JP5115734B2 - Exhaust purification device - Google Patents

Description

  The present invention relates to an exhaust purification device that purifies exhaust gas discharged from an engine.

  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, for example, a three-way catalyst for decomposing (reducing, etc.) the pollutants and a particulate filter for capturing PM in an exhaust passage through which exhaust gas discharged from the engine passes. Etc., so that the exhaust gas is purified and released into the atmosphere.

  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 regeneration processing, a heating device is provided in the particulate filter, and PM is burned and removed by heating. However, fuel (light oil) is added to the oxidation catalyst provided upstream of the particulate filter. A method is also proposed in which a hydrocarbon-based liquid such as) is introduced to cause an exothermic reaction and the particulate filter is regenerated by this heat.

  In diesel engines, nitrogen oxides (NOx) are particularly likely to be generated. For this reason, in order to efficiently decompose NOx in exhaust gas, many so-called NOx trap catalysts that decompose and reduce NOx by repeatedly adsorbing and reducing NOx, for example, are often used in diesel engines. ing.

  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, in general, fuel (light oil) or the like is supplied as a reducing agent into the exhaust passage so as to be supplied to the NOx trap catalyst. For example, there is one in which fuel is injected into an exhaust passage by an injector provided in an exhaust pipe, and exhaust gas mixed with the fuel is supplied to a NOx trap catalyst (see, for example, Patent Document 1).

Since NOx trap catalyst also adsorbs sulfur oxide (SOx) together with NOx, fuel (reducing agent) is supplied to the NOx trap catalyst to raise the temperature of the NOx trap catalyst, thereby decomposing (reducing) SOx. Things are also done.
JP-A-2005-214100 JP 2004-044483 A

  There is a possibility that so-called deposits gradually accumulate on the tip surface of the injector and the periphery thereof, and problems such as nozzle clogging may occur. Specifically, the tip surface of the injector nozzle that injects a reducing agent such as fuel into the exhaust passage is exposed in the exhaust passage and exposed to high-temperature exhaust gas. It becomes relatively hot. For this reason, when the reducing agent (for example, fuel) injected from the injector adheres to the tip end surface of the injector, the volatile component of the attached reducing agent evaporates and the remaining component is denatured and gradually accumulates as deposit. Further, the adhering reducing agent becomes a binder, soot in the exhaust gas adheres and gradually accumulates as a deposit. If deposits accumulate in the nozzles of the injectors in this way, clogging may occur and the reducing agent may not be supplied satisfactorily to the exhaust passage.

  Further, for example, there is an arrangement in which an injection space (communication path) communicating with the exhaust passage is provided, and the reducing agent is injected into the exhaust passage through the injection space (see, for example, Patent Document 2). . When the communication path is provided in this way, deposits may accumulate not only on the front end surface of the injector but also around the injector, that is, on the inner wall of the communication path. If deposits accumulate on the inner wall of the communication passage, the passage of the reducing agent narrows, and there is a possibility that the reducing agent cannot be supplied satisfactorily to the exhaust passage.

  When deposits are accumulated in this way, it is necessary to perform a maintenance operation for removing the deposited deposits by removing the injector. To remove the injector, it is necessary to remove the mounting member to which the injector is attached, the reducing agent (fuel) pipe attached to the injector, the cooling water pipe around it, etc. Work requires considerable effort.

  The present invention has been made in view of such circumstances, and an object of the present invention is to provide an exhaust emission control device that suppresses deposit accumulation on the tip surface of an injector and the inner wall surface of a communication path.

A first aspect of the present invention that solves the above problem is an engine exhaust purification device that includes a turbocharger and an EGR passage that communicates with an intake passage, and is disposed downstream of the turbocharger in the exhaust passage. An exhaust purification catalyst to be mounted, a communication passage that is disposed upstream of the exhaust purification catalyst and communicates with one end side of the exhaust passage, and is fixed with a tip end surface exposed in the communication passage , An injector for injecting an additive into the exhaust passage through the communication passage; one end side communicating with the communication passage and the other end side connected to an intake passage between the turbocharger and the EGR passage; A supply path for supplying air to the communication path, and the supply path is connected to an intake path between the turbocharger and a throttle valve, A control valve for controlling the flow of air in the supply passage, and a check valve for preventing a back flow to the intake passage side are provided on the communication passage side of the control valve, and communicates with the other end side of the communication passage. A mounting member having a mounting hole to which the injector is mounted; one end of the supply path connected to the mounting hole; and one end of the supply path connected to a position offset from the center of the mounting hole It is in the exhaust emission control device characterized by this.

