JP2018031301A - Exhaust emission control device for engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an exhaust emission control device for an engine, capable of simultaneously and appropriately performing regeneration processing for a NOx storage catalyst and regeneration processing for a particulate filter while stably supplying air into an exhaust passage on the upstream side of the particulate filter.SOLUTION: The exhaust emission control device includes an introduction passage 45 connected at one end side to a connection part 26a of an exhaust passage 26 at the downstream side of a NOx storage catalyst 38 and at the upstream side of a particulate filter 39, and opened at the other end side to outside air to introduce the outside air, an exhaust gas circulation passage 47 connecting the exhaust passage 26 at the downstream side of the particulate filter 39 and the introduction passage 45, a supply pump 46 provided in the introduction passage 45, and a first on-off valve 48 provided in the exhaust gas circulation passage 47 for opening/closing the exhaust gas circulation passage 47.SELECTED DRAWING: Figure 1

Description

  The present invention relates to an engine exhaust gas purification apparatus including a NOx storage catalyst and a particulate filter for purifying exhaust gas.

  The exhaust gas emitted from engines mounted on automobiles, etc. includes exhausts such as carbon monoxide (CO), hydrocarbons (HC), nitrogen oxides (NOx), and particulate matter (PM). Contains gas components. For this reason, a three-way catalyst for decomposing (reducing or the like) the substance and a particulate filter for capturing PM are provided in the exhaust passage of the engine.

  For example, in the case of an engine that burns in an oxidizing atmosphere by controlling the air / fuel ratio from the stoichiometric air / fuel ratio (stoichiometric) to a lean air / fuel ratio, such as a diesel engine, a three-way catalyst uses nitrogen oxides in the exhaust gas. (NOx) cannot be sufficiently purified. For this reason, some exhaust passages of this type of engine are provided with a NOx storage catalyst. The NOx storage catalyst stores NOx in the exhaust if the air-fuel ratio of the exhaust is lean, and releases and reduces the stored NOx if the air-fuel ratio of the exhaust is rich.

  In a diesel engine or the like, normally, since the air-fuel ratio of exhaust gas is lean, nitrogen oxides are stored in the NOx storage catalyst. For this reason, it is necessary to perform a regeneration process (NOx purge) for decomposing (reducing) NOx stored in the NOx storage catalyst by enriching the air-fuel ratio of the exhaust at a predetermined timing.

  Further, since the sulfur component is contained as a harmful component in the fuel, the sulfur component reacts with oxygen to become sulfur oxide (SOx) and is stored in the NOx storage catalyst instead of NOx (S poisoning). . For this reason, it is necessary to perform a regeneration process (sulfur purge: S purge) for removing sulfur oxide (SOx) at a predetermined timing. In order to perform this regeneration process (S purge), it is necessary to enrich the air-fuel ratio and raise the NOx storage catalyst to a high temperature equal to or higher than a predetermined temperature.

  In addition, particulate filters accumulate in the interior with use and increase the passage resistance. For this reason, it is necessary to perform the regeneration process for the particulate filter at a predetermined timing. That is, it is necessary to raise the temperature of the particulate filter and burn and remove the PM accumulated inside.

  Here, the regeneration process of the NOx storage catalyst (NOx purge and S purge) requires that the inside of the catalyst be in an oxygen-deficient state. On the other hand, the regeneration process of the particulate filter requires that the inside of the filter is sufficiently supplied with oxygen. For this reason, in the present engine, the regeneration process of the NOx storage catalyst and the regeneration process of the particulate filter are generally performed separately, and a large amount of fuel is consumed in each regeneration process. .

  In order to solve such problems, a NOx trap catalyst (NOx storage catalyst) provided in the exhaust passage, a PM trap (particulate filter) provided downstream of the NOx trap catalyst, and an upstream side of the PM trap An air supply device capable of supplying air to the exhaust passage, and regenerating the NOx trap catalyst (catalyst regeneration) by introducing air to the PM filter from a path different from the path passing through the NOx trap catalyst In addition, a technique for simultaneously performing PM filter regeneration (filter regeneration) has been proposed (see, for example, Patent Document 1).

  Specifically, this Patent Document 1 has, as an air supply device, an air introduction path that connects an intake passage downstream of a compressor of a supercharger and an upstream exhaust passage of a PM trap. The structure which introduce | transduces air into PM filter via is disclosed.

