JP5561486B2 - Exhaust purification device - Google Patents

Description

  The present invention relates to an exhaust emission control device.

  In exhaust gas exhausted from engines mounted on automobiles, especially diesel engines, carbon monoxide (CO), hydrocarbons (HC), nitrogen oxides (NOx), and particulate matter (PM) ) Etc. are included. For this reason, in general, an exhaust gas purification catalyst such as a three-way catalyst or the like for capturing PM in an exhaust passage through which exhaust gas discharged from an engine passes, for example, to decompose (reducing, etc.) the above substances The particulate filter or the like is provided so that the exhaust gas is discharged into the atmosphere as harmless as possible.

  In the particulate filter, PM accumulates in the filter with use and the passage resistance increases. Therefore, it is necessary to perform a regeneration process as necessary. As such a regeneration process, a hydrocarbon-based liquid such as fuel (light oil) is caused to flow into an oxidation catalyst provided upstream of the particulate filter to cause an exothermic reaction, and this heat causes the particulate filter to be regenerated. A method of performing this has been proposed (for example, see Patent Document 1). In Patent Document 1, an injector is installed at an end of a housing portion that communicates with an exhaust passage, and an additive is injected from the injector to an oxidation catalyst provided in the exhaust catalyst. Here, the accommodating portion is provided with an opening / closing means that can be opened and closed with respect to the exhaust passage, and is configured to drive the opening / closing means based on the temperature of the exhaust gas.

JP 2010-116908 A (FIG. 1, claims 1 to 3 etc.)

  However, according to the above configuration, exhaust gas does not sufficiently flow into the injection space of the injector, so that the injection space becomes sooted with fuel and the fuel easily stays in the injection space. The remaining fuel becomes a binder, soot adheres in the injection space by this binder, and deposits are generated, thereby blocking the injection hole and the injection space of the injector. If the injection hole or injection space is blocked by the deposit in this way, the supply of the additive becomes insufficient, a response delay of the air-fuel ratio control occurs, a regeneration process of DPF (Diesel Particulate Filter), NOx There is a problem that the decomposition (reduction) treatment cannot be performed sufficiently.

  The present invention has been made in view of such circumstances, so that the soot and fuel accumulated in the injection hole and the injection space of the injector are removed before the deposit is generated, thereby generating the deposit. An object of the present invention is to provide an exhaust emission control device that suppresses the injection hole and the injection space from being blocked.

  The exhaust purification device of the present invention includes an exhaust passage connected to an exhaust port of an engine, an exhaust purification catalyst provided in the exhaust passage, and an exhaust passage upstream of the exhaust purification catalyst in the exhaust passage. An additive injection path that communicates with the injector, and an injector that injects the additive into the additive injection path and supplies the additive to the exhaust gas purification catalyst; the exhaust path facing the injector and the additive A partition member provided apart from the injection path and having a passage through which the additive injected from the injector passes, and provided in a gap between the partition member and the additive injection path, and from the exhaust path A shutter member that isolates the additive injection path, the shutter member is openable and closable, and is opened when the additive is not injected from the injector, and the additive injection path And performing the scavenging with the serial exhaust path.

  In the present invention, there is provided a shutter member provided in the gap between the partition wall member and the additive injection path, and isolating the additive injection path from the exhaust path, and the shutter member is openable and closable, and the injector The PM and fuel remaining in the additive injection path can be scavenged by entering the open state when no additive is injected from the exhaust gas and scavenging between the additive injection path and the exhaust path. In this way, it is possible to prevent the remaining fuel from becoming a binder and soot in the injection space and sticking to form a deposit. And since the shutter member will be in a closed state when the additive is injected from the injector, it can suppress that exhaust gas flows in into an additive injection path.

  The additive injection path is provided with a secondary air introduction path for introducing secondary air into the additive injection path, and when the shutter member is in an open state, the additive injection path from the secondary air introduction path It is preferable to be introduced into the road. By introducing the secondary air, it is easier to scavenge PM and fuel remaining in the additive injection path.

  It is preferable that a guide member for guiding the secondary air introduced from the secondary air introduction path to the injector side and supplying the air is provided in the exhaust path. Since the secondary air can be guided and supplied to the injector side by such a guide member, it is easier to scavenge PM and fuel remaining in the additive injection path.

  Further, it is preferable that the shutter member and the secondary air introduction path are provided at positions facing each other across the guide member. By being provided in this way, secondary air can be guided to the injector side, and when the shutter member is in an open state, air can be supplied to the outside from this shutter member. It is easier to scavenge the entire agent injection path.

