JP5041168B2 - 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 emitted from engines mounted on automobiles, particularly diesel engines, carbon monoxide (CO), hydrocarbons (HC), nitrogen oxides (NOx), etc., particulate matter (PM: Particulate) Matter) 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.

  A so-called deposit is gradually accumulated on the front end surface of the injector and the periphery thereof, which may cause a problem that the reducing agent cannot be satisfactorily supplied from the injector to the exhaust passage. 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 on the tip surface of the injection and the periphery thereof, the nozzles of the injector may be clogged, and the reducing agent may not be satisfactorily supplied 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, the tip end face of the injector is arranged at a position away from the exhaust path, and the temperature rise of the injector can be suppressed to some extent. Therefore, deposit accumulation on the tip surface of the injector can be suppressed, but deposits accumulate on the inner wall surface of the communication path. If deposits accumulate on the inner wall surface of the communication passage, the passage of the reducing agent is narrowed, and there is a possibility that the reducing agent cannot be supplied satisfactorily to the exhaust passage.

  Here, when spray is emitted from the injection hole, air is injected from the injection port to prevent the spray from the injection hole from colliding with the inner wall surface of the cylindrical tube by the air expanding in a skirt shape. (For example, refer to Patent Document 3).

JP-A-2005-214100 JP 2004-044483 A JP 2005-180371 A

  By employing the technique described in Patent Document 3 in the exhaust gas purification device, it is possible to prevent the additive (reducing agent) from adhering to the inner wall surface of the communication path described above. Further, depositing deposits can be suppressed by preventing the reducing agent serving as a binder from adhering to the inner wall surface of the communication path.

  However, when such a technique is employed in the exhaust purification device, there is a possibility that the above-described filter regeneration process and catalyst reduction process may not be performed satisfactorily. That is, when the additive is injected from the injector and supplied to the exhaust passage, air is also supplied to the exhaust passage at the same time, so that there is a possibility that the exhaust gas necessary for NOx purge, S purge, etc. cannot be enriched, for example. .

  Further, if the amount of air supplied to the exhaust passage is too large, the additive and air become excessive in the catalyst, and there is a risk that noble metal may be deteriorated or melted due to excessive heating of the catalyst. Conversely, if the amount of air supplied to the catalyst is too large, the catalyst is cooled, and the catalytic reaction may be reduced.

  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 capable of suppressing deposit accumulation on the inner wall surface of the communication path while maintaining an excellent exhaust air-fuel ratio. To do.

A first aspect of the present invention that solves the above problems includes an exhaust purification catalyst interposed in an exhaust passage of an engine, and a communication that is disposed upstream of the exhaust purification catalyst and communicates with the exhaust passage. An injector that injects the additive into the exhaust passage through the passage; and a supply passage that is arranged around the injector and communicates with an injection port that opens to the communication passage and supplies air to the communication passage. In addition , when the pressure in the intake pipe on the downstream side of the throttle valve is larger than a predetermined pressure, introducing means for introducing air from the supply path to the communication path at a timing when the additive is injected from the injector; An air-fuel ratio detecting means for detecting an exhaust air-fuel ratio on the downstream side of the exhaust purification catalyst, and so that the exhaust air-fuel ratio becomes a preset target value during a period when air is introduced into the communication path, Adjusting means for relatively adjusting the amount of additive injected from the injector and the amount of air introduced into the communication path based on the detection result of the air-fuel ratio detecting means; In the exhaust purification system.

  In the first aspect, the exhaust air-fuel ratio is adjusted to the target value in a state where air is introduced into the communication path. Therefore, it is possible to satisfactorily carry out the reduction treatment of the exhaust purification catalyst, and it is possible to suppress deposit accumulation.

  In the second aspect of the present invention, the adjustment means controls the amount of additive injected from the injector or the introduction means to increase or decrease at least one of the amount of air supplied to the communication path. There exists in the exhaust emission control device of the 1st aspect characterized by these.

  In the second aspect, the exhaust air-fuel ratio can be adjusted relatively easily to the target value. It should be noted that the exhaust air-fuel ratio can be more reliably set to the target value by adjusting the injection amount of the additive from the injector that is relatively easy to control.

  In the present invention, even when air is introduced into the communication path, the amount of additive injected from the injector and the amount of air introduced into the communication path so that the exhaust air-fuel ratio becomes the target value. Was adjusted relatively. That is, the exhaust air / fuel ratio is substantially always maintained at the target value. Therefore, an appropriate amount of additive can be injected from the injector based on the exhaust air-fuel ratio, and an appropriate amount of air can be introduced from the injection port into the communication path. Therefore, the reduction treatment of the exhaust purification catalyst can be carried out satisfactorily, and deposit accumulation on the inner wall surface of the communication path can also be suppressed.

