JP2008151103A - Exhaust emission control system of internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a technique for restraining a fuel added to the exhaust gas from turning around into to an air intake passage through an EGR passage in an exhaust emission control system of an internal combustion engine. <P>SOLUTION: The system includes an oxidation catalyst 18 and a filter 19 disposed in an exhaust passage of an internal combustion engine, a plurality of exhaust gas circulation channels 21, 22 formed in the exhaust passage across the oxidation catalyst 18 and the filter 19 in the exhaust gas flow direction, a fuel addition nozzle 11 for adding a fuel to the exhaust gas circulating in the exhaust gas circulation channel 21 on the upstream side of the oxidation catalyst 18, and a low pressure EGR duct 31 for reflux of the exhaust gas circulating in the exhaust gas circulation channel 22 to the air intake passage of the internal combustion engine from the downstream side of the filter 19. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an exhaust gas purification system for an internal combustion engine.

A low pressure EGR passage that takes in a part of exhaust gas as a low pressure EGR gas from an exhaust passage downstream of an exhaust gas purification unit disposed downstream of a turbocharger turbine and returns the low pressure EGR gas to an intake passage upstream of a compressor of the turbocharger. An exhaust gas recirculation device for an internal combustion engine is known (see Patent Document 1).
JP 2000-145501 A JP 2004-092512 A JP 2004-176554 A

  By the way, in order to recover the performance of the exhaust gas purification means, fuel is added to the exhaust gas upstream of the exhaust gas purification means. In some cases, the fuel added to the exhaust gas passes through the exhaust gas purification means and passes through the low pressure EGR passage to the intake passage. The fuel that has entered the intake passage is mixed with the intake air supplied to the internal combustion engine and changes the intake oxygen concentration and the HC concentration. There is.

  An object of the present invention is to provide a technique for suppressing the fuel added to the exhaust from flowing into the intake passage through the EGR passage in the exhaust gas purification system of the internal combustion engine.

In the present invention, the following configuration is adopted. That is,
Exhaust purification means disposed in the exhaust passage of the internal combustion engine;
A plurality of exhaust flow passages formed in an exhaust passage straddling the exhaust purification means in the exhaust flow direction;
Fuel addition means for adding fuel to the exhaust on the upstream side of the exhaust purification means, the exhaust flowing through one of the plurality of exhaust circulation paths;
An EGR passage that recirculates the exhaust flowing through the other of the plurality of exhaust flow passages from the downstream side of the exhaust purification means to the intake passage of the internal combustion engine;
An exhaust gas purification system for an internal combustion engine.

  According to the configuration of the present invention, the exhaust gas containing the fuel added from the fuel addition means flows through one of the plurality of exhaust circulation paths, and the fuel from the fuel addition means passes through the other of the plurality of exhaust circulation paths. Exhaust gas that is not added and contains no fuel flows.

  Since one of the plurality of exhaust flow paths is connected to the outside downstream of the exhaust purification means through the exhaust passage, the exhaust gas containing fuel is released to the atmosphere by the exhaust purification means recovering the performance of the exhaust purification means. Is done.

  On the other hand, the other of the plurality of exhaust flow paths is connected to the EGR passage at the downstream side of the exhaust purification means, so that the exhaust gas not containing fuel is recirculated to the intake passage through the EGR passage. At the time of this recirculation, since the fuel is not included in the exhaust gas, the fuel does not enter the intake passage. Therefore, since it is difficult for fuel to be mixed into the intake air supplied to the internal combustion engine and the intake oxygen concentration or HC concentration of the intake air is difficult to change, even if this intake air is taken in, the torque fluctuation can be suppressed in the internal combustion engine.

  Further, the exhaust gas flowing through the other of the plurality of exhaust gas flow paths contains NOx, but since this exhaust gas is recirculated to the intake passage, NOx is not released into the atmosphere.

  A rectifying plate for partitioning one and the other of the plurality of exhaust flow paths may be provided.

  According to the configuration of the present invention, the exhaust gas can flow through each of the exhaust flow paths without being mixed with one of the plurality of exhaust flow paths.

  The rectifying plate is cylindrical, and one and the other of the plurality of exhaust flow paths may be partitioned into an inner diameter side and an outer diameter side of the rectifying plate.

  According to the configuration of the present invention, the exhaust gas can be divided into the inner diameter side and the outer diameter side of the rectifying plate without being mixed with one and the other of the plurality of exhaust circulation paths, and can be circulated through the respective exhaust circulation paths.

  One of the plurality of exhaust circulation paths may be an inner diameter side of the rectifying plate, and the other of the plurality of exhaust circulation paths may be an outer diameter side of the rectifying plate.

  According to the configuration of the present invention, the exhaust gas containing the fuel flows through the inner diameter side of the rectifying plate, and the temperature rise when the fuel contained in the exhaust gas chemically reacts with the exhaust gas purification device is difficult to be cooled by the outside air. The fall of the bed temperature about the inner diameter side of the current plate can be suppressed.

  A wall surface disposed at the center of the fuel addition means and facing the inlet of one of the plurality of exhaust flow paths on the inner diameter side of the rectifying plate, a convex portion whose center protrudes downstream in the exhaust flow direction. It may be provided in a shape.

  According to the configuration of the present invention, one of the plurality of exhaust circulation paths on the inner diameter side of the rectifying plate is brought close to the fuel addition means, and the fuel added from the fuel addition means is the other of the plurality of exhaust circulation paths. Can be prevented from flowing into

  Further, by adjusting the convex amount of the convex shape of the wall surface, it is possible to adjust the exhaust flow rate to one of the plurality of exhaust flow paths on the inner diameter side of the rectifying plate.

  One of the plurality of exhaust circulation paths may be on the outer diameter side of the rectifying plate, and the other of the plurality of exhaust circulation paths may be on the inner diameter side of the rectifying plate.

  According to the configuration of the present invention, the exhaust gas containing the fuel flows through the outer diameter side of the rectifying plate, and the temperature rise when the fuel contained in the exhaust gas chemically reacts with the exhaust purification means, the exhaust gas on the outer diameter side of the rectifying plate Since the purification means is warmed and the heat is further propagated and the exhaust purification means on the inner diameter side of the rectifying plate is also warmed, a decrease in the bed temperature of the entire exhaust purification means can be suppressed.

  It is good to provide the wind guide means which makes the exhaust which distribute | circulates one side among these exhaust flow paths which are the outer diameter side of the said baffle plate turn.

  According to the configuration of the present invention, the exhaust gas flowing through one of the plurality of exhaust gas flow paths on the outer diameter side of the rectifying plate turns, and the exhaust gas containing fuel can be supplied to the entire outer diameter side of the rectifying plate.

  The fuel addition means may add fuel toward the outer peripheral surface of the rectifying plate upstream of the exhaust purification means.

  According to the configuration of the present invention, the fuel added to the exhaust collides with the outer peripheral surface of the rectifying plate, flows along the outer periphery of the rectifying plate, flows into the exhaust purification means, and is widely distributed on the outer diameter side of the rectifying plate. Can be distributed.

  The exhaust purification means may be composed of two upstream exhaust purification means and two downstream exhaust purification means arranged in series in the exhaust flow direction.

  According to the configuration of the present invention, the two exhaust purification means are arranged, and the exhaust can be purified better.

  The rectifying plate may be provided between the upstream side exhaust purification unit and the downstream side exhaust purification unit.

  According to the configuration of the present invention, the exhaust gas flows through each exhaust flow path between the upstream exhaust gas purification means and the downstream exhaust gas purification means without being mixed with one of the plurality of exhaust flow paths. it can.

  The NOx storage reduction catalyst may be carried on a portion of the exhaust purification means through which one exhaust gas flows.

  According to the configuration of the present invention, the amount of catalyst supported can be reduced because the NOx storage reduction catalyst is not supported on the portion of the plurality of exhaust flow paths of the exhaust gas purification unit where the other exhaust gas flows.

  The pore diameter of the portion of the exhaust gas purification unit where the exhaust gas on the inner diameter side of the rectifying plate circulates may be smaller than the pore diameter of the portion where the exhaust gas on the outer diameter side of the rectifying plate circulates.