Japanese Patent Laid-Open No. 2003-201828

  However, with the configuration described in Patent Document 1, there is a possibility that air cannot be stably supplied to the particulate filter (PM filter).

  For example, since the pressure of the exhaust gas flowing through the exhaust passage is usually higher than the atmospheric pressure, it is necessary to increase the pressure in order to introduce air into the exhaust passage. In the configuration described in Patent Document 1, one end side of the air introduction path is connected to an intake passage downstream of the compressor that can be a negative pressure depending on the operating state of the engine. For this reason, depending on the operating state of the engine, the air in the air introduction path may have a negative pressure, and the air may flow backward from the upstream exhaust passage to the intake passage through the air introduction path.

  In addition, when a large amount of PM (soot) is accumulated on the particulate filter, when air is supplied to the particulate filter, the temperature of the particulate filter may rise excessively, leading to deterioration or damage of the particulate filter. is there. For this reason, it is desirable that the amount of air (oxygen) supplied to the particulate filter can be adjusted as appropriate.

  The present invention has been made in view of such circumstances, and stably supplies air to the exhaust passage on the upstream side of the particulate filter to regenerate the NOx storage catalyst and regenerate the particulate filter. It is an object of the present invention to provide an engine exhaust gas purification device capable of appropriately performing the above and the like simultaneously.

  It is another object of the present invention to provide an engine exhaust purification device that can appropriately adjust the amount of air supplied to the particulate filter during the regeneration process of the particulate filter.

  An aspect of the present invention that solves the above problem is an engine exhaust purification device that includes a NOx storage catalyst provided in an exhaust passage of an engine and a particulate filter provided downstream of the NOx storage catalyst in the exhaust passage. And an exhaust passage in which one end side is connected to a connection portion downstream of the NOx storage catalyst in the exhaust passage and upstream of the particulate filter, and the other end side is opened to the outside air and the outside air is introduced. An exhaust circulation passage connecting the downstream side of the particulate filter and the introduction passage, a supply pump provided in the introduction passage, and a first on-off valve provided in the exhaust circulation passage for opening and closing the exhaust circulation passage. The engine exhaust gas purification apparatus is characterized by the above.

  Here, the engine exhaust purification device performs the regeneration process of the particulate filter at the timing when the regeneration process of the NOx storage catalyst is performed by the catalyst regeneration process unit that performs the regeneration process of the NOx storage catalyst and the regeneration process of the NOx storage catalyst. A filter regeneration processing unit that performs the operation of the supply pump at a timing when the temperature of the NOx storage catalyst rises to the first temperature or higher, and passes the gas including the outside air through the introduction passage. It is preferable to supply to the connection part of the exhaust passage.

  The filter regeneration processing unit opens the first on-off valve when the temperature of the particulate filter becomes equal to or higher than a second temperature higher than the first temperature, and includes exhaust gas supplied from the exhaust circulation passage together with outside air. It is preferable to supply gas to the connection part of the exhaust passage through the introduction passage.

  The engine exhaust purification device further includes a second on-off valve provided in the introduction passage to open and close the introduction passage, and the filter regeneration processing unit includes a third temperature at which the temperature of the particulate filter is higher than the second temperature. When the temperature is higher than the temperature, it is preferable to close the second on-off valve and supply the gas composed of the exhaust gas supplied from the exhaust circulation passage to the connection portion of the exhaust passage through the introduction passage.

  The filter regeneration processing unit may close the first on-off valve when the temperature of the particulate filter is higher than the first temperature and lower than a fourth temperature that is lower than or equal to the second temperature. In this case, it is preferable to gradually close the first on-off valve.

  According to such an exhaust emission control device for an engine of the present invention, gas containing air can be stably supplied to the exhaust passage on the upstream side of the particulate filter. For this reason, the regeneration process of the particulate filter can be appropriately performed while the regeneration process (S purge) of the NOx storage catalyst is being performed.

  Also, the amount of air introduced into the particulate filter is appropriately adjusted during the regeneration process of the particulate filter by appropriately controlling the first on-off valve and allowing the exhaust to flow into the introduction passage through the exhaust circulation passage. can do. That is, it is possible to appropriately reduce the oxygen concentration of the gas supplied to the exhaust passage on the upstream side of the particulate filter, and to effectively suppress the temperature rise (overheating) of the particulate filter.