  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, 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 37 becomes an oxidizing atmosphere, and the NOx trap catalyst 37 only adsorbs NOx. NOx that has been released is not decomposed (reduced). 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 stores sulfur oxide (SOx) in the same manner as nitrogen oxide (NOx), and is decomposed (reduced) at a predetermined timing.

  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 air-fuel ratio sensor (air-fuel ratio detection means) 40 for detecting the oxygen concentration in the exhaust gas is provided in the vicinity of the upstream side of the DPF 38. In the present embodiment, the air-fuel ratio sensor 40 is also provided in the vicinity of the upstream side of the oxidation catalyst 36.

  The vehicle is provided with an electronic control unit (ECU) (not shown). The ECU includes an input / output device, a storage device that stores a control program, a control map, and the like, a central processing unit, timers and counters. Is provided. 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 first 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.

  Further, the mounting member 60 is formed with an injection port 64 that opens to the communication passage 61 and an air passage 65 that communicates with the injection port 64 around the vicinity of the end of the mounting hole 62 on the communication path 61 side. One end of the air passage 65 opens in the outer peripheral surface of the mounting member 60 and is provided in a ring shape around the mounting hole 62. The injection port 64 is also continuously provided around the mounting hole 62 as in the air passage 65.

  One end side of a supply pipe (supply path) 80 is connected to the air passage 65 formed in the mounting member, and the other end side of the supply pipe 80 is connected to the intake pipe (intake passage) 22. For example, the supply pipe 80 is connected to the intake pipe 22 between the turbocharger 27 and the throttle valve 29. The supply pipe 80 may be connected to any position of the intake pipe 22 as long as it is between the turbocharger 27 and the throttle valve 29, but the intake pipe 22 between the intercooler 28 and the throttle valve 29. It is preferable that it is connected to.

  Here, the supply pipe 80 is provided with a check valve 81 which is a check valve that restricts the flow of air toward the intake pipe 22. The check valve 81 is provided to reliably prevent the backflow of the exhaust gas. However, in the configuration of the present embodiment, the exhaust gas rarely flows back, so it does not necessarily have to be provided. . Further, the supply pipe 80 is provided with an opening / closing valve 82 (introduction means) that introduces air into the communication passage 61 at a timing when the supply pipe 80 is opened and closed and fuel is injected from the injector 50. That is, when the on-off valve 82 is opened at the timing when fuel is injected from the injector 50, a part of the air (intake air) flowing through the intake pipe 22 is supplied to the supply pipe by the internal pressure difference between the intake pipe 22 and the exhaust pipe 12. 80 is supplied to the communication passage 61 through the air passage 65 and the injection port 64. The on-off valve 82 is constituted by, for example, a solenoid valve.

  By introducing air into the communication path 61 from the injection port 64 in this way, when the fuel is injected from the injector 50 into the communication path 61, the periphery of the injected fuel is introduced from the injection port 64. Covered with spilled air. That is, the fuel injected from the injector 50 and the inner peripheral surface of the communication path 61 are blocked by a so-called air curtain. Therefore, it is possible to prevent the fuel from adhering to the inner wall surface of the communication path 61 and to suppress deposits on the inner wall surface of the communication path 61 using the fuel as a binder.

  Here, the direction of the injection port 64 may be a direction that does not hinder the supply of fuel from the injector 50 to the exhaust pipe 12, but the inside of the communication path 61 is more than the axial direction of the injector 50 (vertical direction in FIG. 2). It is preferably formed in a direction inclined to the wall surface side. In particular, the direction of the injection port 64 is preferably the direction along the outer shape of the fuel 100 injected from the injector 50. Accordingly, it is possible to effectively prevent the fuel from adhering to the inner wall surface of the communication path 61 without hindering the supply of fuel from the injector 50 to the exhaust pipe 12.

  By the way, when the fuel is injected from the injector 50 as described above, if the air is introduced into the communication passage 61 from the injection port 64, the exhaust air-fuel ratio may become leaner than a desired value. Therefore, in the present invention, as described in detail below, when air is introduced into the communication passage 61 from the injection port 64, the amount of fuel injected from the injector 50 and the amount of air supplied to the communication passage 61 are Was adjusted relatively.

  FIG. 3 is a flowchart illustrating an example of a control method for the exhaust gas purification apparatus according to the first embodiment. As shown in FIG. 3, it is first determined in step S11 whether or not a condition for injecting fuel from the injector 50 (exhaust fuel addition start condition) is satisfied. For example, it is determined whether a condition for performing NOx purge, S purge, DPF regeneration, or the like is satisfied. If such an exhaust fuel addition start condition is not satisfied (step S11: No), the fuel is not injected from the injector 50, and the air is not introduced from the injection port 64, so the processing is ended as it is.

