the switching valve 29a is switched based on a control signal from the ECU 19. In other words, the ECU 19 causes the collecting pipe 9 and the gap 25 to be electrically connected to the switching valve 29 a, so that a part of the exhaust gas passing through the collecting pipe 9 is guided to the gap 25 via the exhaust introduction pipe 29. In this embodiment, the exhaust introduction pipe 29 corresponds to the communication path in the present invention.

  Here, FIG. 3 is a cross-sectional view taken along the line XX in FIG. As shown in the figure, the exhaust introduction pipe 29 and the gap portion 25 are connected so that the exhaust that has passed through the exhaust introduction pipe 29 flows in a substantially tangential direction of the inner peripheral surface of the large diameter portion 24b of the outer housing 24. Yes.

As described above, the fuel addition device 20 in the present embodiment includes the fuel addition valve 21, the outer housing 24, the connection pipe 26, the exhaust introduction pipe 29, and the switching valve 29a. Hereinafter, fuel addition by the fuel addition device 20 in the present embodiment will be described by taking as an example a case where NOx reduction processing is performed on the NOx catalyst. When the NOx reduction process is performed, fuel addition control is performed in which the fuel addition device 20 adds fuel as a reducing agent into the exhaust gas. When this fuel is supplied to the NOx catalyst of the exhaust purification device 15, the NOx stored in the NOx catalyst is reduced. The control related to the NOx reduction process is performed based on a command signal from the ECU 19.

  In this embodiment, the ECU 19 estimates the NOx occlusion amount occluded in the NOx catalyst from the operating state history of the internal combustion engine 1, and the fuel addition control is executed when the NOx occlusion amount reaches a preset threshold value. The The threshold here is a value obtained by subtracting a predetermined margin from the amount of NOx that can be stored to the maximum by the NOx catalyst, and when the NOx storage amount exceeds this value, the NOx reduction process should be executed. It is a value that can be determined.

  The estimation of the NOx occlusion amount described above is executed by the ECU 19 every predetermined time when the internal combustion engine 1 is in operation. In this embodiment, when it is determined that the NOx storage amount is greater than or equal to the threshold value, the ECU 19 causes the collecting pipe 9 and the gap 25 to be electrically connected to the switching valve 29a. Since the exhaust before flowing into the turbine housing 10a flows in the collecting pipe 9, the pressure in the collecting pipe 9 is maintained relatively high. Therefore, when the collecting pipe 9 and the gap portion 25 are brought into conduction, a part of the exhaust gas passing through the collecting pipe 9 is guided to the gap portion 25 through the exhaust introduction pipe 29 (illustrated by an arrow A in FIG. 2).

  Here, as shown in FIG. 3, the exhaust led to the gap 25 via the introduction pipe 29 (hereinafter, this exhaust is referred to as “assist exhaust”) is the inner peripheral surface of the large-diameter portion 24 b of the outer housing 24. Therefore, the assist exhaust does not easily collide with the outer peripheral surface of the needle body 22, and the momentum when the assist exhaust flows from the exhaust introduction pipe 29 is suppressed. The assist exhaust rotates in the gap 25 along the inner circumferential surface of the large diameter portion 24b of the outer housing 24 in the direction of the arrow in the figure, and a vortex is formed in the assist exhaust.

Returning to FIG. 2, the assist exhaust in which the vortex is formed proceeds toward the injection port 22 a of the needle body 22 while rotating in the gap 25 (in FIG. 2, the arrow B and FIG. 3, (Shown with arrows). By the way, since the inner peripheral surface of the taper portion 24c is formed in a taper shape, the assist exhaust gas is formed when the assist exhaust gas is injected from the injection port 22a when rotating along the inner peripheral surface of the taper portion 24c. To the fuel spray area AHC (shown by arrow C in FIG. 2).

  In the fuel addition control in the present embodiment, the fuel is injected from the fuel addition valve 21 in accordance with the timing at which the assist exhaust reaches the fuel spray region AHC. As a result, the assist exhaust collides with the fuel injected by the fuel addition valve 21, so that the fuel particles can be made finer. That is, the atomization of the fuel can be promoted, so that the dispersibility of the fuel can be improved.