1 is a schematic view showing an overall configuration of an engine including an exhaust purification device according to the present invention. It is a figure explaining the flow of the gas of an exhaust pipe, an introduction pipe, and an exhaust circulation pipe. It is a figure explaining the flow of the gas of an exhaust pipe, an introduction pipe, and an exhaust circulation pipe.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
As shown in FIG. 1, the engine 10 according to the present embodiment is an in-line four-cylinder diesel engine, and includes an engine body 11 in which four cylinders are formed. The engine body 11 includes a cylinder head 12 and a cylinder block 13, and a piston 14 is accommodated in the cylinder block 13. The piston 14 is connected to the crankshaft 16 via a connecting rod 15. The piston 14, the cylinder head 12 and the cylinder block 13 form a combustion chamber 17 for each cylinder.

  An intake port 18 that opens to the combustion chamber 17 of each cylinder is formed in the cylinder head 12, and an intake pipe (intake passage) 20 including an intake manifold 19 is connected to the intake port 18. The intake manifold 19 is provided with an intake pressure sensor (MAP sensor) 21 that detects intake pressure and an intake temperature sensor 22 that detects the temperature of intake air. An intake valve 23 is provided in each intake port 18, and each intake port 18 is opened and closed by the intake valve 23.

  The cylinder head 12 is formed with an exhaust port 24 that opens into the combustion chamber 17 of each cylinder, and an exhaust pipe (exhaust passage) 26 including an exhaust manifold 25 is connected to the exhaust port 24. An exhaust valve 27 is provided in the exhaust port 24, and the exhaust port 24 is opened and closed by the exhaust valve 27, similarly to the intake port 18. Since the intake valve 23 and the exhaust valve 27 have existing configurations, detailed description thereof is omitted, but the intake valve 23 and the exhaust valve 27 are opened and closed at a predetermined timing by a cam that rotates in conjunction with the reciprocating motion of the piston 14.

  Each cylinder is provided with an injector (fuel injection valve) 30 for injecting fuel. Although not shown, each injector 30 is connected to a common rail, and the comment rail is connected to a fuel tank via a supply pump (high pressure pump). Fuel is pumped from the fuel tank to the common rail by the supply pump, and high-pressure fuel in the common rail is injected from each injector 30.

  A turbocharger (supercharger) 32 is provided in the middle of the intake pipe 20 and the exhaust pipe 26. The turbocharger 32 includes a turbine 32a and a compressor 32b, and the turbine 32a and the compressor 32b are connected by a turbine shaft 32c. When the exhaust gas flows into the turbocharger 32, the turbine 32a is rotated by the flow of the exhaust gas, and the compressor 32b is rotated with the rotation of the turbine 32a. Air (intake air) pressurized by the rotation of the compressor 32b is sent to the intake pipe 20 and supplied to the combustion chamber 17 of each cylinder.

  An air cleaner 33 is provided in the intake pipe 20 on the upstream side of the compressor 32 b of the turbocharger 32. In addition, an intercooler 34 for cooling the intake air whose temperature has increased due to pressurization by the turbocharger 32 is disposed in the intake pipe 20 on the downstream side of the compressor 32 b of the turbocharger 32. The intake pipe 20 on the downstream side of the intercooler 34 is provided with a throttle valve 35 and a throttle position sensor (TPS) 36.

  On the other hand, the exhaust pipe 26 on the downstream side of the turbine 32a of the turbocharger 32 is provided with an exhaust purification catalyst and a diesel particulate filter constituting an exhaust purification device. In this embodiment, a NOx storage catalyst 38 that is an exhaust purification catalyst is provided on the upstream side, and a diesel particulate filter (hereinafter referred to as DPF) 39 is provided on the downstream side of the NOx storage catalyst 38. An air-fuel ratio sensor (air-fuel ratio detection means) 40 for detecting the air-fuel ratio of the exhaust gas flowing out from the NOx storage catalyst 38 is provided in the exhaust pipe 26 near the outlet of the NOx storage catalyst 38. Similarly, an air-fuel ratio sensor (air-fuel ratio detecting means) 41 for detecting the air-fuel ratio of the exhaust gas flowing out from the DPF 39 is also provided in the exhaust pipe 26 near the outlet of the DPF 39. These air-fuel ratio sensors 40 and 41 may detect oxygen concentration in the exhaust gas. Further, temperature sensors (temperature detection means) 42 and 43 for detecting the temperature of the exhaust are provided in the exhaust pipe 26 near the outlets of the NOx storage catalyst 38 and the DPF 39.