  According to the configuration of the present invention, the PM trapping rate on the inner diameter side of the rectifying plate of the exhaust purification means can be increased, and the bed temperature on the inner diameter side of the rectifying plate of the exhaust purification means is unlikely to decrease. The captured PM can be removed efficiently.

  A discharge hole for discharging condensed water may be provided in the rectifying plate on the downstream side of the exhaust purification unit.

  According to the configuration of the present invention, the condensed water accumulated in the other of the plurality of exhaust circulation paths can be discharged from the discharge hole to one of the plurality of exhaust circulation paths, and further discharged from there. Thereby, it can suppress that condensed water flows in into an intake passage via an EGR passage from the other among a plurality of exhaust circulation routes.

  An exhaust throttle valve which is disposed in the exhaust passage downstream of the exhaust purification means and adjusts the flow rate of exhaust gas flowing through one of the plurality of exhaust circulation paths; and downstream of the EGR passage and the exhaust throttle valve A bypass passage connecting between the exhaust passage, and when adding fuel by the fuel addition means, the exhaust throttle valve is controlled to the closed side, and exhaust is sent to the other of the plurality of exhaust flow paths The EGR passage and the bypass passage may be passed through to the exhaust passage.

  According to the configuration of the present invention, when the fuel is added by the fuel addition means, the exhaust can be confined in one of the plurality of exhaust circulation paths by controlling the exhaust throttle valve to the closed side. For this reason, even when the flow velocity of the exhaust gas flowing through the exhaust passage is high, the fuel consumption is reduced by adding the fuel by the fuel addition means, and the air-fuel ratio is reduced in one of the plurality of exhaust circulation paths. Can be suitably rich, or can be suitably raised to a predetermined temperature.

  Further, when the exhaust throttle valve is controlled to the closed side, the flow of exhaust gas is retarded, and the exhaust resistance increases, leading to a decrease in engine output. However, according to the configuration of the present invention, when the exhaust throttle valve is controlled to the closed side, the exhaust is allowed to flow from the other of the plurality of exhaust circulation paths through the EGR passage and the bypass passage to the exhaust passage. As a result, it is possible to suppress a decrease in engine output by suppressing an increase in exhaust resistance without delaying an exhaust flow.

  An opening / closing valve for adjusting a flow rate of exhaust gas flowing through the bypass passage is provided in the bypass passage, and when the fuel is added by the fuel addition means and the exhaust throttle valve is controlled to be closed, the opening / closing valve is opened. It is good to let them.

  When the exhaust throttle valve is controlled to the closed side, the exhaust gas is allowed to flow from the other of the plurality of exhaust circulation paths through the EGR passage and the bypass passage to the exhaust passage. For this reason, it is necessary to open the on-off valve provided in the bypass passage only when the fuel is added by the fuel addition means and the exhaust throttle valve is controlled to the closed side. Therefore, when the fuel is added by the fuel addition means and the exhaust throttle valve is controlled to the closed side, the on-off valve is opened. As a result, when the bypass passage is opened excessively, for example, when fuel addition by the fuel addition means is completed and the exhaust throttle valve is controlled to open, the exhaust gas that has been added and has passed through the exhaust throttle valve flows into the bypass passage. Can be prevented. As a result, the exhaust does not enter the intake passage via the bypass passage and the EGR passage.

  The EGR passage is provided with an EGR valve that adjusts the flow rate of the exhaust gas flowing through the EGR passage, and fuel addition for SOx poisoning recovery processing by the fuel addition means is completed, and the exhaust throttle valve is controlled to open side In this case, while the sulfur component is being discharged from one of the plurality of exhaust circulation passages to the exhaust passage downstream, the EGR valve is closed and the exhaust gas before flowing into the exhaust gas purification means is removed from the internal combustion engine. It is good to recirculate to the intake passage.

  When the fuel addition for SOx poisoning recovery processing by the fuel addition means is completed and the exhaust throttle valve is controlled to open, exhaust containing sulfur components flows into the bypass passage and passes through the bypass passage and the EGR passage. There is a risk of sneaking into the intake passage. However, according to the configuration of the present invention, when the fuel addition for the SOx poisoning recovery process by the fuel addition unit is completed and the exhaust throttle valve is controlled to the open side, the downstream of one of the plurality of exhaust flow paths is downstream. By closing the EGR valve while the sulfur component is discharged to the exhaust passage, it is possible to prevent the exhaust gas containing the sulfur component from flowing into the intake passage from the EGR passage. As a result, the exhaust gas containing the sulfur component does not enter the intake passage via the bypass passage and the EGR passage.

  Further, when the EGR valve is closed, there is a possibility that the amount of EGR gas to be supplied to the internal combustion engine is insufficient. However, according to the configuration of the present invention, when the EGR valve is closed, the amount of EGR gas to be supplied to the internal combustion engine is compensated by returning the exhaust gas before flowing into the exhaust gas purification means to the intake passage of the internal combustion engine. ing. Here, examples of the method of “recirculating the exhaust gas before flowing into the exhaust gas purification means to the intake passage of the internal combustion engine” include an EGR operation using a high-pressure EGR passage and an internal EGR operation.

  According to the present invention, in the exhaust gas purification system for an internal combustion engine, it is possible to suppress the fuel added to the exhaust gas from flowing into the intake passage through the EGR passage.

  Specific examples of the present invention will be described below.

<Example 1>
FIG. 1 is a diagram showing a schematic configuration of an internal combustion engine to which the exhaust gas purification system for an internal combustion engine according to this embodiment is applied and its intake / exhaust system.

  An internal combustion engine 1 shown in FIG. 1 is a water-cooled four-cycle diesel engine having four cylinders 2 that form a combustion chamber together with a piston. The internal combustion engine 1 is mounted on a vehicle. An intake passage 3 and an exhaust passage 4 are connected to the internal combustion engine 1.

  In the middle of the intake passage 3 connected to the internal combustion engine 1, a compressor housing 5a of a turbocharger 5 that operates using exhaust energy as a drive source is disposed. A first throttle valve 6 for adjusting the flow rate of intake air flowing through the intake passage 3 is disposed in the intake passage 3 upstream of the compressor housing 5a. The first throttle valve 6 is opened and closed by an electric actuator. An air flow meter 7 that outputs a signal corresponding to the flow rate of the intake air (fresh air) flowing through the intake passage 3 is disposed in the intake passage 3 upstream of the first throttle valve 6. The air flow meter 7 measures the intake air amount (fresh air amount) of the internal combustion engine 1.

  An intercooler 8 that performs heat exchange between the intake air and the outside air is disposed in the intake passage 3 downstream of the compressor housing 5a. A second throttle valve 9 for adjusting the flow rate of the intake air flowing through the intake passage 3 is provided in the intake passage 3 downstream of the intercooler 8. The second throttle valve 9 is opened and closed by an electric actuator.

  On the other hand, a turbine housing 5 b of the turbocharger 5 is arranged in the middle of the exhaust passage 4 connected to the internal combustion engine 1. An exhaust purification device 10 is arranged in the exhaust passage 4 downstream of the turbine housing 5b.

  The exhaust purification device 10 is provided with a fuel addition nozzle 11 for adding fuel to the exhaust. This fuel addition nozzle 11 corresponds to the fuel addition means of the present invention.

  In addition, an exhaust throttle valve 12 that adjusts the flow rate of the exhaust gas flowing through the exhaust passage 4 is provided in the exhaust passage 4 downstream of the exhaust purification device 10. The exhaust throttle valve 12 is opened and closed by an electric actuator.

  The internal combustion engine 1 is provided with a low pressure EGR device 30 that recirculates (recirculates) part of the exhaust gas flowing through the exhaust passage 4 to the intake passage 3 at a low pressure. The low pressure EGR device 30 includes a low pressure EGR passage 31, a low pressure EGR valve 32, and a low pressure EGR cooler 33.