In the first aspect, air (intake air) is supplied into the communication path via the supply path, so that an additive serving as a binder (adhesive) when deposits are deposited is pushed out to the exhaust path. Further, the injector is cooled by the air supplied to the communication path through the supply path. Therefore, even if the exhaust gas flows into the communication path, soot in the exhaust gas can be prevented from adhering to the inner wall surface of the communication path or the tip surface of the injector and accumulating as a deposit.
Further, since the supply passage is connected to the intake passage between the turbocharger and the throttle valve, the pressure of the intake passage where the supply passage is connected is higher than the pressure of the exhaust passage. Air can be satisfactorily supplied from the supply path to the communication path without backflow.
Further, since the supply path is connected to the intake passage between the intercooler and the throttle valve, the air supplied to the communication path is cooled by the intercooler, so that it is supercharged by the turbocharger. It is possible to suppress the intake air from flowing directly into the control valve in a state where the temperature has risen.
In addition, since the control valve for controlling the air flow is provided in the supply path, air can be supplied to the communication path through the supply path at a desired amount and timing while suppressing the backflow of the exhaust gas. .
Further, since the control valve is provided in the vicinity of the end portion of the supply passage on the intake passage side, damage due to heat of the exhaust gas of the control valve can be suppressed even when the exhaust gas slightly flows backward.
In addition, since a check valve is provided on the communication passage side of the control valve in the supply passage to prevent the backflow to the intake passage side, the control valve is controlled by deposit in order to suppress the exhaust gas from flowing into the control valve. It inhibits that the operation of is inhibited. Damage due to heat of the exhaust gas of the control valve can also be suppressed.
In addition, a mounting member having a mounting hole for mounting the injector is provided, and one end side of the supply path is connected to the mounting hole, so that even when deposit accumulates in the vicinity of the tip end surface of the injector, the mounting hole leads to the communication path. The deposited deposit can be removed by supplying air. In addition, the injector can be effectively cooled by the supplied air.

  In the exhaust emission control device according to the present invention, by supplying air to the communication path through the supply path, the exhaust gas containing the additive remaining in the communication path and the deposited deposit can be discharged to the exhaust path. Therefore, deposits can be suppressed from depositing on the inner wall surface of the communication path, the tip surface of the injector, and the like.

  Hereinafter, embodiments of the present invention will be described in detail.

(Embodiment 1)
FIG. 1 is a diagram showing a schematic 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 interposed.

  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. 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. Along with this, the compressor rotates to suck air from the intake pipe 22 into the turbocharger 27 and pressurize it. An intercooler 28 is disposed in the intake pipe 22 on the downstream side of the turbocharger 27. The air pressurized by the turbocharger 27 is cooled by the intercooler 28 and supplied to each intake port 20 of the engine 11.

  The intake pipe 22 on the downstream side of the intercooler 28 is provided with a throttle valve 29 that opens and closes the intake pipe (intake passage) by driving an electric actuator. Further, an EGR pipe (EGR passage) 30 communicating with the exhaust pipe 12 on the upstream side of the turbocharger 27 is connected to the exhaust pipe 12 on the downstream side of the throttle valve 29. The EGR pipe 30 is provided with an EGR cooler 31, and an EGR valve 32 is provided at a connection portion of the EGR pipe 30 with the intake pipe 22. When the EGR valve 32 is opened, a part of the exhaust gas flowing through the exhaust pipe 12 is cooled by the EGR cooler 31 and then supplied to the intake pipe 22.