In the present embodiment, only the NOx storage catalyst is provided as the exhaust purification catalyst. However, the exhaust purification catalyst only needs to include the NOx storage catalyst. For example, the exhaust purification catalyst includes a diesel oxidation catalyst and the like together with the NOx storage catalyst. Also good. In the diesel oxidation catalyst, nitrogen monoxide (NO) in the exhaust is oxidized to generate nitrogen dioxide (NO ₂ ).

Here, the NOx occlusion catalyst 38, for example, supports a noble metal such as platinum (Pt) and palladium (Pd) on a honeycomb structure carrier made of a ceramic material, and as an occlusion agent such as barium (Ba). An alkali metal or an alkaline earth metal is supported. The NOx storage catalyst 38 temporarily stores nitrogen oxides (NOx) as exhaust components in an oxidizing atmosphere, and releases NOx in a reducing atmosphere containing, for example, carbon monoxide (CO) and hydrocarbons (HC). And reduced to nitrogen (N ₂ ) or the like. Since the engine 10 according to the present embodiment is a diesel engine, the NOx occlusion catalyst 38 normally only occludes NOx, and the occluded NOx is not decomposed (reduced).

  For this reason, every time the engine 10 is operated for a predetermined period, for example, a regeneration process (NOx purge) for removing the stored NOx is performed. In this regeneration process (NOx purge), fuel as a reducing agent is supplied to the NOx storage catalyst at a predetermined timing. As a result, the inside of the NOx storage catalyst 38 becomes a reducing atmosphere, and the stored NOx is decomposed (reduced) and removed from the NOx storage catalyst 38.

  Further, the NOx occlusion catalyst 38 occludes sulfur oxide (SOx), which is an exhaust component, in the same manner as nitrogen oxide (NOx). For this reason, regeneration processing (S purge) for removing SOx at a predetermined timing is also performed. In this regeneration process (S purge), fuel as a reducing agent is appropriately supplied to the exhaust to enrich the exhaust air-fuel ratio, and the NOx storage catalyst 38 is heated to a predetermined temperature (for example, about 700 ° C.) or higher. As a result, the stored sulfur oxide (SOx) is decomposed (reduced) and removed from the NOx storage catalyst 38.

For example, the DPF 39 is a filter having a honeycomb structure formed of a ceramic material. The PM trapped in the DPF 39 is oxidized (combusted) by NO ₂ in the exhaust gas and discharged as CO ₂ , and the NO ₂ remaining in the DPF 39 is decomposed into N ₂ and discharged. The DPF 39 is also subjected to regeneration processing (DPF regeneration) at a predetermined timing in order to remove PM accumulated inside. In this DPF regeneration, similarly to the S purge of the NOx occlusion catalyst 38, the DPF 39 is heated to a predetermined first temperature (for example, 600 ° C.) or more, thereby burning the PM accumulated in the DPF 39.

  By the way, in the regeneration process of the DPF 39, it is necessary to raise the DPF 39 to the first temperature or more like the S purge of the NOx storage catalyst 38 as described above. On the other hand, unlike the S purge, the exhaust air-fuel ratio of the DPF 39 is made lean. It is necessary to make it. Therefore, the S purge of the NOx storage catalyst 38 and the regeneration process of the DPF 39 have to be performed separately.

  However, the engine 10 according to the present embodiment includes an introduction pipe (introduction passage) 45, which will be described in detail below, as a part of the exhaust gas purification device. Air (oxygen) can be supplied to the exhaust pipe 26. That is, air (oxygen) can be introduced into the DPF 39 via the introduction pipe 45. Therefore, even when the exhaust air-fuel ratio of the NOx storage catalyst 38 is enriched, the exhaust air-fuel ratio in the DPF 39 can be made lean. Therefore, the regeneration process of the DPF 39 can be performed simultaneously while the S purge of the NOx storage catalyst 38 is being performed.