  On the other hand, when the exhaust fuel addition start condition is satisfied (step S11: Yes), the exhaust fuel addition is started in step S12. That is, fuel injection by the injector 50 is started. Next, in step S13, the on-off valve 82 of the supply pipe 80 is opened, and a part of the air (intake air) flowing through the intake pipe 22 is introduced into the communication path 61 through the supply pipe 80, the air passage 65 and the injection port 54. (Introduction means)

  Next, it is determined in step S14 whether or not the air-fuel ratio (exhaust air-fuel ratio) λ of the exhaust gas detected by the air-fuel ratio sensor (air-fuel ratio detecting means) 40 is a preset target value. Here, when the exhaust air-fuel ratio λ is not the target value (step S14: No), the amount of additive injected from the injector 50 and the communication path 61 are supplied so that the exhaust air-fuel ratio λ becomes the target value. The relative air amount is adjusted (adjustment means). Specifically, it is next determined whether or not the exhaust air / fuel ratio λ, which is the detection result of the air / fuel ratio detecting means, is larger than the target value (step S15). That is, in step S15, it is determined whether the exhaust air-fuel ratio λ is lean or rich with respect to the target value.

  If the exhaust air / fuel ratio λ is larger than the target value, that is, if the exhaust air / fuel ratio λ is leaner than the target value (step S15: Yes), the exhaust air / fuel ratio λ is introduced into the communication path 61 in step S16. The amount of air is relatively decreased to enrich the exhaust air / fuel ratio λ so as to reach the target value. In the present embodiment, the air amount is relatively decreased by increasing the fuel injection amount by the injector 50 so that the exhaust air-fuel ratio λ becomes the target value.

  On the other hand, when the exhaust air-fuel ratio λ is smaller than the target value in step S15, that is, when the exhaust air-fuel ratio λ is richer than the target value (step S15: No), the communication passage 61 is entered in step S17. The amount of air to be introduced is relatively increased to make the exhaust air / fuel ratio λ leaner to reach a target value. In the present embodiment, the amount of fuel injected by the injector 50 is decreased in step S17 to relatively increase the air amount so that the exhaust air-fuel ratio λ becomes the target value.

  Thus, by relatively adjusting the amount of additive injected from the injector 50 and the amount of air introduced into the communication passage 61, the exhaust air-fuel ratio λ can be substantially always set to the target value. For example, the exhaust gas necessary for the NOx purge can be reliably enriched. Further, the fuel and air are excessively supplied to the catalyst, so that it is possible to prevent the precious metal from being deteriorated or melted due to an excessive temperature rise. Furthermore, it is possible to prevent the problem that the temperature of the catalyst is lowered and the catalytic reaction is stopped due to excessive supply of air to the catalyst.

  Further, in the present embodiment, the amount of air is relatively increased or decreased by controlling the fuel injection amount by the injector 50, so that the exhaust air-fuel ratio λ can be adjusted relatively easily to the target value. . Of course, the amount of air introduced into the communication path 61 may be increased or decreased. As a method for adjusting the air amount, for example, the duty ratio and pulse width of the on-off valve 82 may be appropriately controlled.

  Thereafter, in step S18, it is determined whether or not an exhaust fuel addition end condition is satisfied. Here, when the exhaust fuel addition end condition is not satisfied (step S18: No), the process returns to step S14 and the above-described processing is repeated. When the exhaust fuel addition end condition is satisfied (step S18: Yes), the fuel addition by the injector 50 is ended in step S19, and the open / close valve 82 is closed in step S20 to introduce air into the communication passage 61. Stop and end the series of processing.

  In the present embodiment, the supply pipe 80 is connected to the intake pipe 22 on the upstream side of the throttle valve 29. However, the supply pipe 80 is on the downstream side 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.

  However, when the supply pipe 80 is connected to the intake pipe 22 on the downstream side of the throttle valve 29 in this way, the pressure in the intake pipe 22 may vary depending on the operation state (for example, the opening degree of the throttle valve 29). May be lower than the internal pressure. For this reason, when the supply pipe 80 is connected to the intake pipe 22 on the downstream side of the throttle valve 29, for example, as described in detail below, it is necessary to perform the above-described processing in consideration of the backflow of exhaust gas. is there.

  FIG. 4 is a flowchart illustrating an example of a control method for the exhaust gas purification apparatus according to the present embodiment. Note that the same steps as those in the flowchart of FIG. 3 are denoted by the same reference numerals, and redundant description is omitted. As shown in FIG. 4, it is first determined in step S11 whether or not an exhaust fuel addition start condition is satisfied. If the exhaust fuel addition start condition is not satisfied (step S11: No), fuel is injected from the injector 50. In addition, since air is not introduced from the injection port 64, the processing is ended as it is. On the other hand, when the exhaust fuel addition start condition is satisfied (step S11: Yes), the exhaust fuel addition is started in step S12.