  The cylinder head 13 is provided with an electronically controlled fuel injection valve 33 that directly injects fuel into the combustion chamber 17 of each cylinder. Fuel is supplied to the fuel injection valve 33 from the common rail 34. Fuel in a fuel tank (not shown) is supplied to the common rail 34 by a supply pump 35, and fuel is supplied from the supply pump 35 to the common rail 34 at a predetermined pressure according to the rotational speed of the engine 11. In the common rail 34, the fuel is adjusted to a predetermined fuel pressure, and high pressure fuel controlled to the predetermined fuel pressure is supplied from the common rail 34 to the fuel injection valve 33.

  Here, in the exhaust pipe 12 on the downstream side of the turbocharger 27, a diesel oxidation catalyst (hereinafter simply referred to as an oxidation catalyst) 36 and a NOx trap catalyst 37 which are exhaust purification catalysts, and a diesel putty which is an exhaust purification filter. A curative filter (DPF: Diesel Particulate Filter: hereinafter referred to as DPF) 38 is sequentially arranged from the upstream side. As will be described in detail later, an injector that injects fuel (light oil) as a reducing agent (additive) into the exhaust pipe (exhaust passage) 12 in the exhaust pipe 12 between the turbocharger 27 and the oxidation catalyst 36. 50 is provided.

The oxidation catalyst 36 is formed, for example, by 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 36, when exhaust gas flows, 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 36 to occur, the oxidation catalyst 36 needs to be heated to a predetermined temperature or higher, and therefore, the oxidation catalyst 36 may be disposed as close to the engine 11 as possible. preferable. This is because the oxidation catalyst 36 is heated by the heat of the engine 11 and the oxidation catalyst 36 can be heated to a predetermined temperature or higher in a relatively short time even when the engine is started.

The NOx trap catalyst 37 includes, for example, a noble metal such as platinum (Pt) and palladium (Pd) supported on a honeycomb structure carrier formed of a ceramic material, and an alkali metal such as barium (Ba) as an occlusion agent, Alternatively, an alkaline earth metal is supported. The NOx trap catalyst 37 temporarily stores NOx in the oxidizing atmosphere, that is, NO ₂ generated by the oxidation catalyst 36, or NO remaining in the exhaust gas without being oxidized by the oxidation catalyst 36. 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 36 is adsorbed / decomposed (reduced) by the NOx trap catalyst 37, and the remaining NO _{2 that} has not been adsorbed / decomposed is purified by the reaction in the DPF 38. .

  Normally, since the exhaust gas discharged from the engine 11 is normally lean, the inside of the NOx trap catalyst 37 becomes an oxidizing atmosphere, and the NOx trap catalyst 37 decomposes (reduces) the adsorbed NOx only by adsorbing NOx. There is nothing. For this reason, when a predetermined amount of NOx is adsorbed on the NOx trap catalyst 37, fuel (light oil) as an additive is injected from the injector 50 fixed to the exhaust pipe 12 between the turbocharger 27 and the oxidation catalyst 36. It has become so. As a result, the exhaust gas mixed with fuel passes through the oxidation catalyst 36 and is supplied to the NOx trap catalyst 37. The inside of the NOx trap catalyst 37 becomes a reducing atmosphere, and the adsorbed NOx is decomposed (reduced). The NOx trap catalyst 37 also stores and decomposes (reduces) sulfur oxide (SOx) as well as nitrogen oxide (NOx).

  The DPF 38 is, for example, a filter having a honeycomb structure formed of a ceramic material. In the DPF 38, for example, an exhaust gas passage 38a in which an upstream end is opened and a downstream end is closed and a downstream end are provided. Exhaust gas passages 38b opened and closed at the upstream end are alternately arranged. The exhaust gas first flows into the exhaust gas passage 38a 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 38b. The gas flows into the gas passage 38b and flows downstream, and in this process, the 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 38 is decomposed into N ₂ and discharged. In other words, the DPF 38 can purify the exhaust gas and greatly reduce the exhaust amount of PM and NOx. Moreover, the performance of the DPF 38 is regenerated to some extent by burning PM.

Here, since NOx is normally adsorbed by the NOx trap catalyst 37 as described above, the amount of NO _{2 in} the exhaust gas supplied to the DPF 38 is small, and PM is gradually deposited on the DPF 38. When a predetermined amount of PM accumulates in the DPF 38, a predetermined amount of fuel is injected from the injector 50 fixed to the exhaust pipe 12. As described above, when the fuel is mixed with the exhaust gas, the NOx trapped in the NOx trap catalyst 37 is reduced, so that NOx (NO ₂ ) contained in the exhaust gas is not adsorbed by the NOx trap catalyst 37. To the DPF 38. Thereby, the combustion of PM in the DPF 38 is promoted.