  Specifically, the fuel injection timing by the fuel addition valve 21 is experimentally obtained in advance by the time required for the assist exhaust to reach the fuel spray region AHC after the ECU 19 issues a command to the switching valve 30. You can keep it. In the present embodiment, the exhaust introduction pipe 29 and the gap 25 correspond to a path different from the exhaust passage in the present invention.

  As described above, the fuel whose assist exhaust and atomization are promoted flows into the catalyst 27 interposed in the connecting pipe 26 with the same diameter portion 26a. In the present embodiment, since the assist exhaust and the fuel are mixed and pass through the catalyst 27, the oxygen contained in the assist exhaust and the fuel can be efficiently reacted in the catalyst 27. Thereby, the lightening and atomization of the fuel can be promoted.

  Next, part of the assist exhaust and fuel that has flowed out of the catalyst 27 passes through the through hole 28a of the perforated plate 28 as it is and flows into the exhaust pipe 11, and the rest forms the through hole 28a of the perforated plate 28. It collides with a portion that has not been made (hereinafter referred to as “non-hole portion”). Thereby, the traveling direction of the assist exhaust and the fuel is changed, and the assist exhaust and the fuel are dispersed in the radial direction of the perforated plate 28 (illustrated by an arrow D in FIG. 2).

  Then, the fuel can easily pass through to the exhaust pipe 11 also from the through hole 28a formed at a position away from the axis of the fuel addition valve 21, so that the fuel is distributed in a cross section substantially orthogonal to the axis of the fuel addition valve 21. The area (hereinafter referred to as “distributed area in the orthogonal cross section”) can be increased (illustrated by an arrow E in FIG. 2). Thereby, the fuel can be dispersed over a wide range in the exhaust gas passing through the exhaust pipe 11.

  In addition, since the diameter-expanded part 26b of the connection pipe 26 in the present embodiment increases in a tapered shape toward the exhaust pipe 11, the distribution area in the orthogonal cross section can be increased more suitably. In the present embodiment, the perforated plate 28 and the enlarged diameter portion 26b in the connecting pipe 26 constitute the distribution region increasing means in the present invention. In the present embodiment, the enlarged diameter portion 26b of the connection pipe 26 corresponds to the enlarged portion of the connection passage in the present invention.

  As described above, according to the fuel addition control in the present embodiment, the fuel injected from the fuel addition valve 21 is once collided with the assist exhaust before being introduced into the exhaust pipe 11 and further passed through the catalyst 27. Fuel atomization and lightening can be promoted. Thereby, the dispersibility of the fuel when added to the exhaust gas passing through the exhaust pipe 11 can be enhanced. Moreover, the traveling direction of the fuel can be changed by the perforated plate 28 and the distribution area in the orthogonal cross section can be increased. As a result, the fuel injected by the fuel addition valve 21 can be more suitably dispersed into the exhaust gas that passes through the exhaust pipe 11.

Therefore, the fuel can be uniformly supplied to the entire NOx catalyst of the exhaust purification device 15, and the reactivity of the fuel in the NOx catalyst can be enhanced. As a result, the NOx reduction process can be efficiently performed, and the fuel consumption related to the NOx reduction process can be reduced.

  Further, since the atomization / lightening of the fuel injected from the fuel injection valve 21 is promoted, it becomes difficult for the fuel to adhere to the inner surface of the exhaust pipe 11, so that the fuel supplied to the NOx catalyst is reduced. Can be suppressed. That is, it is possible to reduce the waste of fuel related to the fuel addition control as much as possible and reduce the fuel consumption.

  Further, as in the present embodiment, passing the catalyst 27 and the perforated plate 28 through the fuel injected from the fuel addition valve 21 can be a resistance when the fuel is introduced into the exhaust pipe 11 at least. In this embodiment, the flow of fuel into the exhaust pipe 11 can be assisted by the momentum of the assist exhaust that sequentially passes through the exhaust introduction pipe 29.