  The low pressure EGR passage 31 connects the downstream portion of the exhaust purification device 10 and the intake passage 3 upstream of the compressor housing 5a and downstream of the first throttle valve 6. Exhaust gas is fed into the internal combustion engine 1 at low pressure through the low pressure EGR passage 31. In this embodiment, the exhaust gas recirculated through the low pressure EGR passage 31 is referred to as low pressure EGR gas. The low pressure EGR passage 31 corresponds to the EGR passage of the present invention.

  The low pressure EGR valve 32 adjusts the amount of the low pressure EGR gas flowing through the low pressure EGR passage 31 by adjusting the passage sectional area of the low pressure EGR passage 31.

Further, the low-pressure EGR cooler 33 exchanges heat between the low-pressure EGR gas passing through the low-pressure EGR cooler 33 and the engine cooling water of the internal combustion engine 1 to reduce the temperature of the low-pressure EGR gas. Further, the low pressure EGR cooler 33 can also warm the engine cooling water by the low pressure EGR gas when the engine cooling water is at a lower temperature than the low pressure EGR gas.

  On the other hand, the internal combustion engine 1 is provided with a high-pressure EGR device 40 that recirculates a part of the exhaust gas flowing through the exhaust passage 4 to the intake passage 3 at a high pressure. The high pressure EGR device 40 includes a high pressure EGR passage 41 and a high pressure EGR valve 42.

  The high pressure EGR passage 41 connects the exhaust passage 4 upstream of the turbine housing 5b and the intake passage 3 downstream of the compressor housing 5a. Exhaust gas is fed into the internal combustion engine 1 at a high pressure through the high pressure EGR passage 41. In this embodiment, the exhaust gas recirculated through the high pressure EGR passage 41 is referred to as high pressure EGR gas.

  Further, the high pressure EGR valve 42 adjusts the amount of high pressure EGR gas flowing through the high pressure EGR passage 41 by adjusting the passage sectional area of the high pressure EGR passage 41.

  The internal combustion engine 1 configured as described above is provided with an ECU 13 that is an electronic control unit for controlling the internal combustion engine 1. The ECU 13 is a unit that controls the operation state of the internal combustion engine 1 in accordance with the operation conditions of the internal combustion engine 1 and the request of the driver.

  The ECU 13 includes an air flow meter 7, an accelerator opening sensor 15 that outputs an electric signal corresponding to the amount of depression of the accelerator pedal 14 by the driver and can detect the engine load, and a crank position sensor 16 that detects the engine speed. Connected via electric wiring, the output signals of these various sensors are input to the ECU 13.

  On the other hand, the first throttle valve 6, the second throttle valve 9, the fuel addition nozzle 11, the exhaust throttle valve 12, the low-pressure EGR valve 32, and the high-pressure EGR valve 42 are connected to the ECU 13 through electrical wiring. The ECU 13 controls these devices.

  Next, the exhaust emission control device 10 according to the first embodiment will be described with reference to FIG.

  In the exhaust purification device 10, an upstream side oxidation catalyst 18 and a downstream side particulate filter (hereinafter simply referred to as a filter) 19 are disposed surrounded by the outer wall 17. The oxidation catalyst 18 is heated by the fuel added to the exhaust gas. The filter 19 collects particulate matter (PM) in the exhaust gas. The oxidation catalyst 18 corresponds to the upstream side exhaust purification unit of the present invention, and the filter 19 corresponds to the downstream side exhaust purification unit of the present invention. The oxidation catalyst 18 and the filter 19 generally correspond to the exhaust purification means of the present invention. Further, the filter 19 may carry an NOx storage reduction catalyst (hereinafter simply referred to as NOx catalyst) or another catalyst.

  In the exhaust purification device 10, cylindrical rectifying plates 20 a and 20 b are disposed across the oxidation catalyst 18 and the filter 19. The rectifying plates 20 a and 20 b form an inner diameter side exhaust circulation path 21 and an outer diameter side exhaust circulation path 22 in the exhaust purification device 10. Each of the rectifying plates 20a and 20b prevents the exhaust gas from entering and mixing between the inner diameter side exhaust circulation path 21 and the outer diameter side exhaust circulation path 22 so that the exhaust flows through the respective exhaust circulation paths 21 and 22. ing.

  The inner diameter side exhaust circulation path 21 to which fuel is added from the fuel addition nozzle 11 is directly connected to the exhaust path 4 downstream of the filter 19. On the other hand, the outer diameter side exhaust circulation path 22 to which no fuel is added from the fuel addition nozzle 11 is separated from the exhaust passage 4 at the downstream side of the filter 19 by the rectifying plate 20 b and is connected to the low pressure EGR passage 31 connected beyond the outer wall 17. ing.

  Here, the fuel addition nozzle 11 for adding fuel to the exhaust gas upstream of the oxidation catalyst 18 is disposed upstream of the oxidation catalyst 18 in the inner diameter side exhaust circulation path 21. For this reason, when fuel is added from the fuel addition nozzle 11 to the exhaust gas in the inner diameter side exhaust circulation path 21, the temperature of the upstream oxidation catalyst 18 can be raised, and the downstream filter 19 recovers the performance of the filter 19. The PM oxidation removal process can be executed. Such processing for recovering the performance of the filter 19 corresponds to processing for recovering the performance of the exhaust purification means of the present invention.

  The PM oxidation removal process is to add fuel into the exhaust gas from the fuel addition nozzle 11 to oxidize the fuel in the oxidation catalyst 18 and to increase the temperature of the filter 19 by heat generated during the oxidation. This is a process for removing the collected PM.

  In the present embodiment, since the fuel is added only to the inner diameter side exhaust circulation path 21, the temperature rise during oxidation by the fuel added to the exhaust is performed on the inner diameter side of the oxidation catalyst 18 and the filter 19. And the inner diameter side of the oxidation catalyst 18 and the filter 19 becomes a heat insulating layer on the outer diameter side, and is difficult to be cooled by the outside air, so that a decrease in bed temperature is suppressed. Further, the PM oxidation removal process is executed on the outer diameter side of the filter 19 by the propagation of heat from the inner diameter side thereof.

  Since the exhaust purification device 10 is configured as described above, exhaust gas containing fuel added from the fuel addition nozzle 11 circulates in the inner diameter side exhaust circulation path 21, and fuel added to the outer diameter side exhaust circulation path 22. From the nozzle 11, no fuel is added and exhaust without fuel flows.

  Since the downstream side of the filter 19 is connected to the outside through the exhaust passage 4, the exhaust gas containing fuel raises the temperature of the oxidation catalyst 18 and performs PM oxidation removal processing by the filter 19. Released into the atmosphere.

  On the other hand, since the downstream side of the filter 19 is connected to the low pressure EGR passage 31 in the outer diameter side exhaust circulation path 22, the exhaust gas that does not contain fuel flowing through the outer diameter side exhaust circulation path 22 passes through the low pressure EGR passage 31. It returns to the intake passage 3. During this recirculation, the fuel does not enter the intake passage 3 because no fuel is contained in the exhaust gas. Therefore, it is difficult for the fuel to be mixed into the intake air supplied to the internal combustion engine 1 and the intake oxygen concentration or HC concentration of the intake air is difficult to change. Therefore, even if this intake air is taken in, the internal combustion engine 1 can suppress torque fluctuation.

  Further, although the exhaust gas flowing through the outer diameter side exhaust circulation path 22 contains NOx, since this exhaust gas is recirculated to the intake passage 3, NOx is not released to the atmosphere.

<Example 2>
Next, an exhaust emission control device 10a according to Embodiment 2 will be described with reference to FIG. In the present embodiment, the characteristic part of the present embodiment will be described, and the description of the items described in the above embodiment will be omitted.

  In the exhaust purification device 10a, cylindrical rectifying plates 20a and 20b are disposed across the oxidation catalyst 18 and the filter 19. A cylindrical rectifying plate 20 c is also disposed between the oxidation catalyst 18 and the filter 19. The rectifying plates 20a, 20b, and 20c form an inner diameter side exhaust circulation path 21 and an outer diameter side exhaust circulation path 22 in the exhaust purification apparatus 10a. Each of the rectifying plates 20a, 20b, 20c prevents the exhaust from entering and mixing between the inner diameter side exhaust circulation path 21 and the outer diameter side exhaust circulation path 22, and the exhaust flows through each of the exhaust circulation paths 21, 22. I am doing so.