  One end of the introduction pipe 45 is connected to the connection portion 26a downstream of the NOx storage catalyst of the exhaust pipe and upstream of the DPF 39, and the other end is opened to the outside air (see FIG. 1). The introduction pipe 45 is provided with a supply pump 46 constituted by an electric pump or the like, and outside air flows into the introduction pipe 45 by operating the supply pump 46. A gas including the outside air that has flowed in (hereinafter referred to as introduction gas) is supplied to the connection portion 26a of the exhaust pipe 26 through the introduction pipe.

  Further, the introduction pipe 45 is connected to the exhaust pipe 26 via an exhaust circulation pipe (exhaust circulation passage) 47. The exhaust circulation pipe 47 connects the downstream side (open side) of the introduction pipe 45 with respect to the supply pump 46 and the downstream side of the DPF 39 of the exhaust pipe 26. The exhaust gas flowing out from the DPF 39 is supplied to the introduction pipe 45 via the exhaust circulation pipe 47.

  The exhaust circulation pipe 47 is provided with a first on-off valve 48 for adjusting the amount of exhaust flowing into the exhaust circulation pipe 47. Although the arrangement of the first on-off valve 48 is not particularly limited, in the present embodiment, the first on-off valve 48 is provided in the vicinity of the connection portion of the exhaust circulation pipe 47 with the exhaust pipe 26. The introduction pipe 45 is provided with a second on-off valve 49 that adjusts the amount of outside air flowing into the introduction pipe 45. The second opening / closing valve 49 may be disposed on the downstream side (opening side) of the connection portion of the introduction pipe 45 with the exhaust circulation pipe 47. However, in this embodiment, the exhaust circulation pipe 47 of the introduction pipe 45 is disposed. It is provided in the connection part. The structures of the first on-off valve 48 and the second on-off valve 49 are not particularly limited, but in the present embodiment, the gas passing through the first on-off valve 48 and the second on-off valve 49 depending on the opening degree. The flow rate can be adjusted.

  As described above, the engine 10 according to the present embodiment includes the NOx storage catalyst 38 and the DPF 39, and introduces the introduction pipe 45, the supply pump 46, and the introduction pipe 45 for introducing the introduction gas containing outside air (oxygen) into the DPF 39. The exhaust gas recirculation pipe 47 for circulating the exhaust gas via the exhaust pipe, the first on-off valve 48 for opening and closing the exhaust gas circulation pipe 47, and the second on-off valve 49 for opening and closing the introduction pipe 45 are provided as the exhaust gas purification device 100. ing.

  The exhaust purification device 100 controls the operating state of the supply pump 46 at a predetermined timing when the regeneration process (S purge) of the NOx storage catalyst 38 is being performed, and the first on-off valve 48 and the second on-off valve 48. The open / close state of the on-off valve 49 is controlled. Specifically, while the first on-off valve 48 is closed, the second on-off valve 49 is opened and the supply pump 46 is operated. That is, the introduction pipe 45 is opened to the atmosphere while the exhaust circulation pipe 47 is shut off, and the supply pump 46 is operated. Thereby, the outside air as the introduction gas is supplied to the connection portion 26 a of the exhaust pipe 26 through the introduction pipe 45.

  At this time, although the pressure of the exhaust gas flowing through the connection portion 26a of the exhaust pipe 26 is higher than the atmospheric pressure, the introduction gas flowing through the introduction tube 45 is pumped and boosted by the supply pump 46, so the connection portion 26a of the exhaust pipe 26 Well supplied. The introduced gas (gas containing oxygen) supplied to the connection portion 26 a of the exhaust pipe 26 is introduced into the DPF 39 together with the exhaust gas flowing out from the NOx storage catalyst 38. Thereby, even when the exhaust air-fuel ratio of the NOx storage catalyst 38 is enriched (during catalyst regeneration), the exhaust air-fuel ratio of the DPF 39 is made lean. Further, the exhaust air-fuel ratio of the DPF 39 can be made lean regardless of the operating state of the engine 10.

  Accordingly, during the S purge of the NOx storage catalyst 38, the regeneration process of the DPF 39 can be simultaneously performed using the exhaust gas whose temperature has been raised for the S purge of the NOx storage catalyst 38. As a result, it is not necessary to inject fuel for DPF regeneration to raise the temperature of the exhaust gas, so that fuel consumption can be suppressed.