  An exhaust temperature sensor 39 is provided in the vicinity of the upstream side of the oxidation catalyst 36, the NOx trap catalyst 37, and the DPF 38, and in the vicinity of the downstream side of the DPF 38, respectively. The temperature of the exhaust gas flowing into the trap catalyst 37 and the DPF 38 and the temperature of the exhaust gas discharged from the oxidation catalyst 36, the NOx trap catalyst 37 and the DPF 38 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 36 and the DPF 38. 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 on which the exhaust emission control device 10 is mounted, based on information from the sensors.

  Here, FIG. 2 is an enlarged cross-sectional view showing a main part of the exhaust gas purification apparatus according to the present embodiment. As shown in FIG. 2, the injector 50 that injects fuel as a reducing agent is arranged in a direction substantially orthogonal to the exhaust pipe (exhaust passage) 12 in this embodiment. That is, the injector 50 is arranged such that its axial direction (vertical direction in FIG. 2) and the direction in which the exhaust gas flows (horizontal direction in FIG. 2) are substantially orthogonal. The injector 50 is mounted on a mounting member 60 fixed to the exhaust pipe 12 and is fixed by a fixing member 70.

  A communication passage 61 whose one end communicates with the exhaust pipe (exhaust passage) 12 is formed at the center of the mounting member 60, and a mounting hole 62 for mounting the injector 50 is formed at the other end of the communication passage 61. Is formed. Further, a cooling water channel 63 that is a cooling water channel is formed around the mounting hole 62.

  The injector 50 is mounted in the mounting hole 62 of the mounting member 60, and is fixed to the mounting member 60 by the fixing member 70 in a state where the distal end surface 52 where the nozzle 51 opens is exposed in the communication path 61. The injector 50 is supplied with fuel in a fuel tank (not shown) by a supply pump 35 that is shared with the fuel injection valve 33. The fixing member 70 is detachably fixed to the mounting member 60 by a fastening member such as a bolt, for example.

  The mounting member 60 is provided with an air passage 64 that communicates the vicinity of the end of the mounting hole 62 on the communication passage 61 side with the outside. That is, in a state where the injector 50 is mounted in the mounting hole 62, a slight gap is formed between the inner peripheral surface of the mounting hole 62 and the outer peripheral surface of the injector 50, and this clearance and the outside are connected to the air passage 64. It is communicated by. The air passage 64 and the intake pipe (intake passage) 11 communicate with each other through a supply pipe (supply path) 80. For example, in the present embodiment, one end side of the supply pipe (supply path) 80 is connected to the air passage 64, and the other end side is between the turbocharger 27 and the throttle valve 29. In the present embodiment, the intercooler 28 and the throttle valve 29 are connected. Is connected to the intake pipe 22 between the two.

  In such a configuration, a part of the air (intake air) flowing through the intake pipe 22 is communicated via the supply pipe 80, the air passage 64, and the mounting hole 62 due to the internal pressure difference between the intake pipe 22 and the exhaust pipe 12. Supplied in. Then, the tip of the injector 50 is cooled by the air that passes through the mounting hole 62 and is supplied to the communication passage 61. Therefore, even if the exhaust gas enters the communication path 61, the temperature rise of the injector 50 can be suppressed, and deposits can be suppressed on the front end surface 52 of the injector 50 and its peripheral portion.

  Particularly in the present embodiment, since the supply pipe 80 is connected to the intake pipe 22 on the downstream side of the intercooler 28, relatively cold air cooled by the intercooler 28 is supplied to the supply pipe 80. Therefore, the injector 50 can be cooled more effectively. Of course, the supply pipe 80 may be connected to the intake pipe 22 between the turbocharger 27 and the intercooler 28. Even in this case, since the temperature of the air (intake air) is lower than the temperature of the exhaust gas, the tip of the injector 50 is reliably cooled.