  A cylindrical member extends from the partition member toward the injector, a hollow portion of the cylindrical member communicates with the passage port, and an opening area of the passage port of the hollow portion is on the injector side. It is preferable to be configured so as to become smaller. By providing the cylindrical member, the additive injected from the injector can go straight toward the exhaust purification catalyst without being affected by the flow of exhaust gas, and spray the additive more evenly on the exhaust purification catalyst. It is possible.

  According to the exhaust emission control device of the present invention, PM and fuel remaining in the additive injection path can be scavenged, so that the generation of deposits can be suppressed and the injection hole and injection space of the injector can be blocked. It is possible to prevent this.

It is a schematic diagram which shows schematic structure of an exhaust gas purification apparatus. It is sectional drawing which shows the principal part of an exhaust gas purification apparatus. It is sectional drawing which shows the principal part of an exhaust gas purification apparatus. It is sectional drawing which shows the principal part of an exhaust gas purification apparatus. It is sectional drawing which shows the principal part of an exhaust gas purification apparatus.

  FIG. 1 is a schematic diagram illustrating a configuration of an exhaust emission control device according to the present embodiment. As shown in FIG. 1, the exhaust purification device 10 has a plurality of exhaust purification catalysts and exhaust purification filters, and the plurality of exhaust purification catalysts and exhaust purification filters are installed in a vehicle. An exhaust pipe (exhaust passage) 12 of a cylinder diesel engine (hereinafter simply referred to as an engine) 11 is provided.

  The engine 11 includes a cylinder head 13 and a cylinder block 14, and a piston 16 is accommodated in each cylinder bore 15 of the cylinder block 14 so as to be reciprocally movable. A combustion chamber 17 is formed by the piston 16, the cylinder bore 15, and the cylinder head 13. The piston 16 is connected to a crankshaft 19 via a connecting rod 18 so that the crankshaft 19 is rotated by the reciprocating motion of the piston 16.

  An intake port 20 is formed in the cylinder head 13, and an intake pipe (intake passage) 22 including an intake manifold 21 is connected to the intake port 20. The intake port 20 is provided with an intake valve 23, and the intake port 20 is opened and closed by the intake valve 23. An exhaust port 24 is formed in the cylinder head 13, and an exhaust pipe (exhaust passage) 12 including an exhaust manifold 25 is connected to the exhaust port 24. The exhaust port 24 is provided with an exhaust valve 26. Like the intake port 20, the exhaust port 24 is opened and closed by the exhaust valve 26. A turbocharger 27 is provided in the middle of the intake pipe 22 and the exhaust pipe 12, and an exhaust purification catalyst and an exhaust purification catalyst that constitute the exhaust purification apparatus 10 are disposed downstream of the turbocharger 27 of the exhaust pipe 12. A filter is installed.

  The turbocharger 27 has a turbine (not shown) and a compressor connected to the turbine. When exhaust gas flows from the engine 11 into the turbocharger 27, the turbine is rotated by the flow of the exhaust gas, and the rotation of the turbine. Accordingly, the compressor is rotated so that air is sucked into the turbocharger 27 from the intake pipe 28 which is a part of the intake pipe 22 and pressurized. The air pressurized by the turbocharger 27 is supplied to each intake port 20 of the engine 11 through an intake pipe 29 that is a part of the intake pipe 22.

  The cylinder head 13 is provided with an electronically controlled fuel injection valve 30 that directly injects fuel into the combustion chamber 17 of each cylinder. The fuel injection valve 30 has a predetermined fuel pressure from a common rail (not shown). Controlled high pressure fuel is supplied.

  In this embodiment, a diesel oxidation catalyst (hereinafter simply referred to as an oxidation catalyst) 31 and a NOx trap catalyst 32 that are exhaust purification catalysts, and a diesel that is an exhaust purification filter are connected to the exhaust pipe 12 downstream of the turbocharger 27. A particulate filter (DPF: Diesel Particulate Filter: hereinafter referred to as DPF) 33 is arranged in order from the upstream side. An injector 35 that injects fuel (light oil), which is an additive (reducing agent), into the exhaust passage 34 is disposed in the exhaust passage 34 that forms part of the exhaust pipe 12 between the turbocharger 27 and the oxidation catalyst 31. Is provided via the additive injection path 36.