  Further, since the temperature of the exhaust used as the assist exhaust is relatively high, even if the catalyst 27 is passed through a large amount of the assist exhaust, there is no possibility that the activity is lowered due to the catalyst 27 being excessively cooled. The particulate reducing agent introducing means in the present invention includes the fuel addition valve 21, the outer housing 24, the exhaust introduction pipe 29, the switching valve 29a, and the ECU 19 that performs control related to the fuel addition valve 21 and the switching valve 29a. It is comprised including.

  In the fuel addition device 20 of the present embodiment, the switching valve 29 a is not necessarily provided in the middle of the exhaust introduction pipe 29. In that case, when the internal combustion engine 1 is in operation, a part of the exhaust gas passing through the collecting pipe 9 is constantly introduced into the exhaust pipe 11 via the exhaust introduction pipe 29, but is released into the atmosphere. Since it passes through the exhaust purification device 15 before being performed, there is no possibility that the emission will deteriorate. Further, the arrangement of the fuel addition valve 21 with respect to the exhaust pipe 11 in the present embodiment has been described as an example in which the axis of the fuel addition valve 21 is orthogonal to the axis of the exhaust pipe 11, but within a range not departing from the spirit of the present invention Of course, it may be changed.

  Further, in the fuel addition control in the present embodiment, the fuel injected from the fuel addition valve 21 is added to the exhaust gas after flowing out of the turbine housing 10a and before flowing into the exhaust purification device 15, but the turbine housing Fuel may be added to the exhaust before flowing into 10a. Specifically, for example, fuel may be added to the exhaust manifold 8 or exhaust passing through the exhaust port.

  The fuel addition device 20 described above is an example for explaining the embodiment of the reducing agent addition device of the present invention, and various modifications can be made without departing from the gist of the present invention. Hereinafter, variations of the embodiment of the present invention will be described. 4 to 8 shown below, components common to the fuel addition device 20 shown in FIG. 2 are denoted by the same reference numerals, and illustration of some of the common components is omitted.

  FIG. 4 is a diagram showing a schematic configuration of the second fuel addition device 30 in the present embodiment. Here, the second fuel addition device 30 shown in FIG. 4 is different from the fuel addition device 20 shown in FIG. 2 in that a second perforated plate 31 is provided instead of the perforated plate 28. Similarly to the perforated plate 28, the second perforated plate 31 is formed in the shape of a truncated cone, and the outer peripheral portion of the second perforated plate 31 is disposed so as to be inscribed in the enlarged diameter portion 26b. The second perforated plate 31 also has a large number of through holes 31a (shown by broken lines in the figure). Here, the through hole 31a of the second perforated plate 31 is formed so as to spread radially from the inflow side end portion of the assist exhaust and the fuel toward the outflow side end portion.

In this way, by passing through the radially formed through holes 31a through the assist exhaust and fuel, the traveling direction of the assist exhaust and fuel at the time of inflow and outflow to the through hole 31a is changed (in FIG. 4, arrows And the distribution area in the orthogonal cross section can be further expanded. In the second fuel addition device 30, the shapes and the like of the second connection pipe 32, the second perforated plate 31, and the through hole 31a may be appropriately changed within the scope of the technical idea of the present invention. The total cross-sectional area of the through holes 31a formed in the second perforated plate 31, the density, the cross-sectional shape of the through holes 31a, and the like can be changed as appropriate.

  Next, the 3rd fuel addition apparatus 40 in a present Example is demonstrated. FIG. 5 is a diagram showing a schematic configuration of the third fuel addition device 40 in the present embodiment. The third fuel addition device 40 is different from the fuel addition device 20 shown in FIG. 2 in that the tapered portion 24 c of the outer housing 24 and the exhaust pipe 11 are connected via the second connection pipe 32. The second connection pipe 32 has substantially the same shape as the diameter-expanded portion 26b of the connection pipe 26 constituting the fuel addition device 20, and has a diameter increased in a tapered shape toward the exhaust pipe 11 side. In the third fuel addition device 40, the second connection pipe 32 corresponds to the connection passage in the present invention, and constitutes an enlarged portion of the connection passage in the present invention.