  The engine 10 includes an electronic control unit (ECU) 50. The ECU 50 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. It has been. The ECU 50 is supplied from various sensors including the intake pressure sensor (MAP sensor) 21, intake air temperature sensor 22, throttle position sensor (TPS) 36, air-fuel ratio sensors 40 and 41, temperature sensors 42 and 43, and the like. Based on the information, comprehensive control of the engine 10 is performed, and operations of the supply pump 46, the first on-off valve 48, and the second on-off valve 49 are also appropriately controlled. That is, the ECU 50 also functions as a part of the exhaust purification device 100 provided in the engine 10.

  Hereinafter, an example of the operation of the exhaust emission control device 100 included in the engine 10 according to the present embodiment, in particular, the operation during the regeneration process of the DPF 39 will be described.

  The ECU 50 includes an exhaust purification unit 53 including a catalyst regeneration processing unit 51 and a filter regeneration processing unit 52 (see FIG. 1). The catalyst regeneration processing unit 51 performs regeneration processing (NOx purge and S purge) of the NOx storage catalyst 38 at a predetermined timing. In addition, since the method of the regeneration process (NOx purge and S purge) of the NOx occlusion catalyst 38 by the catalyst regeneration processor 51 is an existing technique, a detailed description thereof is omitted here.

  The filter regeneration processing unit 52 executes the regeneration process (DPF regeneration) of the DPF 39 at the timing when the regeneration process (S purge) of the NOx storage catalyst 38 is being performed by the catalyst regeneration processing unit 51. Specifically, the filter regeneration processing unit 52 is provided near, for example, the temperature sensor 42 provided near the outlet of the NOx storage catalyst 38 or the outlet of the DPF 39 during the S purge of the NOx storage catalyst 38. Based on the detection result of the temperature sensor 43, it is determined whether or not the NOx storage catalyst 38 has risen to a predetermined first temperature (for example, 600 ° C.) or higher.

  Then, at the timing when the NOx storage catalyst 38 rises to the first temperature or higher, that is, at the timing when the exhaust gas temperature rises to such an extent that the regeneration process of the DPF 39 can be performed, the first on-off valve 48 and the first The open / close state of the second open / close valve 49 and the operating state of the supply pump 46 are appropriately controlled. Specifically, the first opening / closing valve 48 is closed, the second opening / closing valve 49 is opened, and the supply pump 46 is operated. In the present embodiment, both the first on-off valve 48 and the second on-off valve 49 are closed during normal times when the regeneration process of the DPF 39 is not performed. For this reason, the filter regeneration processing unit 52 opens the second on-off valve 49 at a predetermined opening while maintaining the closed state of the first on-off valve 48, and operates the supply pump 46 to operate the DPF. Start playback.

  As a result, as shown in FIG. 2A, the outside air passes through the second on-off valve 49 and flows into the introduction pipe 45. Since the first on-off valve 48 is closed, the exhaust gas in the exhaust pipe 26 does not flow into the introduction pipe 45 through the exhaust circulation pipe 47. The introduced gas, which is the inflowing outside air, is supplied to the connecting portion 26a of the exhaust pipe 26 through the introduction pipe 45, and the introduced gas is introduced into the DPF 39 together with the exhaust gas flowing out from the NOx storage catalyst 38. As the introduced gas is introduced into the DPF 39, the exhaust air-fuel ratio in the DPF 39 is made lean. As a result, the PM accumulated in the DPF 39 is burned and the DPF 39 is regenerated.

  During the regeneration process of the DPF 39, the filter regeneration processing unit 52 is connected via the introduction pipe 45 so that the exhaust air-fuel ratio of the DPF 39 is kept lean based on the detection result of the air-fuel ratio sensor 41, for example. The amount of introduced gas (air amount) supplied to the connection portion 26a of the exhaust pipe 26 is appropriately adjusted. Further, for example, the filter regeneration processing unit 52 appropriately controls the amount of introduced gas (air amount) supplied to the connection portion 26a of the exhaust pipe 26 so that the temperature of the DPF 39 does not excessively increase based on the detection result of the temperature sensor 43. To do. Specifically, it is preferable to appropriately adjust the amount of introduced gas so that the oxygen concentration of the gas introduced into the DPF 39 (mixed of introduced gas and exhaust gas) is about 5%. Thereby, PM in DPF39 can be burned stably. The method for adjusting the amount of introduced gas (air amount) is not particularly limited. For example, the output of the supply pump 46 may be changed, or the opening degree of the second on-off valve 49 may be changed. Good.