The oxidation catalyst 31 is formed by, for example, supporting a noble metal such as platinum (Pt) or palladium (Pd) on a honeycomb structure carrier made of a ceramic material. In the oxidation catalyst 31, when exhaust gas flows in, nitrogen monoxide (NO) in the exhaust gas is oxidized to generate nitrogen dioxide (NO ₂ ). Further, in order for the oxidation reaction in the oxidation catalyst 31 to occur, the oxidation catalyst 31 needs to be heated to a predetermined temperature or higher, and therefore the oxidation catalyst 31 may be arranged as close to the engine 11 as possible. preferable. This is because the oxidation catalyst 31 is heated by the heat of the engine 11 and the oxidation catalyst 31 can be heated to a predetermined temperature or higher in a relatively short time even when the engine is started.

In the NOx trap catalyst 32, for example, a noble metal such as platinum (Pt) or palladium (Pd) is supported on a honeycomb structure carrier made of aluminum oxide (AL ₂ O ₃ ), and barium (Ba) or the like is used as a storage agent. An alkali metal or alkaline earth metal is supported. The NOx trap catalyst 32 temporarily stores NOx in the oxidizing atmosphere, that is, NO ₂ generated by the oxidation catalyst 31 and NO remaining in the exhaust gas without being oxidized by the oxidation catalyst 31. In a reducing atmosphere containing carbon (CO), hydrocarbon (HC), etc., NOx is released and reduced to nitrogen (N ₂ ) or the like.

Further, most of the NO ₂ produced by the oxidation catalyst 31 is adsorbed / decomposed (reduced) by the NOx trap catalyst 32, and the remaining NO _{2 that} has not been adsorbed / decomposed is purified by the reaction in the DPF 33. .

  Normally, most of the exhaust gas discharged from the engine 11 is occupied by NO and the amount of HC is very small. Therefore, the inside of the NOx trap catalyst 32 becomes an oxidizing atmosphere, and the NOx trap catalyst 32 only adsorbs NOx. NOx that has been released is not decomposed (reduced). For this reason, when a predetermined amount of NOx is adsorbed to the NOx trap catalyst 32, fuel (light oil) as an additive is injected from the injector 35 fixed to the exhaust passage 34 between the turbocharger 27 and the oxidation catalyst 31. It has become so. As a result, the exhaust gas mixed with fuel passes through the oxidation catalyst 31 and is supplied to the NOx trap catalyst 32. The inside of the NOx trap catalyst 32 becomes a reducing atmosphere, and the adsorbed NOx is decomposed (reduced). The NOx trap catalyst 32 stores and decomposes (reduces) sulfur oxide (SOx) as well as nitrogen oxide (NOx).

  For example, the DPF 33 is a filter having a honeycomb structure formed of a ceramic material. The DPF 33 includes, for example, an exhaust gas passage 37 having an upstream end opened and a downstream end closed, and a downstream end. Exhaust gas passages 38 opened and closed at the upstream end are alternately arranged. The exhaust gas first flows into the exhaust gas passage 37 whose upstream end is opened, and the exhaust whose downstream end is opened from the porous wall surface provided between the adjacent exhaust gas passages 37. The gas flows into the gas passage 38 and flows downstream, and in this process, particulate matter (PM) in the exhaust gas collides with the wall surface or is adsorbed and captured.

The trapped PM is oxidized (combusted) by NO ₂ in the exhaust gas and discharged as CO ₂ . Alternatively, the exhaust gas temperature is forcibly raised by supplying fuel to the oxidation catalyst 31, and the PM deposited on the DPF is oxidized. In this way, the PM accumulated in the DPF is burned, so that the performance of the DPF 33 is regenerated to some extent.

Normally, as described above, since NOx is adsorbed by the NOx trap catalyst 32, the amount of NO _{2 in} the exhaust gas supplied to the DPF 33 is small, and PM is gradually deposited on the DPF 33. When a predetermined amount of PM accumulates in the DPF 33, a predetermined amount of fuel is injected from the injector 35 fixed to the exhaust passage 34. As described above, when the fuel is mixed with the exhaust gas, the NOx trapped by the NOx trap catalyst 32 is reduced, so that NOx (NO ₂ ) contained in the exhaust gas is not adsorbed by the NOx trap catalyst 32. To the DPF 33. As a result, PM combustion in the DPF 33 is promoted.