  The second connection pipe 32 is provided with a straight flow type second catalyst 33 formed in the shape of a truncated cone. The base material constituting the second catalyst 33 has a large number of cells 33b partitioned by the partition walls 33a, and the partition walls 33a carry an active metal having an oxidizing ability. Further, the partition wall 33a is inclined with respect to the axis of the fuel addition valve 21 so that the cross-sectional area of the cell 33b (the flow area of the fuel and the assist exhaust) increases toward the downstream side in the passage direction of the fuel and the assist exhaust. .

  When the fuel and the assist exhaust gas are flown into the second catalyst 33 configured as described above, the fuel and the assist exhaust gas can flow through the second catalyst 33 while spreading in the radial direction of the second catalyst 33 (FIG. 5). Middle, illustrated by arrows). As a result, the distribution area in the orthogonal cross section can be increased when the fuel and assist exhaust flow out of the second catalyst 33 compared to when the fuel and assist exhaust flow into the second catalyst 33. In this case, the second catalyst 33 corresponds to the reducing agent reforming catalyst in the present invention. Further, the second catalyst 33 and the second connecting pipe 32 constitute the distribution region increasing means in the present invention.

  Moreover, FIG. 6 is a figure which shows schematic structure of the 4th fuel addition apparatus 50 in a present Example. The fourth fuel addition device 50 is arranged so that the axis of the fuel addition valve 21 is substantially parallel to the axis of the exhaust pipe 11, and the tapered portion 24 c of the outer housing 24 and the exhaust pipe 11 are disposed via the third connection pipe 34. 2 is different from the fuel addition device 20 shown in FIG.

  The third connection pipe 34 is formed in a cylindrical shape, like the connection pipe 26 constituting the fuel addition device 20. The third connecting pipe 34 in the fourth fuel addition device 50 is formed to be bent halfway. That is, the axial direction of the third connecting pipe 34 is substantially parallel to the axial direction of the fuel addition valve 21 on the side of the connecting portion with the outer housing 24, but gradually changes from the middle. The axial direction of the third connection pipe 34 is substantially orthogonal to the axial direction of the fuel addition valve 21 and the exhaust pipe 11 on the connection portion side with the exhaust pipe 11. The inner diameter of the bent portion of the third connecting pipe 34 is increased in a tapered shape, and the inner diameter of the exhaust pipe 11 side is larger than that of the bent portion than the outer housing 24 side (hereinafter referred to as the first portion). The bent portion of the three connecting pipe 34 is referred to as “bent enlarged diameter portion 34a”). Further, an exhaust pipe side enlarged diameter portion 34b whose inner diameter is tapered toward the exhaust pipe 11 side is formed in the vicinity of the connection portion of the third connection pipe 34 with the exhaust pipe 11.

  According to the fourth fuel addition device 50 configured as described above, the fuel added from the fuel addition valve 21 and whose atomization and lightening are promoted flows into the third connection pipe 34 together with the assist exhaust. Since the flow path area of the third connecting pipe 34 increases at the bent enlarged diameter portion 34a, the fuel mixed with the assist exhaust is easily dispersed in the assist exhaust when passing through the third connecting pipe 34a.

  In addition, since the flow passage area is further increased in the exhaust pipe side enlarged diameter portion 34b, the fuel in the assist exhaust can be further dispersed. Further, since the perforated plate 28 is disposed in the exhaust pipe side enlarged diameter portion 34b, the perforated plate 28 is passed through the fuel and the assist exhaust to increase the distribution area in the orthogonal cross section. Can be introduced into the exhaust pipe 11. Thereby, the fuel added by the fuel addition valve 21 can be suitably dispersed into the exhaust gas passing through the exhaust pipe 11.

  In the fourth fuel addition device 50, the third connection pipe 34 corresponds to the connection passage in the present invention. Further, the bent enlarged diameter portion 34a and the exhaust pipe side enlarged diameter portion 34b correspond to the enlarged portion of the connection passage in the present invention. Further, in the above configuration, the distribution region increasing means in the present invention is configured including the bent enlarged portion 34a, the exhaust pipe side enlarged portion 34b, and the perforated plate 28. The arrangement of the fuel addition valve 21 and the exhaust pipe 11 in FIG. 6 is merely an example, and it goes without saying that the axis of the fuel addition valve 21 may not be substantially parallel to the axis of the exhaust pipe 11.

