JP5019069B2 - 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, generally, for example, a three-way catalyst for decomposing (reducing, etc.) the above substances, a particulate filter for capturing PM, etc. in an exhaust passage through which exhaust gas discharged from the engine passes. The exhaust gas is released into the atmosphere in a detoxified state as much as possible.

  In such a particulate filter, since PM accumulates in the filter and the passage resistance increases with use, it is necessary to perform a regeneration process as necessary. As such a regeneration process, a heating device is disposed in the particulate filter, and PM is burned and removed by heating. However, fuel (in the oxidation catalyst provided upstream of the particulate filter is added to the fuel ( There has also been proposed a method in which an exothermic reaction is caused by flowing a hydrocarbon-based liquid such as light oil and the particulate filter is regenerated by this heat.

  In the case of a diesel engine, nitrogen oxide (NOx) is particularly likely to be generated in the exhaust gas. For this reason, in order to efficiently decompose NOx in the exhaust gas, for example, a so-called NOx trap catalyst that repeatedly performs NOx adsorption and reduction to decompose (reduce) NOx is employed in the diesel engine. Yes.

  Since such NOx trap catalyst decomposes (reduces) adsorbed NOx, it is necessary to appropriately supply a reducing agent (additive) from the outside to the NOx trap catalyst. For this reason, it is generally known that fuel (light oil) or the like is supplied to the NOx trap catalyst by being injected into the exhaust passage as a reducing agent (see, for example, Patent Document 1). In patent document 1, the injector is provided in the exhaust pipe through the injection space formed in the direction along the downstream side of the bent portion of the exhaust pipe. The fuel injected from the injector is injected into the flow path in the exhaust pipe through the injection space, and the exhaust gas mixed with this fuel is supplied to the catalyst.

Japanese Unexamined Patent Application Publication No. 2004-044483 (FIG. 1, paragraph 0023, etc.)

  However, according to the above configuration, since the exhaust gas does not flow into the injection space, the injection space is stagnated, and fuel tends to stay in the injection space. The remaining fuel becomes a binder, soot adheres to 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 space is blocked in this way, the supply of the additive becomes insufficient, and there is a risk that the response delay of the air-fuel ratio control will occur or the regeneration process or the decomposition (reduction) process of NOx cannot be performed sufficiently. There is a problem that there is.

  The present invention has been made in view of such circumstances, and an exhaust purification device that prevents deposits from accumulating in the injection space and thereby prevents poor supply of additives into the exhaust passage due to deposits. The purpose is to provide.

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 additive communicating with the exhaust passage upstream of the exhaust purification catalyst. An injection path, and an injector that injects the additive into the additive injection path and supplies the additive to the exhaust gas purification catalyst, and the exhaust path has a downstream side of the additive injection path , The exhaust passage is provided on a wall surface of the exhaust passage, which is provided at a position facing the exhaust gas from the upstream side of the additive injection passage and guides a part of the exhaust gas to flow into the additive injection passage. It comprises the recessed part provided so that it might become convex on the outer side rather than the wall surface of this.

  In the exhaust emission control device of the present invention, by providing the guide portion, a part of the exhaust gas flows into the additive injection path, so that the fuel can be prevented from staying in the additive injection path, and Even if deposits are accumulated in the additive injection path, the deposits can be swept out.

The concave portion is provided on the wall surface of the exhaust passage so as to protrude outward from the wall surface of the exhaust passage, and is provided at a position facing the exhaust gas from the upstream side of the additive injection passage. It is preferable that the exhaust gas is partly guided into the additive injection path. By forming a recess as a guide portion at such a position, a part of the exhaust gas flows into the additive injection path, so that the deposit accumulated in the additive injection path can be easily swept away. It is possible to start.