  An exhaust temperature sensor 39 is provided in the vicinity of the upstream side of the oxidation catalyst 31, the NOx trap catalyst 32 and the DPF 33, and in the vicinity of the downstream side of the DPF 33, and the oxidation catalyst 31, The temperature of the exhaust gas flowing into the NOx trap catalyst 32 and the DPF 33 and the temperature of the exhaust gas discharged from the oxidation catalyst 31, the NOx trap catalyst 32 and the DPF 33 are detected. Further, an oxygen concentration sensor 40 for detecting the oxygen concentration in the exhaust gas is provided in the vicinity of the upstream side of the oxidation catalyst 31 and the DPF 33. The vehicle is provided with an electronic control unit (ECU) (not shown). The ECU includes an input / output device, a storage device for storing a control program and a control map, a central processing unit, a timer and a counter. There is a kind. The ECU performs comprehensive control of the engine 11 and the exhaust purification device 10 based on information from the sensors.

  FIG. 2 is an enlarged cross-sectional view showing a main part of the exhaust gas purification apparatus according to the present embodiment. An exhaust passage 34 which is a part of the exhaust pipe 12 is configured by a hollow upstream member 41 connected to a turbocharger 27 (not shown in FIG. 2) and a catalyst holding member 42 connected to the upstream member 41. Yes. An oxidation catalyst 31 is provided on the catalyst holding member 42 via a fixing member 43.

  The upstream member 41 will be described in detail. The upstream member 41 has an inflow port 44 that is one end on the turbocharger side opened upward in FIG. 2, and an outflow port 45 at the other end on the oxidation catalyst 31 side opened downward in FIG.

  The inlet 44 into which the exhaust gas flows is configured to have a smaller inner diameter than the outlet 45 from which the exhaust gas flows out. The outlet 45 is formed to have the same diameter as the catalyst holding member 42. That is, the upstream member 41 includes an inflow port 44 into which exhaust gas flows, an inflow portion having an inner diameter substantially the same as the inflow port 44, and a wide portion 46 connected to the inflow portion and having an inner diameter wider than the inflow port 44. Thus, the outlet 45 that is the end of the wide portion 46 opposite to the inlet 44 is configured to have the same diameter as the catalyst holding member 42.

  Further, the upstream member 41 is provided with an additive injection path 36 communicating with (opening) the wide portion 46. That is, the additive injection path 36 communicates with the exhaust path 34. In the present embodiment, the additive injection path 36 is provided with a base end portion on the left wall surface in FIG. 2 of the wide portion 46, and in the substantially same direction (upward direction in FIG. 2) as the extending direction of the inflow portion. The tip is extended.

  An injector 35 is provided at the tip of the additive injection path 36. Thus, by providing the injector 35 via the additive injection path 36, it is possible to prevent the injector 35 from coming into direct contact with the main stream of high-temperature exhaust gas.

  The injector 35 is held by a holding member 47 at the tip of the additive injection path 36. The holding member 47 has a flange portion 48, and the flange portion 48 is fixed to the additive injection path 36 by a fixing member (not shown). The injector 35 is held by the holding member 47 in a state where the tip (injection hole) of the injector 35 is not exposed in the additive injection path 36. A cooling water passage 49 surrounding the injector 35 is formed inside the holding member 47. The injector 35 is cooled by the cooling water passage 49 and is provided so as not to be directly exposed in the additive injection passage 36 by the holding member 47, so that the injector 35 is always kept from overheating.

  The main flow of the exhaust gas flowing in from the inflow port 44 and the fuel injected from the injector 35 and passing through the additive injection path 36 are mixed in the wide portion 46 of the upstream member 41 and then contact the oxidation catalyst 31. In this embodiment, as will be described later, the fuel can come into contact with the entire upstream end surface of the oxidation catalyst 31.

  Here, in the present embodiment, a partition wall portion 51 is provided in the vicinity of the proximal end portion of the additive injection path 36 of the upstream member 41 so as to face the injector 35. One end of the partition wall 51 is fixed to the left inner wall surface of the upstream member 41 in FIG. 2, and the other end protrudes into the exhaust passage 34, that is, protrudes into the exhaust passage 34. That is, the partition wall portion 51 is provided to face the injector 35 and be separated from the additive injection path 36. Although not shown, the partition wall 51 is fixed to the inner wall surface of the upstream member 41 on the front and rear inner wall surfaces in FIG.

  In addition, a passage port 52 is formed in the partition wall portion 51 so as to face the injector 35. The passage port 52 has a substantially circular shape, and the fuel injected from the injector 35 passes through the passage port 52 and comes into contact with the oxidation catalyst 31.