  Next, in step S31, it is determined 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. That is, in step S31, it is determined whether or not a condition that the exhaust gas does not flow backward 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.

  And when it determines with the pressure P of the intake manifold 21 being larger than the predetermined pressure P1 by step S31 (step S31: Yes), the process of step S13-step S18 mentioned above is performed. On the other hand, when it is determined in step S31 that the pressure P of the intake manifold 21 is equal to or lower than the predetermined pressure P1 (step S31: No), normal exhaust fuel addition control is performed (step S32), and the process proceeds to step S18. Transition. Note that when the normal exhaust fuel addition control is performed in step S32, the on-off valve 82 may be open. In that case, the on-off valve 82 is closed and the normal exhaust fuel addition control is performed.

  In step S18, it is determined whether an exhaust fuel addition end condition is satisfied. Here, when the exhaust fuel addition end condition is not satisfied (step S18: No), the process returns to step S31 and the above-described processing is repeated. When the exhaust fuel addition end condition is satisfied (step S18: Yes), the fuel addition by the injector 50 is ended in step S19, and the open / close valve 82 is closed in step S20 to end the series of processes.

  In such a control method, even when the supply pipe 80 is connected to the intake pipe 22 on the downstream side of the throttle valve 29, the exhaust gas can be prevented from flowing back through the supply pipe 80.

(Other embodiments)
Although the embodiment of the present invention has been described above, the present invention is not limited to this embodiment. For example, although the exhaust air / fuel ratio is adjusted by increasing / decreasing the fuel injection amount by the injector 50, the exhaust air / fuel ratio may be adjusted by controlling the on-off valve 82 provided in the supply pipe 80, or both (injector 50 and The on-off valve 82) may be adjusted in combination. Further, for example, in the above-described embodiment, an open / close valve is provided in the supply pipe 80 as an introducing means for introducing air into the communication passage 61 at the timing when fuel is injected from the injector 50. If air can be introduced into 61, the structure will not be specifically limited.

  Further, for example, in the above-described embodiment, the configuration in which the supply pipe 80 is connected to the intake pipe 22 is illustrated, but of course, as long as the air can be supplied to the communication path 61 via the supply pipe 80, it is not always necessary. The supply pipe 80 need not be connected to the intake pipe 22. That is, air may be introduced into the communication path 61 from other than the intake pipe 22 via the supply pipe 80.

  In the above-described embodiment, the NOx trap catalyst for decomposing (reducing) NOx using fuel (light oil) as a reducing agent is exemplified as the exhaust purification catalyst for decomposing NOx and S. However, the present invention is not limited to this. Alternatively, it may be a so-called SCR (Selective Catalytic Reduction) that selectively adsorbs NOx in the exhaust gas to the catalyst and injects ammonia or urea as a reducing agent from the injector to decompose (reducing) NOx.

  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. FIG. 3 is an enlarged cross-sectional view showing a main part of the exhaust emission control device according to the first embodiment. 2 is a flowchart illustrating an example of a control method for the exhaust gas purification apparatus according to the first embodiment. 2 is a flowchart illustrating an example of a control method for the exhaust gas purification apparatus according to the first embodiment.

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 Air-fuel ratio sensor 50 Injector 60 Mounting member 61 Communication path 62 Mounting hole 63 Cooling water path 64 Injection port 65 Air path 70 Fixing member 80 Supply pipe (supply path)
81 Check valve 82 Open / close valve

Claims (2)

An exhaust purification catalyst interposed in an exhaust passage of an engine, and an injector that is disposed upstream of the exhaust purification catalyst and injects an additive into the exhaust passage through a communication passage communicating with the exhaust passage And a supply path that is arranged around the injector and communicates with an injection port that opens to the communication path and supplies air to the communication path, and
Introducing means for introducing air from the supply path to the communication path at a timing when the additive is injected from the injector when the pressure in the intake pipe on the downstream side of the throttle valve is greater than a predetermined pressure ;
Air-fuel ratio detection means for detecting the exhaust air-fuel ratio on the downstream side of the exhaust purification catalyst;
The amount of additive injected from the injector based on the detection result of the air-fuel ratio detection means so that the exhaust air-fuel ratio becomes a preset target value during the period when air is introduced into the communication passage Adjusting means for relatively adjusting the amount of air introduced into the communication path;
An exhaust emission control device comprising: The said adjustment means controls the quantity of the additive injected from the said injector, or the said introduction means, and increases / decreases at least any one of the air quantity supplied to the said communicating path, The Claim 1 characterized by the above-mentioned. Exhaust purification equipment.

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