  FIG. 7 is a diagram showing a schematic configuration of the fifth fuel addition device 60 in the present embodiment. The fifth fuel addition device 60 is different from the fuel addition device 20 shown in FIG. 2 in that the tapered portion 24 c of the outer housing 24 and the exhaust pipe 11 are connected via a fourth connection pipe 35. The fourth connecting pipe 35 has substantially the same shape as the same diameter portion 26a of the connecting pipe 26 constituting the fuel addition device 20, and has a constant inner diameter. A catalyst 27 is disposed inside the fourth connecting pipe 35. Yes. Further, the fifth fuel addition device 60 is different from the fuel addition device 20 shown in FIG. 2 in that the perforated plate 28 is not provided.

  Here, when the flow direction of the exhaust gas in the exhaust pipe 11 is indicated by an arrow in the drawing, the inner diameter of the exhaust pipe 11 is increased in a taper shape immediately downstream of the connection part of the exhaust pipe 11 and the fourth connection pipe 35. An exhaust pipe enlarged diameter portion 11a is formed. According to this, the fuel in the exhaust can be further dispersed when the fuel introduced into the exhaust pipe 11 passes through the exhaust pipe enlarged diameter portion 11a. In the fifth fuel addition device 60, the fourth connection pipe 35 corresponds to the connection passage in the present invention. Further, the exhaust pipe enlarged diameter portion 11a corresponds to the second enlarged portion of the exhaust passage in the present invention, and constitutes the distribution region increasing means in the present invention.

  FIG. 8 is a view showing a modified example of the exhaust pipe enlarged diameter portion 11a shown in FIG. As shown in the figure, the exhaust pipe 11 is formed so as to be bent at a portion immediately downstream of the connection portion with the fourth connection pipe 35. In the bent portion of the exhaust pipe 11, the inner diameter is increased in a tapered shape. That is, the portion of the exhaust pipe 11 downstream of the bent portion has a larger inner diameter than the portion of the upstream side of the bent portion (hereinafter, the bent portion of the exhaust pipe 11 is referred to as “exhaust pipe bent expansion”). Referred to as a diameter portion 11b). According to the above configuration, when the fuel introduced into the exhaust pipe 11 is allowed to pass through the exhaust pipe bent enlarged diameter portion 11b, the fuel is easily dispersed in the exhaust. In the above configuration, the exhaust pipe bending enlarged portion 11b corresponds to the second enlarged portion of the exhaust passage in the present invention, and constitutes the distribution region increasing means in the present invention. Of course, the exhaust pipe 11 in the present embodiment may be formed with both the exhaust pipe enlarged diameter portion 11a and the exhaust pipe bent enlarged diameter portion 11b.

  As described above, according to the fuel addition device 20 to the fifth fuel addition device 60 exemplified in this embodiment, the fuel from the fuel addition valve 21 can be suitably dispersed in the exhaust gas. Further, the constituent elements of the fuel addition device 20 to the fifth fuel addition device 60 described in the present embodiment can be combined as much as possible without departing from the spirit of the present invention.

In the present embodiment, the tapered portion 24c of the outer housing 24 and the exhaust pipe 11 are connected via the connection pipe 26 to the fourth connection pipe 35 as the connection passage in the present invention, and the fuel and the assist exhaust are exhausted from the exhaust pipe. 11 is not intended to be limited to this. For example, the connection pipe 26 to the fourth connection pipe 35 may be configured by a part of the exhaust pipe 11. Alternatively, the tapered portion 24c of the outer housing 24 and the exhaust pipe 11 may be directly connected. For example, an opening for introducing fuel and assist exhaust into the exhaust pipe 11 may be formed, and the taper 24c and the exhaust pipe 11 may be connected so that the tip of the taper 24c faces the opening.