In the present embodiment, since the rectifying plate 20c is also disposed between the oxidation catalyst 18 and the filter 19, it is assumed that exhaust gas enters and mixes between the inner diameter side exhaust circulation path 21 and the outer diameter side exhaust circulation path 22. More can be prevented.

<Example 3>
Next, an exhaust emission control device 10b according to Embodiment 3 will be described with reference to FIG. In the present embodiment, the characteristic part of the present embodiment will be described, and the description of the items described in the above embodiment will be omitted.

  In the exhaust purification device 10b, a NOx catalyst 19a is carried on a portion through which exhaust gas flowing through the inner diameter side exhaust flow path 21 of the filter 19 passes, that is, on the inner diameter side of the filter 19. The NOx catalyst 19a occludes NOx in the exhaust when the oxygen concentration of the exhaust flowing into the NOx catalyst 19a is high, and occludes when the oxygen concentration of the exhaust flowing into the NOx catalyst 19a decreases. Releases NOx. At the time of the release, if a reducing component such as HC or carbon monoxide (CO) is present in the exhaust gas, the NOx released from the NOx catalyst 19a is reduced.

  For this reason, on the inner diameter side of the filter 19, as a process for recovering the performance of the filter 19, in addition to the PM oxidation removal process, a NOx reduction process and a SOx poisoning recovery process can be executed.

  In the NOx reduction process, fuel is added to the exhaust gas in a spike manner from the fuel addition nozzle 11 to enrich the air-fuel ratio of the exhaust gas flowing into the NOx catalyst 19a, and the NOx occluded in the NOx catalyst 19a is released and reduced. It is a process to make.

  In the SOx poisoning recovery process, fuel is added to the exhaust gas in a spike manner from the fuel addition nozzle 11 to oxidize the added fuel in the NOx catalyst 19a, and the catalyst temperature is set to a required temperature (for example, 600 ° C.) by heat accompanying the oxidation reaction. Is a process of releasing and reducing SOx occluded in the NOx catalyst 19a by increasing the air-fuel ratio of the exhaust gas flowing into the NOx catalyst 19a.

  Further, in the PM oxidation removal process, fuel is added not only to the oxidation catalyst 18 but also to the NOx catalyst 19a by adding fuel from the fuel addition nozzle 11 into the exhaust gas, and the filter 19 is heated by the heat generated during the oxidation. The PM collected by the filter 19 can be removed.

  In the present embodiment, since the NOx catalyst 19a is supported only on the inner diameter side of the filter 19, the NOx catalyst is not supported on the portion where the exhaust gas in the outer diameter side exhaust circulation path 22 circulates, that is, on the outer diameter side of the filter 19. The amount of catalyst supported can be reduced.

<Example 4>
Next, an exhaust emission control device 10c according to a fourth embodiment will be described with reference to FIG. In the present embodiment, the characteristic part of the present embodiment will be described, and the description of the items described in the above embodiment will be omitted.

  In the exhaust gas purification apparatus 10 c, the part through which the exhaust gas flowing through the inner diameter side exhaust flow path 21 of the filter 19 passes, that is, the pore diameter of the inner diameter side 19 b of the filter 19 is made smaller than the pore diameter of the outer diameter side of the filter 19. ing.

  In this embodiment, the PM trapping rate on the inner diameter side 19b of the filter 19 can be increased, and the bed temperature on the inner diameter side 19b of the filter 19 is difficult to decrease. it can.

<Example 5>
Next, an exhaust emission control device 10d according to Embodiment 5 will be described with reference to FIG. In the present embodiment, the characteristic part of the present embodiment will be described, and the description of the items described in the above embodiment will be omitted.

  In the exhaust purification apparatus 10d, a discharge hole 23 for discharging condensed water is provided in the rectifying plate 20b on the downstream side of the filter 19.

  In the present embodiment, the condensed water accumulated in the outer diameter side exhaust circulation path 22 can be discharged from the discharge hole 23 to the inner diameter side exhaust circulation path 21 and further discharged from there. Thereby, it can suppress that condensed water flows in into the intake passage 3 through the low diameter EGR channel | path 31 from the outer diameter side exhaust circulation channel | path 22. FIG.

<Example 6>
Next, an exhaust emission control device 10e according to Embodiment 6 will be described with reference to FIG. In the present embodiment, the characteristic part of the present embodiment will be described, and the description of the items described in the above embodiment will be omitted.

  In the exhaust emission control device 10e, a wall surface 17a that is a wall surface in which the fuel addition nozzle 11 is arranged in the center and that faces the inlet of the inner diameter side exhaust flow path 21 that is the inner diameter side of the rectifying plate 20a is centered toward the downstream in the exhaust flow direction. Are provided in a protruding shape.

  In this embodiment, the inlet of the inner diameter side exhaust circulation path 21 and the fuel addition nozzle 11 attached to the convex wall surface 17a are brought close to each other, and the fuel added from the fuel addition nozzle 11 is outside the outer diameter side exhaust circulation path. Outflow to 22 can be suppressed.

  Further, the exhaust flow rate to the inner diameter side exhaust circulation path 21 can be adjusted by adjusting the convex amount of the convex shape of the wall surface 17a.

<Example 7>
Next, an exhaust emission control device 10f according to Embodiment 7 will be described with reference to FIG. In the present embodiment, the characteristic part of the present embodiment will be described, and the description of the items described in the above embodiment will be omitted.

  In the outer diameter side exhaust circulation path 22 to which fuel is added from the fuel addition nozzle 11, the downstream side of the filter 19 is directly connected to the exhaust path 4. On the other hand, the inner diameter side exhaust circulation path 21 to which no fuel is added from the fuel addition nozzle 11 is separated from the exhaust passage 4 at the downstream side of the filter 19 by the rectifying plate 20b and connected to the low pressure EGR passage 31 connected beyond the outer wall 17. Yes.

  Here, a fuel addition nozzle 11 for adding fuel to the exhaust gas upstream of the oxidation catalyst 18 is disposed upstream of the oxidation catalyst 18 in the outer diameter side exhaust circulation path 22. For this reason, when fuel is added from the fuel addition nozzle 11 to the exhaust gas in the outer diameter side exhaust circulation path 22, the temperature of the upstream oxidation catalyst 18 can be raised, and the downstream filter 19 recovers the performance of the filter 19. PM oxidation removal processing can be executed.

In the present embodiment, since the fuel is added only to the outer diameter side exhaust circulation path 22, the temperature rise during oxidation by the fuel added to the exhaust is performed on the outer diameter side of the oxidation catalyst 18 and the filter 19. And the outer-diameter side of the oxidation catalyst 18 and the filter 19 is heated, and these heats propagate to the inner-diameter side, thereby suppressing a decrease in the overall bed temperature of the oxidation catalyst 18 and the filter 19. Further, the PM oxidation removal process is executed on the inner diameter side of the filter 19 by the propagation of heat from the outer diameter side thereof.

  Since the exhaust gas purification device 10f is configured as described above, exhaust gas containing fuel added from the fuel addition nozzle 11 flows through the outer diameter side exhaust circulation path 22, and fuel addition occurs in the inner diameter side exhaust circulation path 21. From the nozzle 11, no fuel is added and exhaust without fuel flows.

  And since the downstream side of the filter 19 is connected to the outside through the exhaust passage 4 in the outer diameter side exhaust circulation path 22, the exhaust gas containing fuel raises the temperature of the oxidation catalyst 18 and performs PM oxidation removal processing by the filter 19. And released into the atmosphere.