The injector is provided on the side opposite to the exhaust path of the additive injection path, and the additive injection path is a return portion that suppresses the flow of exhaust gas guided to the additive injection path side to the injector side. It is preferable to provide. By providing the return portion, it is possible to suppress the inflow of the exhaust gas guided to the additive injection path side to the injector side, and the side opposite to the exhaust path of the additive injection path (additive injection It can suppress that exhaust gas contacts the injector provided in the front-end | tip of a path | route.
Further, the additive injection path is provided in communication with the outside of the bent portion of the exhaust path upstream of the exhaust purification catalyst, and the concave portion is the bent section downstream of the additive injection path. It is preferable that the inner wall surface of the bent portion is provided at a position facing the inflow port of the bent portion.
Furthermore, it is preferable that the lower portion of the recess is formed at a position that coincides with the center line of the exhaust gas from the inflow port.

  According to the exhaust emission control device of the present invention, it is possible to sweep out the deposit accumulated in the additive injection path by a part of the exhaust gas, and therefore, into the exhaust passage by the deposit accumulated on the tip surface of the injector. It is possible to prevent poor supply of additives.

  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 port 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 , and NO ₂ remaining in the DPF 33 is decomposed into N ₂ and discharged. That is, the DPF 33 can purify the exhaust gas and greatly reduce PM and NOx emissions. Moreover, the performance of the DPF 33 is regenerated to some extent by burning PM.

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 inlet 44 that is one end on the turbocharger 27 side that opens to the right in FIG. 2, and an outlet 45 that is the other end on the oxidation catalyst 31 side opens downward in FIG. Is configured to be gently bent as a whole. That is, the upstream member 41 is substantially L-shaped when viewed in cross section. Further, the upstream side member 41 is narrow so that the inflow port 44 is narrow and the outflow port 45 is wide in diameter with the catalyst holding member 42.

  The additive injection path 36 is provided outside the bent portion of the exhaust path 34 so as to communicate (open) with the exhaust path 34. That is, in FIG. 2, the additive injection path 36 is arranged on the left wall surface of the exhaust path 34 such that the base end portion where the injector 35 is provided faces in the opposite direction to the inlet 44 of the upstream member 41 (left In the direction). With this configuration, the main part of the exhaust gas flowing in from the inlet 44 and the fuel injected from the injector 35 and passing through the additive injection path 36 are composed of a part where the inner diameter of the upstream member 41 is widened. After mixing at 46, the catalyst contacts the oxidation catalyst 31. 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.

  Specifically, 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 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. While being cooled by the cooling water passage 49 and provided so as not to be exposed directly into the additive injection passage 36 by the holding member 47, it is possible to prevent the injector 35 from being overheated.

  Here, in the present embodiment, the upstream member 41 is provided with a recess 50 as a guide portion that functions as a guide for allowing a part of the exhaust gas to flow into the additive injection path 36. The concave portion 50 is formed by molding on the inner wall surface on the downstream side of the additive injection path 36 of the upstream member 41 and is continuously connected to the additive injection path 36. The recess 50 is preferably formed of a curved surface as shown in FIG. 2 so that the exhaust gas can be smoothly guided. The recess 50 is located at a position facing the exhaust gas (exhaust gas flow) from the upstream side of the additive injection path 36, that is, a position facing the inlet 44, and the center line L1 of the exhaust gas from the inlet 44 And the lower part of the recessed part 50 of the upstream member 41 are formed at a position where they coincide.

  By providing the recess 50, a part of the exhaust gas G1 flowing in from the inlet 44 collides with the recess 50 formed on the wall facing the inlet 44 of the wall surface of the upstream member 41, and the wall surface of the recess 50 The wall surface rises according to the shape and flows into the additive injection path 36. The remaining exhaust gas G2 flows into the mixing section 46 as it is. In this case, since the lower part of the recessed part 50 is installed on the centerline L1 of the main stream of exhaust gas, the exhaust gas is divided into approximately half.

  A part G1 of the exhaust gas flowing into the additive injection path 36 passes through the additive injection path 36 along the inner surface shape of the additive injection path 36 and flows into the mixing unit 46 as it is. A part G1 and the remaining G2 of the exhaust gas flowing into the mixing unit 46 are mixed with fuel in the mixing unit 46, respectively.