  Further, the filter regeneration processing unit 52 appropriately adjusts the amount of introduced gas supplied to the connecting portion 26a of the exhaust pipe 26 through the introduction pipe 45 as described above, but even in this case, the temperature of the DPF 39 is excessively high. There is a risk of rising. For this reason, when the temperature of the DPF 39 becomes equal to or higher than a second temperature (for example, about 700 ° C.) higher than the first temperature, the filter regeneration processing unit 52 performs the first opening and closing as shown in FIG. The valve 48 is opened at a predetermined opening, and the exhaust gas is caused to flow into the introduction pipe 45 through the exhaust circulation pipe 47. That is, the introduced gas including exhaust gas together with the outside air is supplied to the connection portion 26 a of the exhaust pipe 26. Thereby, the oxygen concentration of the introduced gas supplied to the connection part 26a of the exhaust pipe 26 is greatly reduced. As a result, the oxygen concentration of the gas introduced into the DPF 39 (a mixture of the introduced gas and the exhaust gas) is greatly reduced. Therefore, the combustion of PM in the DPF 39 is suppressed, and the temperature rise (overtemperature rise) of the DPF 39 can be suppressed.

  Furthermore, if the temperature rise (overtemperature rise) of the DPF 39 cannot be sufficiently suppressed only by opening the first on-off valve 48, the filter regeneration processing unit 52 blocks the flow of outside air into the introduction pipe 45. To do. That is, when the temperature of the DPF 39 reaches or exceeds a third temperature (for example, about 750 ° C.) higher than the second temperature, the filter regeneration processing unit 52, as shown in FIG. 49 is closed so that outside air does not flow into the introduction pipe 45. Thereby, the exhaust gas flowing into the introduction pipe 45 from the exhaust circulation pipe 47 is supplied to the connection portion 26a of the exhaust pipe 26 as the introduction gas. As a result, the oxygen concentration of the gas introduced into the DPF 39 (a mixture of the introduced gas and the exhaust gas) is further greatly reduced. Therefore, the combustion of PM in the DPF 39 is suppressed, and the temperature rise (overheating) of the DPF 39 can be more reliably suppressed.

  In addition, the filter regeneration processing unit 52 adjusts the oxygen concentration of the introduced gas according to the temperature of the DPF 39 as described above, and at the same time, the exhaust gas flowing out from the NOx storage catalyst 38 to the connection portion 26a of the exhaust pipe 26 is adjusted. The oxygen concentration may be adjusted. For example, when the temperature rise of the DPF 39 cannot be sufficiently suppressed only by adjusting the oxygen concentration of the introduced gas, for example, the fuel flows out from the NOx storage catalyst 38 by increasing the fuel injection amount or decreasing the intake amount. The oxygen concentration of the exhaust gas (exhaust gas flowing into the DPF 39) may be further enriched. Thereby, the temperature rise (overheating) of DPF39 can be controlled more certainly.

  After that, when the temperature of the DPF 39 becomes higher than the first temperature and lower than the fourth temperature (for example, about 650 ° C.) that is lower than the second temperature, as shown in FIG. Then, the first on-off valve 48 is closed to terminate the inflow of exhaust gas from the exhaust circulation pipe 47 to the introduction pipe 45. That is, the flow of the exhaust gas into the introduction pipe 45 is terminated when the temperature of the DPF 39 is sufficiently lowered so as not to be lower than the first temperature at which the filter regeneration can be performed. And the 2nd on-off valve 49 is opened as needed (refer Fig.2 (a)). Thereby, the regeneration process of DPF39 can be restarted at an early stage. At that time, it is preferable that the first on-off valve 48 is gradually closed step by step. Thereby, it is possible to suppress a rapid decrease in the temperature of the introduced gas, and hence a rapid decrease in the temperature of the DPF 39, and adjust the DPF 39 to an appropriate temperature.