  Further, even when deposits are accumulated in the vicinity of the opening of the mounting hole 62, that is, in the vicinity of the front end surface 52 of the injector 50, the deposit can be blown away by supplying air from the mounting hole 62 to the communication path 61. There is also.

  Here, the air passage 64 may be provided at any position in the radial direction of the mounting hole 62. However, as shown in FIG. 3, the air passage 64 is offset from the center of the mounting hole 62 (off the center line). It is preferable to be connected to (position). As a result, the air supplied from the air passage 64 circulates in the mounting hole 62, and the injector 50 can be cooled more effectively.

  In the present embodiment, the supply pipe 80 is provided with a control valve that controls the flow of air in the supply pipe 80. Specifically, a check valve 81 that is a check valve that restricts the flow of air toward the intake pipe 22, and an open / close valve 82 that opens and closes a supply pipe (supply path), such as a solenoid valve, A supply pipe 80 is provided.

  In the present embodiment, the check valve 81 is provided in order to reliably prevent the exhaust gas from flowing backward. However, since the exhaust gas rarely flows backward, the check valve 81 may not be provided.

  Further, the check valve 81 and the on-off valve 82 as the control valves may be provided at any position of the supply pipe 80, but may be provided near the end of the supply pipe 80 on the intake pipe 22 side. preferable. Since the temperature of the exhaust gas in the exhaust pipe 12 is relatively high, the check valve 81 and the on-off valve 82 are prevented from being affected by the heat of the exhaust gas when provided at a position close to the exhaust pipe 12 side. be able to. This is particularly effective when only the on-off valve 82 is provided without providing the check valve 81. That is, since the on-off valve 82 is provided in the vicinity of the end of the supply pipe 80 on the intake pipe 22 side, the on-off valve 82 reaches the on-off valve 82 and is damaged even if the exhaust gas slightly flows backward. Can be suppressed. Further, when the check valve 81 is provided on the exhaust pipe 12 side from the on-off valve 82, the exhaust gas is prevented from reaching the on-off valve 82, so that deposits adhere to the on-off valve 82 and the operation is caused by heat damage. Defects and the like can be prevented, and control described later can be reliably performed.

  And the on-off valve 82 as a control valve provided in the supply pipe | tube 80 is controlled in this way, and air is supplied to the communicating path 61 at a predetermined timing. As will be described in detail below, for example, after supplying fuel from the injector 50, that is, at a timing when fuel is not injected, air is supplied to the communication path 61 to fill the communication path 61 with air. Thereby, the deposit of the deposit on the front end surface 52 of the injector 50 and the inner wall surface of the communicating path 61 can be further suppressed.

  FIG. 4 is a flowchart illustrating an example of a control method for the exhaust gas purification apparatus according to the present embodiment. As shown in FIG. 4, first, in step S11, it is determined whether or not fuel addition to the exhaust pipe 12 by the injector 50 is performed. Here, when fuel addition is not performed (step S11: No), the on-off valve 82 is opened at step S12. Thereby, a part of the air (intake air) flowing through the intake pipe 22 starts to be supplied into the communication path 61 via the supply pipe 80, the air passage 64 and the mounting hole 62. On the other hand, when the fuel is injected from the injector 50 (step S11: Yes), the process ends without supplying the air into the communication path 61.

  When the on-off valve 82 is opened in step S12 and the supply of air into the communication passage 61 is started, it is next determined whether or not the communication passage 61 is filled with air. A method for determining whether or not the communication path 61 is filled with air is not particularly limited. For example, in this embodiment, a predetermined time T1 until the communication passage 61 is filled with air is checked in advance, and the air in the communication passage 61 is related to the relationship between the time T during which the on-off valve 82 is open and the predetermined time T1. Whether or not is full.

  That is, it is determined whether or not the time T during which the on-off valve 82 is opened exceeds the predetermined time T1 in step S13. When the time T during which the on-off valve 82 is open exceeds the predetermined time T1 (step S13: Yes), the on-off valve 82 is closed at step S14, and the process is terminated.