  On the other hand, since the downstream side of the filter 19 is connected to the low pressure EGR passage 31 in the inner diameter side exhaust circulation path 21, the exhaust gas that does not contain fuel flowing through the inner diameter side exhaust circulation path 21 passes through the low pressure EGR passage 31. To reflux. During this recirculation, the fuel does not enter the intake passage 3 because no fuel is contained in the exhaust gas. Therefore, it is difficult for the fuel to be mixed into the intake air supplied to the internal combustion engine 1 and the intake oxygen concentration or HC concentration of the intake air is difficult to change. Therefore, even if this intake air is taken in, the internal combustion engine 1 can suppress torque fluctuation.

  Further, although the exhaust gas flowing through the inner diameter side exhaust circulation path 21 contains NOx, since this exhaust gas is recirculated to the intake passage 3, NOx is not released to the atmosphere.

<Example 8>
Next, an exhaust emission control device 10g according to Embodiment 8 will be described with reference to FIG. In the present embodiment, the characteristic part of the present embodiment will be described, and the description of the items described in the above embodiment will be omitted.

  In the exhaust purification device 10g, cylindrical rectifying plates 20a and 20b are disposed across the oxidation catalyst 18 and the filter 19. A cylindrical rectifying plate 20 c is also disposed between the oxidation catalyst 18 and the filter 19. The rectifying plates 20a, 20b, and 20c form an inner diameter side exhaust circulation path 21 and an outer diameter side exhaust circulation path 22 in the exhaust purification apparatus 10g. Each of the rectifying plates 20a, 20b, 20c prevents the exhaust from entering and mixing between the inner diameter side exhaust circulation path 21 and the outer diameter side exhaust circulation path 22, and the exhaust flows through each of the exhaust circulation paths 21, 22. I am doing so.

  In the present embodiment, since the rectifying plate 20c is also disposed between the oxidation catalyst 18 and the filter 19, it is assumed that exhaust gas enters and mixes between the inner diameter side exhaust circulation path 21 and the outer diameter side exhaust circulation path 22. More can be prevented.

<Example 9>
Next, an exhaust purification device 10h according to Embodiment 9 will be described with reference to FIG. In the present embodiment, the characteristic part of the present embodiment will be described, and the description of the items described in the above embodiment will be omitted.

  In the exhaust gas purification apparatus 10h, in order to swirl the exhaust gas flowing through the outer-diameter side exhaust circulation path 22, an air guide plate 24a formed on the inner periphery of the outer wall 17 and an air guide formed on the outer periphery of the rectifying plate 20a. The board 24b and the air guide plate 24c formed in the outer periphery of the baffle plate 20c are provided. The air guide plates 24a, 24b, and 24c are plates that extend perpendicularly to the exhaust flow and vortex along the circumference of the exhaust purification device 10h.

The air guide plates 24a, 24b, and 24c correspond to the air guide means of the present invention. Further, as the air guide means, irregularities may be directly formed on the inner periphery of the outer wall 17 and the outer surfaces of the rectifying plates 20a and 20c, and at least one of the inner periphery of the outer wall 17 and the outer periphery of the rectifying plates 20a and 20c. Alternatively, the air guide means may be formed.

  In the present embodiment, the exhaust air flowing through the outer-diameter side exhaust circulation path 22 is swung as shown in the figure by the air guide plates 24a, 24b, and 24c, and the exhaust including fuel is supplied to the entire outer-diameter side of the rectifying plates 20a and 20c. Can supply.

<Example 10>
Next, an exhaust emission control device 10i according to Embodiment 10 will be described with reference to FIG. In the present embodiment, the characteristic part of the present embodiment will be described, and the description of the items described in the above embodiment will be omitted.

  In the exhaust purification device 10 i, a NOx catalyst 19 c is carried on a portion through which the exhaust gas flowing through the outer diameter side exhaust circulation path 22 of the filter 19 passes, that is, on the outer diameter side of the filter 19. The NOx catalyst 19c is the same as the NOx catalyst 19a of the above embodiment.

  For this reason, on the outer diameter side of the filter 19, as a process for recovering the performance of the filter 19, in addition to the PM oxidation removal process, a NOx reduction process and a SOx poisoning recovery process can be executed.

  In the present embodiment, since the NOx catalyst 19a is supported only on the outer diameter side of the filter 19, the NOx catalyst is not supported on the part where the exhaust gas in the inner diameter side exhaust circulation path 21 circulates, that is, the inner diameter side of the filter 19. The amount of catalyst supported can be reduced.

<Example 11>
Next, an exhaust emission control device 10j according to Example 11 will be described with reference to FIG. In the present embodiment, the characteristic part of the present embodiment will be described, and the description of the items described in the above embodiment will be omitted.

  In the exhaust gas purification apparatus 10j, the part through which the exhaust gas flowing through the inner diameter side exhaust flow path 21 of the filter 19 passes, that is, the pore diameter on the inner diameter side 19d of the filter 19 is made smaller than the pore diameter on the outer diameter side of the filter 19. ing.

  In the present embodiment, the PM trapping rate on the inner diameter side 19d of the filter 19 can be increased, and the bed temperature on the inner diameter side 19d of the filter 19 is unlikely to be lowered. it can.

<Example 12>
Next, an exhaust emission control device 10k according to Embodiment 12 will be described with reference to FIG. In the present embodiment, the characteristic part of the present embodiment will be described, and the description of the items described in the above embodiment will be omitted.

  A discharge hole 23 for discharging condensed water is provided in the rectifying plate 20b on the downstream side of the filter 19 in the exhaust purification device 10k.

  In the present embodiment, the condensed water accumulated in the inner diameter side exhaust circulation path 21 can be discharged from the discharge hole 23 to the outer diameter side exhaust circulation path 22 and further discharged from there. Thereby, it can suppress that condensed water flows into the intake passage 3 through the low pressure EGR passage 31 from the inner diameter side exhaust circulation passage 21.

<Example 13>
Next, an exhaust emission control device 101 according to Embodiment 13 will be described with reference to FIG. In the present embodiment, the characteristic part of the present embodiment will be described, and the description of the items described in the above embodiment will be omitted.

  The fuel addition nozzle 11 of this embodiment adds fuel toward the outer peripheral surface of the rectifying plate 20a on the upstream side of the oxidation catalyst 18.

  In this embodiment, the fuel added to the exhaust collides with the outer peripheral surface of the rectifying plate 20a, flows into the oxidation catalyst 18 while moving along the outer periphery of the rectifying plate 20a as shown by the arrows in the drawing, It can be distributed widely on the outer diameter side.

<Example 14>
Next, an exhaust purification system for an internal combustion engine according to Embodiment 14 will be described with reference to FIG. In the present embodiment, the characteristic part of the present embodiment will be described, and the description of the items described in the above embodiment will be omitted.

  In the present embodiment, a bypass passage 25 that connects the low-pressure EGR passage 31 and the exhaust passage 4 downstream of the exhaust throttle valve 12 is provided. The bypass passage 25 extends from a portion where the low pressure EGR cooler 33 is disposed in the low pressure EGR passage 31. For this reason, the exhaust gas flowing from the low pressure EGR passage 31 to the bypass passage 25 is also cooled by the low pressure EGR cooler 33.

  The bypass passage 25 is provided with an opening / closing valve 26 for adjusting the flow rate of the exhaust gas flowing through the bypass passage 25. The on-off valve 26 is connected to the ECU 13 via electric wiring, and the on-off valve 26 is controlled by the ECU 13.

  In this embodiment, the exhaust purification device 10b of the third embodiment is used as the exhaust purification device disposed in the exhaust passage 4. The exhaust purification device 10b carries a NOx catalyst 19a on a portion of the exhaust purification device 10b through which exhaust gas flowing through the inner diameter side exhaust circulation path 21 of the filter 19 passes, that is, on the inner diameter side of the filter 19.

  By the way, when fuel is added to the inner diameter side exhaust circulation passage 21 of the exhaust purification device 10b by the fuel addition nozzle 11, when the flow rate of the exhaust gas flowing through the exhaust passage 4 is high, the fuel is carried on the exhaust gas, It could not stay on the filter 19 and hardly acted on the NOx catalyst 19a. For this reason, a large amount of fuel must be added, leading to deterioration of fuel consumption.