  A cylindrical member 53 is provided on the surface of the partition wall 51 on the injector 35 side so as to extend from the partition wall 51. The cylindrical member 53 is cylindrical and has a hollow portion formed therein. The hollow portion of the tubular member 53 communicates with the passage port 52, and the hollow portion has the same inner diameter as the passage port 52 on the partition wall 51 side, and the inner diameter is smaller than that of the passage port 52 on the injector 35 side. It is configured as follows.

  Further, in the gap between the partition wall portion 51 and the additive injection path 36, specifically, the inner wall surface of the other end side where the partition wall portion 51 is not fixed and the upstream member 41 facing the other end side. A shutter member 54 is provided in the gap. The additive injection path 36 is isolated from the exhaust path 34 by the shutter member 54 and the partition wall 51.

  The shutter member 54 can be freely opened and closed, and its opening and closing is controlled by a control device (not shown). By opening the shutter member 54, scavenging is performed between the additive injection path 36 and the exhaust path 34.

  Further, a secondary air inlet 55 is provided near the base end opening of the additive injection path 36 of the upstream member 41 at a position facing the wall surface of the cylindrical member 53. The secondary air inlet 55 and the shutter member 54 are provided at positions facing each other with the cylindrical member 53 interposed therebetween. The secondary air introduction port 55 is configured to be able to introduce secondary air sucked by the engine into the additive injection path 36.

  In this embodiment, as shown in FIG. 3, when the fuel F is injected from the injector 35, the injected fuel F is guided by the cylindrical member 53 and reaches the entire front surface of the oxidation catalyst 31 via the passage port 52. can do.

  As shown in FIG. 4, when the partition member 51, the cylindrical member 53, and the shutter member 54 are not provided in the upstream member 41, a part of the exhaust gas in the exhaust passage 34 flows into the additive injection passage 36. As a result, the flow of the fuel F is obstructed and the fuel is caused to flow, and cannot reach all of the upstream end face of the oxidation catalyst 31.

  On the other hand, in the present embodiment, the cylindrical member 53 is provided, so that the fuel F can reach a desired arrival position without being obstructed by the flow of exhaust gas in the exhaust passage 34, and the oxidation catalyst 31. The entire front can be reached.

  Further, since the shutter member 54 is closed when the fuel F is injected from the injector 35, the inflow of the exhaust gas to the injector 35 side in the additive injection path 36 can be prevented. As a result, the introduction of soot into the additive injection path 36, which is a cause of deposit generation, is suppressed, and generation of deposits can be suppressed.

  When the fuel injection from the injector 35 is completed, the shutter member 54 is opened as shown in FIG. 5 by a control device (not shown). Thereby, the secondary air S is introduced into the additive injection path 36. The introduced secondary air S is guided by the outer wall surface of the cylindrical member 53 and flows into the injector 35, and then flows out from the opened shutter member 54 to the exhaust path 34. Thereby, the fuel which remained in the additive injection path 36 can be removed, and the production | generation of such a deposit can be suppressed. That is, if there is no air flow inside and outside of the additive injection path 36, the fuel remaining in the additive injection path 36 in a stagnant state becomes a binder. The soot adheres and deposits are generated, and the injection hole and injection space of the injector are blocked.

  On the other hand, in the present embodiment, since the shutter member 54 is in the open state, the secondary air can be introduced from the secondary air inlet 55 to form the air flow inside and outside the additive injection path 36. As a result, the fuel remaining in the additive injection path 36 after fuel injection can be removed. Further, the cylindrical member 53 is a guide for the fuel injected as described above, and also functions as a guide for the secondary air S, whereby the secondary air S passes through the additive injection path 36 in every corner. The remaining fuel can be removed.

  Further, the secondary air flows into the additive injection path 36 and the secondary air is discharged to the exhaust path 34, thereby promoting the reaction of hydrocarbons (HC) in the exhaust gas and promoting the activation of the catalyst. Can be made.

  As mentioned above, although this embodiment was described, this invention is not limited to embodiment mentioned above.

  For example, the shutter member 54 and the secondary air introduction port 55 are provided to form the air flow inside and outside the additive injection path 36, but the present invention is not limited to this. Even if only the shutter member 54 is provided without providing the secondary air introduction port 55, the injection of the injector 35 is completed if the partition wall 51 protrudes into the exhaust path 34 and the shutter member 54 faces the exhaust path 34. If the shutter member 54 is later opened, a part of the exhaust gas can be introduced into the additive injection path 36, and this exhaust gas again flows into the exhaust path 34 through the passage port 52. The fuel staying in the injection path 36 can be discharged to the exhaust path 34. However, the case where the flow of air inside and outside the additive injection path 36 is formed using secondary air is preferable because deposit generation can be further suppressed.