In the present embodiment, the case where the NOx storage reduction catalyst is disposed in the exhaust purification device 15 has been described as an example, but the present invention is not limited to this. For example, the present invention may be applied to an exhaust gas purification system including an exhaust gas purification device 15 in which a particulate filter carrying an oxidation catalyst is arranged or an oxidation catalyst and a particulate filter are arranged in series from the upstream side. That is, the PM regeneration process is executed to raise the temperature of the particulate filter by reaction heat when the fuel as the reducing agent is oxidized by executing the fuel addition control, and to oxidize and remove the particulates collected by the particulate filter. Also good.

  Further, when the exhaust gas purification device 15 in the present embodiment is provided with a selective reduction type NOx catalyst, urea water as a reducing agent is supplied to the selective reduction type NOx catalyst when performing the NOx reduction process. In that case, a hydrolysis catalyst may be employed as the catalyst 27 or the second catalyst 33 in this embodiment. As a result, urea water reacts in the catalyst to generate an ammonia component. By supplying this ammonia component to the selective reduction type NOx catalyst, NOx can be efficiently purified.

It is a figure which shows schematic structure of the internal combustion engine to which the reducing agent addition apparatus in Example 1 is applied, and its intake / exhaust system. It is a figure which shows schematic structure of the fuel addition apparatus in Example 1. FIG. It is sectional drawing of the XX cross section in FIG. It is a figure which shows schematic structure of the 2nd fuel addition apparatus in Example 1. FIG. It is a figure which shows schematic structure of the 3rd fuel addition apparatus in Example 1. FIG. It is a figure which shows schematic structure of the 4th fuel addition apparatus in Example 1. FIG. It is a figure which shows schematic structure of the 5th fuel addition apparatus in Example 1. FIG. It is a figure which shows the modification of the exhaust pipe enlarged diameter part shown in FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Internal combustion engine 3 ... Fuel injection valve 9 ... Collecting pipe 10 ... Centrifugal supercharger 11 ... Exhaust pipe 15 ... Exhaust gas purification device 19 ... ECU
20, Fuel addition device 21, Fuel addition valve 22, Needle body 22a, Injection port 24, Outer housing 24c, Tapered portion 25, Gap portion 26, Connection pipe 27, Catalyst 28, Perforated plate 29 ・ ・ Exhaust pipe 29a ・ Switching valve

Claims (4)

A reducing agent addition device for adding a reducing agent to exhaust gas passing through an exhaust passage of an internal combustion engine,
A reducing agent injection valve for injecting the reducing agent;
A part of the exhaust gas passing through the exhaust passage is led to a spray region of the reducing agent injected by the reducing agent injection valve via a path different from the exhaust passage to promote atomization of the reducing agent, and the different Fine particulate reducing agent introduction means for introducing exhaust and reducing agent through the passage into the exhaust passage;
A reducing agent reforming catalyst that promotes lightening of the reducing agent before the reducing agent after mixing with the exhaust via the different paths is introduced into the exhaust passage;
A distribution region increasing means for increasing a region where the reducing agent is distributed after the reducing agent passes through the reducing agent reforming catalyst or when passing through the reducing agent reforming catalyst;
A reducing agent addition device for an internal combustion engine, comprising: The particulate reducing agent introduction means includes a cylindrical member that covers the reducing agent injection valve so that a substantially cylindrical gap is formed on a side surface of the reducing agent injection valve, and the exhaust passage and the gap. And a communication path that communicates,
The reduced diameter part in which the internal diameter of this cylindrical member is reducing is formed in the part located in the spray area | region of the said reducing agent at least in the said cylindrical member. A reducing agent addition device for an internal combustion engine. The particulate reducing agent introduction means further includes a connection passage for connecting the tubular member and the exhaust passage, and for introducing the reducing agent mixed with the exhaust led to the gap from the communication passage into the exhaust passage. And
At least a part of the connection passage is formed with an enlarged portion in which the flow area is enlarged,
3. The reducing agent addition device for an internal combustion engine according to claim 2, wherein the distribution region increasing means includes the enlarged portion in the connection passage. At least a part of the exhaust passage into which the reducing agent is introduced by the particulate reducing agent introduction means is formed with a second enlarged portion in which the flow passage area is enlarged,
The reducing agent addition device for an internal combustion engine according to claim 2 or 3, wherein the distribution region increasing means includes the second enlarged portion in the exhaust passage.

Images