  Therefore, when fuel is added to the inner diameter side exhaust circulation path 21 of the exhaust purification device 10b by the fuel addition nozzle 11, the exhaust throttle valve 12 is controlled to the closed side, and the on-off valve 26 is controlled to be in the open state, Exhaust gas is allowed to flow out from the outer diameter side exhaust circulation path 22 through the low pressure EGR passage 31 and the bypass passage 25 to the exhaust passage 4.

  According to this, when fuel is added to the inner diameter side exhaust circulation path 21 of the exhaust purification device 10b by the fuel addition nozzle 11, the exhaust throttle valve 12 is controlled to the closed side, so that the exhaust gas is discharged to the inner diameter side exhaust circulation path 21. Can be confined. For this reason, even when the flow rate of the exhaust gas flowing through the exhaust passage 4 is high, by adding the fuel by the fuel addition nozzle 11, the fuel stays in the filter 19 and acts on the NOx catalyst 19a, and the inner diameter side exhaust gas flow In the path 21, the air-fuel ratio can be suitably rich, or the temperature can be suitably raised to a predetermined temperature. Therefore, the process of restoring the performance of the filter 19 that requires the addition of fuel by the fuel addition nozzle 11, for example, the PM oxidation removal process, the NOx reduction process, and the SOx poisoning recovery process are suitably performed with less fuel consumption. it can. Thereby, fuel consumption deterioration can be kept to a minimum.

  Further, when the exhaust throttle valve 12 is controlled to the closed side, the flow of the exhaust gas is retarded, and the exhaust resistance increases, leading to a decrease in engine output. However, in this embodiment, when the exhaust throttle valve 12 is controlled to the closed side, the on-off valve 26 is controlled to be opened, and the exhaust gas is passed from the outer diameter side exhaust circulation path 22 to the low pressure EGR passage 31 and the bypass passage 25. Let it pass through and flow out to the exhaust passage 4. As a result, it is possible to suppress a decrease in engine output by suppressing an increase in exhaust resistance without delaying an exhaust flow.

  Here, when the fuel addition to the inner diameter side exhaust flow path 21 of the exhaust purification device 10b by the fuel addition nozzle 11 is completed and the exhaust throttle valve 12 is controlled to open, the fuel is added and passes through the exhaust throttle valve 12. The exhausted gas flows into the bypass passage 25 and may enter the intake passage 3 through the bypass passage 25 and the low pressure EGR passage 31. However, in this embodiment, when the fuel addition to the inner diameter side exhaust circulation path 21 of the exhaust purification device 10b by the fuel addition nozzle 11 is completed and the exhaust throttle valve 12 is controlled to open, the on-off valve 26 is closed. Let me speak. Thereby, it is possible to prevent the exhaust gas added with fuel and passing through the exhaust throttle valve 12 from flowing into the bypass passage 25. Therefore, the exhaust gas added with fuel and passed through the exhaust throttle valve 12 does not enter the intake passage 3 via the bypass passage 25 and the low pressure EGR passage 31.

  Here, a control routine when the internal combustion engine 1 of the present embodiment performs fuel addition from the fuel addition nozzle 11 will be described based on a flowchart shown in FIG. This routine is stored in advance in the ECU 13 and is a routine that is periodically executed.

  In step S101, the ECU 13 first determines whether or not fuel addition from the fuel addition nozzle 11 is being performed. If the process for restoring the performance of the filter 19, for example, the PM oxidation removal process, the NOx reduction process, or the SOx poisoning recovery process is being performed, it is determined that fuel addition is being performed.

  If an affirmative determination is made in step S101, the process proceeds to step S102. On the other hand, if a negative determination is made, this control routine is temporarily terminated.

  In step S102, the ECU 13 controls the exhaust throttle valve 12 to the closed side, controls the on-off valve 26 to the open state, and controls the low-pressure EGR valve 32 to the closed side.

  By controlling the exhaust throttle valve 12 to the closed side, the exhaust is confined in the inner diameter side exhaust circulation path 21. Further, by controlling the on-off valve 26 to the open state, the exhaust gas is allowed to flow from the outer diameter side exhaust circulation path 22 through the low pressure EGR passage 31 and the bypass passage 25 to the exhaust passage 4. Further, by controlling the low pressure EGR valve 32 to the closed side, the EGR operation using the low pressure EGR passage 31 is adjusted so that the internal combustion engine 1 can supply the low pressure EGR gas amount required by the operating state. The low-pressure EGR valve 32 is controlled to the closed side because the exhaust gas flowing out to the exhaust passage 4 passes through the low-pressure EGR passage 31 and the bypass passage 25. Therefore, the low-pressure EGR valve 32 flows into the intake passage 3 unless the low-pressure EGR valve 32 is controlled to the closed side. This is because the amount of low-pressure EGR gas to be increased increases.

  In step S103, the ECU 13 determines whether or not the fuel addition from the fuel addition nozzle 11 is completed. Specifically, it is determined that the fuel addition is completed when the process of restoring the performance of the filter 19, for example, the PM oxidation removal process, the NOx reduction process, and the SOx poisoning recovery process is completed.

  If an affirmative determination is made in step S103, the process proceeds to step S104. On the other hand, if a negative determination is made, the process returns to step S102 to form a loop.

  In step S104, the exhaust throttle valve 12 is controlled to the open side, the open / close valve 26 is controlled to be closed, and the low pressure EGR valve 32 is controlled to open to the normal opening.

  By controlling the exhaust throttle valve 12 to the open side, the exhaust confined in the inner diameter side exhaust circulation path 21 flows out to the downstream exhaust path 4. Further, the exhaust gas is prevented from flowing through the bypass passage 25 by controlling the on-off valve 26 to the closed state. Further, by controlling the low pressure EGR valve 32 to open to the normal opening, the low pressure EGR gas amount required by the internal combustion engine 1 depending on the operating state is supplied in the EGR operation using the low pressure EGR passage 31. Thereafter, this control routine is temporarily terminated.

  By executing this control routine, the fuel addition from the fuel addition nozzle 11 can be suitably performed with a small amount of fuel consumption. Thereby, fuel consumption deterioration can be kept to a minimum.

<Example 15>
Next, an exhaust purification system for an internal combustion engine according to Embodiment 15 will be described with reference to FIG. In the present embodiment, the characteristic part of the present embodiment will be described, and the description of the items described in the above embodiment will be omitted.

  In the present embodiment, as in the fourteenth embodiment, a bypass passage 25 that connects the low-pressure EGR passage 31 and the exhaust passage 4 downstream of the exhaust throttle valve 12 is provided. The bypass passage 25 extends from a portion where the low pressure EGR cooler 33 is disposed in the low pressure EGR passage 31.

  Further, unlike the fourteenth embodiment, the bypass passage 25 is not provided with an opening / closing valve for adjusting the flow rate of the exhaust gas flowing through the bypass passage 25.

  In this embodiment, the exhaust purification device 10b of the third embodiment is used as the exhaust purification device disposed in the exhaust passage 4. The exhaust purification device 10b carries a NOx catalyst 19a on a portion of the exhaust purification device 10b through which exhaust gas flowing through the inner diameter side exhaust circulation path 21 of the filter 19 passes, that is, on the inner diameter side of the filter 19.

  By the way, when fuel is added to the inner diameter side exhaust circulation passage 21 of the exhaust purification device 10b by the fuel addition nozzle 11, when the flow rate of the exhaust gas flowing through the exhaust passage 4 is high, the fuel is carried on the exhaust gas, It could not stay on the filter 19 and hardly acted on the NOx catalyst 19a. For this reason, a large amount of fuel must be added, leading to deterioration of fuel consumption.

  Therefore, when fuel is added to the inner diameter side exhaust flow path 21 of the exhaust gas purification device 10b by the fuel addition nozzle 11 for SOx poisoning recovery processing, the exhaust throttle valve 12 is controlled to the closed side, and the exhaust is discharged to the outer diameter. The low-pressure EGR passage 31 and the bypass passage 25 are allowed to pass from the side exhaust circulation passage 22 to the exhaust passage 4.