  By filling the communication path 61 with air in this way, exhaust gas containing fuel injected from the injector 50 is pushed out from the communication path 61 to the exhaust pipe (exhaust path) 12. That is, the exhaust gas containing the fuel that becomes the binder (adhesive) when deposits are deposited can be discharged from the communication path 61. Therefore, even if exhaust gas containing dust enters the communication path 61, it is possible to suppress deposits from depositing on the tip surface 52 of the injector 50 or the inner wall surface of the communication path 61. Of course, since the communication path 61 is filled with air, it is possible to suppress the exhaust gas containing dust from entering the communication path 61 itself.

  In this embodiment, the supply pipe 80 is connected to the intake pipe 22 upstream of the throttle valve 29. However, the supply pipe 80 is downstream of the throttle valve 29, specifically, the throttle valve 29 and the EGR pipe. It may be connected to the intake pipe 22 between 30. When the supply pipe 80 is connected to the intake pipe 22 on the downstream side of the EGR pipe 30, the exhaust gas containing dust that has flowed into the intake pipe 22 from the EGR pipe 30 passes through the supply pipe 80 together with air (intake air). It will be supplied to the communication path 61. For this reason, the supply pipe 80 needs to be connected to the intake pipe 22 upstream of the EGR pipe 30.

  Further, when the supply pipe 80 is connected to the intake pipe 22 on the downstream side of the throttle valve 29, the pressure in the intake pipe 22 depends on the operating state (for example, the opening degree of the throttle valve 29, etc.). May be lower. For this reason, when the supply pipe 80 is connected to the intake pipe 22 on the downstream side of the throttle valve 29, it is necessary to appropriately control the on-off valve 82 in consideration of the backflow of exhaust gas, as will be described in detail below. .

  FIG. 5 is a flowchart illustrating an example of a control method for the exhaust gas purification apparatus according to the present embodiment. As shown in FIG. 5, first, in step S21, it is determined whether or not fuel addition to the exhaust pipe 12 by the injector 50 is performed. Here, when fuel addition is performed (step S21: Yes), the process ends without supplying air into the communication path 61. If fuel addition has not been performed (step S21: No), next, whether or not the pressure P in the intake pipe 22 on the downstream side of the throttle valve 29, specifically, the intake manifold 21, is greater than a predetermined pressure P1. Determine whether. That is, in step S22, it is determined whether or not the condition that the exhaust gas does not flow back through the supply pipe 80 is satisfied. Therefore, the condition for determination does not necessarily need to be the magnitude of the pressure in the intake manifold 21. For example, you may make it determine whether the conditions which do not backflow are satisfy | filled based on a driving | running state with reference to a predetermined | prescribed map.

  If the pressure P of the intake manifold 21 is larger than the predetermined pressure P1 in step S22 (step S22: Yes), the on-off valve 82 is opened in step S23. Thereby, a part of the air (intake air) flowing through the intake pipe 22 starts to be supplied into the communication path 61 via the supply pipe 80, the air passage 64 and the mounting hole 62. If the pressure P of the intake manifold 21 is smaller than the predetermined pressure P1 in step S22 (step S22: No), the process ends without supplying air into the communication path 61. That is, the process ends with the state where the on-off valve 82 is closed in step S25.

  When the opening / closing valve 82 is opened in step S23 and the supply of air into the communication passage 61 is started, it is next determined in step S24 whether or not the time T during which the opening / closing valve 82 is opened exceeds a predetermined time T1. . If the time T during which the on-off valve 82 is open exceeds the predetermined time T1 (step S24: Yes), the on-off valve 82 is closed at step S25, and the process is terminated.

  On the other hand, when the time T during which the on-off valve is opened in step S24 does not exceed the predetermined time T1 (step S24: No), the process returns to step S22 and the pressure P in the intake manifold 21 is greater than the predetermined pressure P1. It is determined whether it is maintained as it is. If the pressure P in the intake manifold 21 is maintained larger than the predetermined pressure P1 (step S22: Yes), the on-off valve 82 is held open (step S23), and the time T during which the on-off valve 82 is open. Is over the predetermined time T1 (step S24: Yes), the on-off valve is closed (step S25), and the process is terminated.