As mentioned above, although one embodiment of the present invention was described, of course, the present invention is not limited to the above-described embodiment.
For example, in the above-described embodiment, a configuration in which the NOx storage catalyst and the DPF are housed in separate housings is illustrated, but the NOx storage catalyst and the DPF may be housed in one housing. Good.
For example, in the above-described embodiment, the present invention has been described by taking the exhaust purification device mounted on the diesel engine as an example. However, the present invention can of course be applied to the exhaust purification device mounted on the gasoline engine.

DESCRIPTION OF SYMBOLS 10 Engine 11 Engine main body 12 Cylinder head 13 Cylinder block 14 Piston 15 Connecting rod 16 Crankshaft 17 Combustion chamber 18 Intake port 19 Intake manifold 20 Intake pipe 21 Intake pressure sensor (MAP sensor)
DESCRIPTION OF SYMBOLS 22 Intake temperature sensor 23 Intake valve 24 Exhaust port 25 Exhaust manifold 26 Exhaust pipe 26a Connection part 27 Exhaust valve 30 Injector 32 Turbocharger 32a Turbine 32b Compressor 32c Turbine shaft 33 Air cleaner 34 Intercooler 35 Throttle valve 36 Throttle position sensor (TPS)
38 NOx storage catalyst 39 Diesel particulate filter (DPF)
40, 41 Air-fuel ratio sensor 42, 43 Temperature sensor 45 Introduction pipe (introduction passage)
46 Supply pump 47 Exhaust circulation piping (exhaust circulation passage)
48 1st on-off valve 49 2nd on-off valve 50 ECU
51 catalyst regeneration processing unit 52 filter regeneration processing unit 53 exhaust gas purification unit 100 exhaust gas purification device

Claims (6)

A NOx storage catalyst provided in the exhaust passage of the engine;
An exhaust purification device for an engine comprising: a particulate filter provided downstream of the NOx storage catalyst in the exhaust passage;
An introduction passage in which one end side is connected to a connection portion downstream of the NOx storage catalyst in the exhaust passage and upstream from the particulate filter, and the other end side is opened to the outside air and the outside air is introduced;
An exhaust circulation passage connecting the introduction passage and the downstream side of the exhaust passage with respect to the particulate filter;
A supply pump provided in the introduction passage;
A first on-off valve provided in the exhaust circulation passage for opening and closing the exhaust circulation passage;
An exhaust emission control device for an engine comprising: The exhaust emission control device for an engine according to claim 1,
A catalyst regeneration processing unit for performing regeneration processing of the NOx storage catalyst;
A filter regeneration processing unit that performs regeneration processing of the particulate filter at a timing when regeneration regeneration of the NOx storage catalyst is being performed by the catalyst regeneration processing unit,
The filter regeneration processing unit
The supply pump is operated at a timing when the temperature of the NOx storage catalyst rises to a first temperature or higher, and gas containing outside air is supplied to the connection portion of the exhaust passage through the introduction passage. Exhaust gas purification device for the engine. The exhaust emission control device for an engine according to claim 2,
The filter regeneration processing unit
When the temperature of the particulate filter becomes equal to or higher than a second temperature higher than the first temperature, the first on-off valve is opened, and the gas including the exhaust gas supplied from the exhaust circulation passage together with the outside air is introduced. An exhaust emission control device for an engine, characterized in that the exhaust gas is supplied to the connection portion of the exhaust passage through a passage. The engine exhaust gas purification apparatus according to claim 3,
A second on-off valve provided in the introduction passage to open and close the introduction passage;
The filter regeneration processing unit
When the temperature of the particulate filter becomes equal to or higher than a third temperature higher than the second temperature, the second on-off valve is closed, and a gas composed of exhaust gas supplied from the exhaust circulation passage is passed through the introduction passage. An exhaust purification device for an engine, characterized in that the exhaust gas is supplied to the connection portion of the exhaust passage. The engine exhaust gas purification apparatus according to claim 3 or 4,
The filter regeneration processing unit
When the temperature of the particulate filter is higher than the first temperature and lower than a fourth temperature that is lower than the second temperature, the first on-off valve is closed. Engine exhaust purification system. The engine exhaust gas purification apparatus according to claim 5,
The exhaust gas purification apparatus for an engine, wherein the filter regeneration processing unit gradually closes the first on-off valve.

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