  According to this, when fuel is added to the inner diameter side exhaust circulation path 21 of the exhaust purification device 10b by the fuel addition nozzle 11 for SOx poisoning recovery processing, the inner diameter is controlled by controlling the exhaust throttle valve 12 to the closed side. The exhaust can be confined in the side exhaust circulation path 21. For this reason, even when the flow rate of the exhaust gas flowing through the exhaust passage 4 is high, by adding the fuel by the fuel addition nozzle 11, the fuel stays in the filter 19 and acts on the NOx catalyst 19a, and the inner diameter side exhaust gas flow In the path 21, the air-fuel ratio can be suitably rich, or the temperature can be suitably raised to a predetermined temperature. Therefore, the SOx poisoning recovery process that requires the fuel to be added by the fuel addition nozzle 11 can be suitably implemented with a small amount of fuel consumption. Thereby, fuel consumption deterioration can be kept to a minimum.

  In this embodiment, the case where fuel is added by the fuel addition nozzle 11 for the SOx poisoning recovery process is described. However, the effect of reducing the fuel consumption described above restores the performance of the filter 19. Even when the fuel is added by the fuel addition nozzle 11 for processing, for example, PM oxidation removal processing or NOx reduction processing, it can be exhibited.

  Further, when the exhaust throttle valve 12 is controlled to the closed side, the flow of the exhaust gas is retarded, and the exhaust resistance increases, leading to a decrease in engine output. However, in this embodiment, when the exhaust throttle valve 12 is controlled to the closed side, the exhaust gas flows out from the outer diameter side exhaust circulation path 22 through the low pressure EGR passage 31 and the bypass passage 25 to the exhaust passage 4. As a result, it is possible to suppress a decrease in engine output by suppressing an increase in exhaust resistance without delaying an exhaust flow.

  Here, when the fuel addition to the inner diameter side exhaust flow path 21 of the exhaust gas purification apparatus 10b by the fuel addition nozzle 11 for SOx poisoning recovery processing is completed and the exhaust throttle valve 12 is controlled to the open side, SOx There is a risk that the exhaust gas including the gas flows into the bypass passage 25 from the exhaust passage 4 and flows into the intake passage 3 through the bypass passage 25 and the low-pressure EGR passage 31.

  Therefore, in the present embodiment, when the fuel addition by the fuel addition nozzle 11 for the SOx poisoning recovery process is completed and the exhaust throttle valve 12 is controlled to the open side, the exhaust passage downstream from the inner diameter side exhaust circulation passage 21. While the SOx is discharged to 4, the low pressure EGR valve 32 is closed. As a result, the exhaust gas containing SOx can be prevented from flowing into the intake passage 3 from the low pressure EGR passage 31. Therefore, the exhaust gas including SOx does not enter the intake passage 3 via the bypass passage 25 and the low pressure EGR passage 31.

  Further, when the low pressure EGR valve 32 is closed as described above, the low pressure EGR gas is not supplied, so that the amount of EGR gas to be supplied to the internal combustion engine 1 is insufficient.

  Therefore, in this embodiment, when the low pressure EGR valve 32 is closed as described above, the amount of the high pressure EGR gas in the EGR operation using the high pressure EGR passage 41 is increased and before flowing into the exhaust purification device 10b. The amount of EGR gas to be supplied to the internal combustion engine 1 is compensated by returning the exhaust gas to the intake passage 3 of the internal combustion engine. As a method of returning the exhaust gas before flowing into the exhaust purification device 10b to the intake passage 3 of the internal combustion engine 1, in addition to the EGR operation using the high pressure EGR passage 41, the intake valve and the exhaust valve of the internal combustion engine 1 are simultaneously used. An internal EGR operation may be used in which exhaust flows backward in the internal combustion engine 1 by an open valve overlap.

  Here, a control routine when the internal combustion engine 1 of the present embodiment performs fuel addition from the fuel addition nozzle 11 for SOx poisoning recovery processing will be described based on the flowchart shown in FIG. This routine is stored in advance in the ECU 13 and is a routine that is periodically executed.

  In step S201, the ECU 13 first determines whether or not fuel addition from the fuel addition nozzle 11 is being performed for the SOx poisoning recovery process. That is, it is determined whether the SOx poisoning recovery process is being performed.

  If an affirmative determination is made in step S201, the process proceeds to step S202. On the other hand, if a negative determination is made, this control routine is temporarily terminated.

  In step S202, the ECU 13 controls the exhaust throttle valve 12 to the closed side and controls the low pressure EGR valve 32 to the closed side.

  By controlling the exhaust throttle valve 12 to the closed side, the exhaust is confined in the inner diameter side exhaust circulation path 21. At this time, the exhaust gas passes through the low-pressure EGR passage 31 and the bypass passage 25 from the outer diameter side exhaust circulation passage 22 and flows out to the exhaust passage 4. Further, by controlling the low pressure EGR valve 32 to the closed side, the EGR operation using the low pressure EGR passage 31 is adjusted so that the internal combustion engine 1 can supply the low pressure EGR gas amount required by the operating state. The low-pressure EGR valve 32 is controlled to the closed side because the exhaust gas flowing out to the exhaust passage 4 passes through the low-pressure EGR passage 31 and the bypass passage 25. Therefore, the low-pressure EGR valve 32 flows into the intake passage 3 unless the low-pressure EGR valve 32 is controlled to the closed side. This is because the amount of low-pressure EGR gas to be increased increases.

  In step S203, the ECU 13 determines whether or not the fuel addition from the fuel addition nozzle 11 is completed for the SOx poisoning recovery process. That is, it is determined whether or not the SOx poisoning recovery process is completed.

  If an affirmative determination is made in step S203, the process proceeds to step S204. On the other hand, if a negative determination is made, the process returns to step S202 to form a loop.

  In step S204, the ECU 13 controls the exhaust throttle valve 12 to the open side, controls the low pressure EGR valve 32 to the closed state, and controls the high pressure EGR valve 42 to the open side.

  By controlling the exhaust throttle valve 12 to the open side, the exhaust gas containing SOx confined in the inner diameter side exhaust circulation path 21 flows out to the downstream exhaust passage 4. Further, by controlling the low pressure EGR valve 32 to be in a closed state, the exhaust gas including SOx confined in the inner diameter side exhaust circulation path 21 is prevented from flowing into the intake path 3 via the low pressure EGR path 31. Furthermore, by controlling the high pressure EGR valve 42 to the open side, the amount of EGR gas required by the internal combustion engine 1 depending on the operating state is reduced by the amount of the EGR gas that the EGR operation using the low pressure EGR passage 31 is stopped. Compensate by increasing the amount.

  In step S <b> 205, the ECU 13 determines whether or not the exhaust gas including SOx confined in the inner diameter side exhaust circulation path 21 is exhausted from the inner diameter side exhaust circulation path 21. For example, when a predetermined time has elapsed since the exhaust throttle valve 12 was controlled to open, it is determined that the exhaust gas containing SOx confined in the inner diameter side exhaust circulation path 21 has been exhausted from the inner diameter side exhaust circulation path 21. Here, the predetermined time is a time to the extent that exhaust containing SOx confined in the inner diameter side exhaust circulation path 21 is discharged from the inner diameter side exhaust circulation path 21.

  If an affirmative determination is made in step S205, the process proceeds to step S206. On the other hand, if a negative determination is made, the process returns to step S204 to form a loop.

  In step S206, the ECU 13 controls the low pressure EGR valve 32 to the opening side to the normal opening, and controls the high pressure EGR valve 42 to the closing side to the normal opening.

  By controlling the low pressure EGR valve 32 to open to the normal opening, the low pressure EGR gas amount required by the internal combustion engine 1 depending on the operating state is supplied in the EGR operation using the low pressure EGR passage 31. Further, by controlling the high-pressure EGR valve 42 to the normal opening degree so as to be closed, the high-pressure EGR gas amount required by the internal combustion engine 1 depending on the operating state is supplied in the EGR operation using the high-pressure EGR passage 41. Thereafter, this control routine is temporarily terminated.