  When the pressure P in the intake manifold 21 is not maintained higher than the predetermined pressure P1 when returning from step S24 to step S22 (step S22: No), the communication path 61 is filled with air. Even in the absence, the on-off valve 82 is closed (step S25), and the process is terminated. As a result, the exhaust gas is prevented from flowing back through the supply pipe 80.

  By controlling the on-off valve 82 as described above, even if the supply pipe 80 is connected to the intake pipe 22 between the throttle valve 29 and the EGR pipe 30, air (intake air) is satisfactorily supplied to the communication path 61. The Accordingly, deposits can be effectively suppressed from being deposited on the tip surface 52 of the injector 50, the inner wall surface of the communication passage 61, and the like.

  In the present embodiment, the on-off valve 82 is controlled to stop the supply of air when the communication passage 61 is filled with air. However, for example, when fuel injection is not performed, the air is always connected. You may make it supply to the channel | path 61. FIG. Thereby, since the air is always filled in the communication path 61 during the period when the fuel injection is not performed, it is possible to more reliably suppress the exhaust gas from flowing into the communication path 61. Therefore, deposit accumulation on the tip surface 52 of the injector 50 and the inner wall surface of the communication passage 61 can be more effectively suppressed. However, in this case, it is necessary to appropriately determine the flow rate of the air supplied into the communication path 61 in consideration of the influence of the air-fuel ratio on the feedback control. That is, it is preferable to reduce the flow rate of air as much as possible.

(Embodiment 2)
FIG. 6 is a cross-sectional view illustrating a main part of the exhaust gas purification apparatus according to the second embodiment.

  The present embodiment is a modification of the mounting member, and the other configuration is the same as that of the first embodiment. Moreover, the same code | symbol is attached | subjected to the same member and the overlapping description is abbreviate | omitted.

  Specifically, as shown in FIG. 6, the mounting member 60 </ b> A according to the present embodiment is provided with a ring-shaped air passage 64 </ b> A around the vicinity of the end of the mounting hole 62 on the communication passage 61 side. An injection port 65 that communicates the air passage 64A and the communication passage 61 is provided. Moreover, the injection port 65 is continuously provided over the periphery of the mounting hole 62 similarly to the air passage 64A.

  In such a configuration of the present embodiment, it is possible to ensure a relatively large injection port 65 that connects the communication passage 61 and the air passage 64A. Therefore, air can be supplied more satisfactorily to the communication passage 61 via the supply pipe 80 and the like, and deposit accumulation on the tip surface 52 of the injector 50 and the inner wall surface of the communication passage 61 is effectively suppressed. Can do.

  Here, the injection port 65 according to the present embodiment is formed in a direction inclined toward the center side of the communication path 61 with reference to the axial direction (vertical direction in the drawing) of the injector 50. In particular, it is preferable that the extension lines of the center line of the injection port 65 intersect with each other in the communication path 61 as indicated by a dotted line in the drawing. In such a configuration, air is continuously supplied from the injection port 65 to the communication passage 61, so that the vicinity of the tip end surface 52 of the injector 50 is closed by the air curtain and the exhaust gas flowing through the injector 50 and the exhaust pipe 12 is shut off. can do. As a result, the contact between the injector 50 and the exhaust gas is suppressed, so that deposits on the tip surface 52 of the injector 50 and the periphery thereof can be further reliably suppressed.

  In the present embodiment, the injection port 65 is continuously provided over the periphery of the mounting hole 62, but of course, the injection port 65 may not be provided continuously over the periphery of the mounting hole 62. . It is sufficient that at least one injection port 65 is provided around the mounting hole 62.

(Other embodiments)
Although the embodiment of the present invention has been described above, the present invention is not limited to this embodiment. For example, in the above-described embodiment, the check valve 81 and the on-off valve 82 as control valves are provided in the supply pipe 80, but only the check valve 81 may be provided. Further, when the supply pipe 80 is connected to the intake pipe 22 on the upstream side of the throttle valve 29, the control valve may not be provided. Further, even when the supply pipe 80 is connected to the intake pipe 22 on the downstream side of the throttle valve 29, the control valve may not be provided if the backflow of the exhaust gas does not become a problem.