  In this way, part of the exhaust gas G1 flows into the additive injection path 36 and flies along the inner surface shape of the additive injection path 36, so that fuel does not stay in the additive injection path 36, In addition, soot and fuel adhering to the inner wall of the additive injection path 36 can be swept out, and it is possible to prevent poor supply of the additive into the exhaust passage due to deposits deposited on the tip surface of the injector. .

  Further, in the present embodiment, the recess 50 is provided so that the lower portion of the recess 50 is on the center line L1, and approximately half of the exhaust gas flows into the additive injection path 36. However, at least the exhaust gas It is only necessary that a part of can be introduced into the additive injection path 36.

  Further, in this embodiment, in order to form the recess 50 in the upstream member 41, the wall surface of the upstream member 41 is formed to be convex outward. However, any aspect can be used as long as the recess 50 can be formed. But you can. For example, if the wall surface constituting the upstream member 41 is sufficiently thick, the recess 50 may be formed by thinning the wall surface.

  Next, in another embodiment shown in FIG. 3, when a part of the exhaust gas G1 is caused to flow into the additive injection path 36 in this way, in order to prevent the hot exhaust gas from coming into contact with the injector 35, A return portion is provided on the protruding portion side of the additive injection path 36. By providing the return portion, the inflow of the exhaust gas guided to the additive injection path 36 side to the injector 35 side is suppressed. That is, by providing the return portion, a part of the exhaust gas G1 that has flowed into the additive injection path 36 is folded back at the return portion and flows out of the additive injection path 36, thereby suppressing the inflow to the injector 35 side, Contact between the injector 35 and the exhaust gas can be prevented. In the embodiment shown in FIG. 3, as the return portion, an extended portion that extends to the vicinity of the center portion of the holding member 47 on the wall surface that forms the additive injection path 36 and is provided with the recess 50. 51 is provided.

  An example of the return portion is one in which a part of the wall surface constituting the additive injection path 36 as shown in FIG. In this case, the exhaust gas can be turned back and flow out from the additive injection path 36 at a position farther away from the injector 35 than in the case shown in FIG. 3, so that the contact between the injector 35 and the exhaust gas can be further increased. Can be prevented.

  Although one embodiment of the present invention has been described above, the present invention is not limited to the above-described embodiment. For example, in the above-described embodiment, as the exhaust purification device 10, the exhaust pipe 12 includes 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 above-described embodiment, the fuel is used as the additive. However, the present invention is not limited to this. For example, a reducing agent for reducing action may be used as long as it is added to the exhaust system.

  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.

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.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Exhaust purification apparatus 11 Engine 12 Exhaust pipe 27 Turbocharger 31 Oxidation catalyst 34 Exhaust path 35 Injector 36 Additive injection path 41 Upstream member 42 Catalyst holding member 43 Fixing member 44 Inlet 45 Outlet 46 Mixing part 47 Holding member 48 Flange Portion 49 Cooling channel 50 Recess 51 Extension portion 52 Projection

Claims (4)

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, and the additive injection An injector for injecting the additive into the road and supplying the additive to the exhaust gas purification catalyst,
The exhaust passage is provided at a position on the downstream side of the additive injection passage and facing the exhaust gas from the upstream side of the additive injection passage, and a part of the exhaust gas is provided in the additive injection passage. An exhaust gas purification apparatus comprising: a concave portion provided on a wall surface of an exhaust passage that is guided to flow into the exhaust passage so as to protrude outward from the wall surface of the exhaust passage. The injector is provided on the opposite side of the exhaust path of the additive injection path,
2. The exhaust emission control device according to claim 1, wherein the additive injection path includes a return portion that suppresses an inflow of exhaust gas guided to the additive injection path side to the injector side. The additive injection path is provided in communication with the outside of the bent portion of the exhaust path upstream from the exhaust purification catalyst,
The said recessed part is an inner wall surface of the said bending part downstream from the said additive injection path, and is provided in the position facing the inflow port of this bending part. Exhaust purification device. The exhaust emission control device according to claim 3 , wherein a lower portion of the recess is formed at a position that coincides with a center line of the exhaust gas from the inflow port.

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