  For example, although the cylindrical tubular member 53 is provided in the above-described embodiment, the shape is not limited to this, and the shape is not limited as long as the injected fuel can be guided. In addition, the tubular member 53 functions as a guide for secondary air in the above-described embodiment, but a guide member for secondary air may be provided separately. Even in this case, the shutter member 54 and the secondary air introduction port 55 are preferably provided at positions facing each other across the guide member. Further, even if only the partition wall portion 51 is provided without providing the cylindrical member 53, the fuel is less likely to flow than in the case shown in FIG. preferable.

  Further, in the above-described embodiment, as the exhaust purification device 10, the exhaust pipe 12 is provided with the oxidation catalyst 31 and the NOx trap catalyst 32, which are exhaust purification catalysts, and the DPF 33, which is an exhaust purification filter, from the upstream side. In the above example, the NOx trap catalyst 32 and the DPF 33 are arranged in this order. However, the arrangement and types of the exhaust purification catalyst and the exhaust purification filter are not particularly limited.

  In the above-described embodiment, the NOx trap catalyst that decomposes (reduces) NOx using fuel (light oil) as a reducing agent is exemplified as the exhaust gas purification catalyst that decomposes (reduces) NOx, but is not limited thereto. For example, a so-called SCR (Selective Catalytic Reduction) that selectively adsorbs NOx in exhaust gas to a catalyst and injects ammonia or urea as a reducing agent from an injector to decompose (reduce) NOx may be used.

  In the present embodiment, the present invention is applied to a system that supplies fuel to the oxidation catalyst 31, but the present invention can also be applied to a system that supplies fuel to a NOx trap catalyst provided in an exhaust pipe. In this case, the fuel can be appropriately introduced into the NOx trap catalyst from the fuel injection valve installed in the exhaust pipe upstream of the NOx trap catalyst, and NOx and SOx stored in the NOx trap catalyst are efficiently reduced and removed. be able to. In addition to fuel, the present invention can also be applied to a system in which urea water (reducing agent) and other additives are injected into the exhaust pipe.

  INDUSTRIAL APPLICABILITY The present invention can be used in an apparatus that uses an exhaust purification device that removes (deletes) substances such as NOx from exhaust gas, for example, in the automobile manufacturing field.

DESCRIPTION OF SYMBOLS 10 Exhaust purification apparatus 11 Engine 12 Exhaust pipe 27 Turbocharger 31 Oxidation catalyst 32 NOx trap catalyst 34 Exhaust path 35 Injector 36 Additive injection path 41 Upstream member 42 Catalyst holding member 43 Fixing member 44 Inlet 45 Outlet 51 Partition part 52 Opening 54 Shutter member 55 Secondary air inlet

Claims (5)

An exhaust passage connected to the exhaust port of the engine, an exhaust purification catalyst provided in the exhaust passage, an additive injection passage communicating with the exhaust passage upstream of the exhaust purification catalyst in the exhaust passage, An injector for injecting the additive into the additive injection path and supplying the additive to the exhaust gas purification catalyst;
A partition member provided in the exhaust passage so as to be opposed to the injector and spaced from the additive injection passage, and having a passage through which the additive injected from the injector passes, and the partition member and the addition A shutter member provided in a gap with the agent injection path, and isolating the additive injection path from the exhaust path,
The shutter member is openable and closable, and is opened when the additive is not injected from the injector, and performs scavenging between the additive injection path and the exhaust path. The additive injection path is provided with a secondary air introduction path for introducing secondary air into the additive injection path,
2. The exhaust emission control device according to claim 1, wherein when the shutter member is in an open state, the secondary air is introduced into the additive injection passage from the secondary air introduction passage.   The exhaust emission control device according to claim 2, wherein a guide member is provided in the exhaust passage to guide and send the secondary air introduced from the secondary air introduction passage to the injector side. .   The exhaust emission control device according to claim 3, wherein the shutter member and the secondary air introduction path are provided at positions facing each other with the guide member interposed therebetween. A tubular member extends toward the injector side of the partition member,
The hollow portion of the cylindrical member communicates with the passage opening, and the opening area of the passage opening of the hollow portion is configured to become smaller toward the injector side. The exhaust emission control device according to any one of 4.