  By executing this control routine, the fuel addition from the fuel addition nozzle 11 can be suitably performed for the SOx poisoning recovery process with less fuel consumption. Thereby, fuel consumption deterioration can be kept to a minimum. Further, it is possible to prevent the SOx contained in the exhaust from flowing into the intake passage 3 after the SOx poisoning recovery process.

  The exhaust gas purification system for an internal combustion engine according to the present invention is not limited to the above-described embodiments, and various modifications may be made without departing from the gist of the present invention.

1 is a diagram illustrating an internal combustion engine and an intake / exhaust system thereof according to Embodiment 1. FIG. 1 is a diagram illustrating an exhaust emission control device according to a first embodiment. It is a figure which shows the exhaust gas purification apparatus which concerns on Example 2. FIG. FIG. 6 is a diagram illustrating an exhaust emission control device according to a third embodiment. It is a figure which shows the exhaust gas purification apparatus which concerns on Example 4. FIG. FIG. 10 is a diagram illustrating an exhaust emission control device according to a fifth embodiment. FIG. 10 is a diagram illustrating an exhaust emission control device according to a sixth embodiment. FIG. 10 is a diagram showing an exhaust emission control device according to a seventh embodiment. FIG. 10 is a diagram illustrating an exhaust emission control device according to an eighth embodiment. FIG. 10 is a diagram illustrating an exhaust emission control device according to a ninth embodiment. It is a figure which shows the exhaust gas purification apparatus which concerns on Example 10. FIG. FIG. 12 is a diagram showing an exhaust purification device according to an eleventh embodiment. FIG. 12 is a diagram showing an exhaust emission control apparatus according to a twelfth embodiment. FIG. 16 is a diagram showing an exhaust emission control device according to a thirteenth embodiment. FIG. 18 is a diagram showing an internal combustion engine and an intake / exhaust system thereof according to Embodiment 14; It is a flowchart which shows the control routine at the time of implementing the fuel addition which concerns on Example 14. FIG. FIG. 17 is a diagram showing an internal combustion engine according to a fifteenth embodiment and its intake / exhaust system. FIG. 25 is a flowchart showing a control routine for performing fuel addition for SOx poisoning recovery processing according to Embodiment 15. FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Internal combustion engine 2 Cylinder 3 Intake passage 4 Exhaust passage 5 Turbocharger 5a Compressor housing 5b Turbine housing 6 Throttle valve 7 Air flow meter 8 Intercooler 9 Throttle valve 10-10l Exhaust purification device 11 Fuel addition nozzle 12 Exhaust throttle valve 13 ECU
14 Accelerator pedal 15 Accelerator opening sensor 16 Crank position sensor 17 Outer wall 17a Wall surface 18 Oxidation catalyst 19 Filter 19a, 19c NOx catalyst 19b, 10d Inner diameter side 20a, 20b, 20c of filter Current plate 21 Outer diameter side exhaust flow path 22 Outer diameter side Exhaust flow path 23 Discharge holes 24a, 24b, 24c Air guide plate 25 Bypass passage 26 On-off valve 30 Low pressure EGR device 31 Low pressure EGR passage 32 Low pressure EGR cooler 33 Low pressure EGR cooler 40 High pressure EGR device 41 High pressure EGR passage 42 High pressure EGR valve

Claims (16)

Exhaust purification means disposed in the exhaust passage of the internal combustion engine;
A plurality of exhaust flow passages formed in an exhaust passage straddling the exhaust purification means in the exhaust flow direction;
Fuel addition means for adding fuel to the exhaust on the upstream side of the exhaust purification means, the exhaust flowing through one of the plurality of exhaust circulation paths;
An EGR passage that recirculates the exhaust flowing through the other of the plurality of exhaust flow passages from the downstream side of the exhaust purification means to the intake passage of the internal combustion engine;
An exhaust gas purification system for an internal combustion engine, comprising:   2. The exhaust gas purification system for an internal combustion engine according to claim 1, further comprising a rectifying plate that partitions one of the plurality of exhaust flow paths from the other.   3. The exhaust of an internal combustion engine according to claim 2, wherein the rectifying plate has a cylindrical shape and partitions one and the other of the plurality of exhaust flow paths into an inner diameter side and an outer diameter side of the rectifying plate. Purification system.   4. The internal combustion engine according to claim 3, wherein one of the plurality of exhaust circulation paths is an inner diameter side of the rectifying plate, and the other of the plurality of exhaust circulation paths is an outer diameter side of the rectifying plate. Engine exhaust purification system.   A wall surface disposed at the center of the fuel addition means and facing the inlet of one of the plurality of exhaust flow paths on the inner diameter side of the rectifying plate, a convex portion whose center protrudes downstream in the exhaust flow direction. The exhaust gas purification system for an internal combustion engine according to claim 4, wherein the exhaust gas purification system is provided in a shape.   4. The internal combustion engine according to claim 3, wherein one of the plurality of exhaust circulation paths is an outer diameter side of the rectifying plate, and the other of the plurality of exhaust circulation paths is an inner diameter side of the rectifying plate. Engine exhaust purification system.   The exhaust gas purification system for an internal combustion engine according to claim 6, further comprising an air guide means for turning the exhaust gas flowing through one of the plurality of exhaust gas flow paths on the outer diameter side of the rectifying plate.   The exhaust purification system for an internal combustion engine according to claim 6, wherein the fuel adding means adds fuel toward an outer peripheral surface of the rectifying plate upstream of the exhaust purification means.   9. The exhaust gas purification device according to claim 1, wherein the exhaust gas purification device includes two upstream exhaust gas purification devices and two downstream exhaust gas purification devices arranged in series in an exhaust gas flow direction. 10. An exhaust purification system for an internal combustion engine as described.   10. The exhaust gas purification system for an internal combustion engine according to claim 9, wherein the rectifying plate is also provided between the upstream side exhaust purification unit and the downstream side exhaust purification unit.   The internal combustion engine according to any one of claims 1 to 10, wherein an NOx storage reduction catalyst is supported on a portion of the exhaust gas purification unit in which one exhaust gas flows. Exhaust purification system.   4. The pore diameter of a portion of the exhaust gas purification unit where the exhaust gas on the inner diameter side of the rectifying plate circulates is made smaller than the pore diameter of a portion where the exhaust gas on the outer diameter side of the rectifying plate circulates. The exhaust gas purification system for an internal combustion engine according to any one of to 11.   The exhaust purification system for an internal combustion engine according to any one of claims 3 to 12, wherein a discharge hole for discharging condensed water is provided in the rectifying plate on the downstream side of the exhaust purification means. An exhaust throttle valve that is disposed in the exhaust passage downstream of the exhaust purification means and adjusts the flow rate of exhaust gas that flows through one of the plurality of exhaust circulation paths;
A bypass passage connecting between the EGR passage and the exhaust passage downstream of the exhaust throttle valve;
With
When adding fuel by the fuel adding means, the exhaust throttle valve is controlled to the closed side, and exhaust is passed from the other of the plurality of exhaust circulation paths to the exhaust path through the EGR passage and the bypass passage. The exhaust gas purification system for an internal combustion engine according to any one of claims 1 to 13, wherein the exhaust gas is discharged. An on-off valve for adjusting the flow rate of exhaust gas flowing through the bypass passage in the bypass passage;
15. The exhaust gas purification system for an internal combustion engine according to claim 14, wherein when the fuel is added by the fuel addition means and the exhaust throttle valve is controlled to be closed, the on-off valve is opened. An EGR valve for adjusting a flow rate of exhaust gas flowing through the EGR passage in the EGR passage;
When the fuel addition for the SOx poisoning recovery process by the fuel addition means is completed and the exhaust throttle valve is controlled to open, the sulfur component from one of the plurality of exhaust flow paths to the exhaust path downstream The exhaust gas purification of the internal combustion engine according to claim 14, wherein the EGR valve is closed while exhaust gas is being exhausted, and the exhaust gas before flowing into the exhaust gas purification means is recirculated to the intake passage of the internal combustion engine. system.

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