  In the above-described embodiment, as an exhaust purification device, an oxidation catalyst and NOx trap catalyst that are exhaust purification catalysts and a DPF that is an exhaust purification filter are connected to an exhaust catalyst (exhaust passage) from the upstream side as an oxidation catalyst, Although an example in which the NOx trap catalyst and the DPF are arranged in the order is given, the arrangement and types of the exhaust purification catalyst and the exhaust purification filter are not particularly limited.

  For example, as shown in FIG. 7A, the NOx trap catalyst 37, the oxidation catalyst 36, and the DPF 38 may be arranged in this order in the exhaust pipe 12 on the downstream side of the turbocharger 27. Further, for example, as shown in FIG. 7B, the NOx trap catalyst 37 and the DPF 38 may be sequentially arranged in the exhaust pipe 12 downstream of the turbocharger 27 without providing the oxidation catalyst. Further, for example, as shown in FIG. 7C, a configuration may be adopted in which only the DPF 38A having a catalytic function is provided without providing the exhaust purification catalyst. That is, only the DPF 38A, which is an exhaust purification filter that also serves as an exhaust purification catalyst, may be provided. In any case, the above-described effects can be obtained by adopting the present invention as long as the configuration has an injector for injecting an additive such as fuel upstream of the exhaust purification catalyst or the exhaust purification filter.

  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 example in which the reducing agent is added as the additive has been described. However, the additive is not limited to the purpose of the reducing action, and if it is added to the exhaust system, for example, by combustion A fuel for the purpose of raising the temperature may be used.

1 is a diagram illustrating a schematic configuration of an exhaust purification device according to Embodiment 1. FIG. 1 is a cross-sectional view showing a main part of an exhaust purification device according to Embodiment 1. FIG. FIG. 3 is an enlarged cross-sectional view showing a main part of the exhaust emission control device according to the first embodiment. 3 is a flowchart illustrating a method for controlling the exhaust purification apparatus according to the first embodiment. 3 is a flowchart illustrating a method for controlling the exhaust purification apparatus according to the first embodiment. FIG. 6 is a cross-sectional view showing a main part of an exhaust purification device according to a second embodiment. It is a schematic block diagram which shows the modification of an exhaust gas purification apparatus.

Explanation of symbols

10 Exhaust purification device 11 Engine 12 Exhaust pipe (exhaust passage)
13 Cylinder Head 14 Cylinder Block 15 Cylinder Bore 16 Piston 17 Combustion Chamber 18 Connecting Rod 19 Crankshaft 20 Intake Port 21 Intake Manifold 22 Intake Pipe (Intake Passage)
23 Intake valve 24 Exhaust port 25 Exhaust manifold 26 Exhaust valve 27 Turbocharger 28 Intercooler 29 Throttle valve 30 EGR pipe (EGR passage)
31 EGR cooler 32 EGR valve 33 Fuel injection valve 34 Common rail 35 Supply pump 36 Oxidation catalyst 37 NOx trap catalyst 38 DPF
39 Exhaust temperature sensor 40 Oxygen concentration sensor 50 Injector 60 Mounting member 61 Communication path 62 Mounting hole 63 Cooling water path 64 Air path 65 Injection port 70 Fixing member 80 Supply pipe (supply path)
81 Check valve 82 Open / close valve

Claims (1)

An exhaust emission control device for an engine having a turbocharger and an EGR passage communicating with an intake passage,
An exhaust purification catalyst interposed downstream of the turbocharger in the exhaust passage;
A communication passage that is disposed upstream of the exhaust purification catalyst and has one end communicating with the exhaust passage ;
An injector that is fixed in a state in which a front end surface is exposed in the communication passage, and injects an additive into the exhaust passage through the communication passage;
A supply path for connecting one end side to the communication path and the other end side being connected to an intake path between the turbocharger and the EGR path to supply air from the intake path to the communication path;
Have
The supply path is connected to an intake passage between the turbocharger and a throttle valve;
The supply path is provided with a control valve for controlling the flow of air in the supply path, and a check valve for preventing a back flow to the intake passage side on the communication passage side of the control valve,
Comprising a mounting member having a mounting hole that communicates with the other end side of the communication path and to which the injector is mounted; one end side of the supply path is connected to the mounting hole;
One end of the supply path is connected to a position offset from the center of the mounting hole.

Images