JP2009144688A - Exhaust emission purifier of internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To suppress deterioration in fuel economy when simultaneously performing sulfur poisoning recovery treatment and filter regeneration treatment. <P>SOLUTION: An NOx occlusion reduction catalyst and a particulate filter are provided to the exhaust passage of the exhaust emission purifier of an internal combustion engine. The exhaust emission purifier is provided with a means of performing regeneration control, a calculation means, and a means of stopping regeneration control. The means of performing regeneration control includes the addition of fuel in the exhaust gas in order to perform simultaneously the sulfur poisoning recovery treatment of the NOx occlusion reduction catalyst and the filter regeneration treatment of the particulate filter. The calculation means calculates the value of a predetermined performance efficiency indicator based on the development situation of the sulfur poisoning recovery treatment so far from the beginning of the recovery control during the performance of the regeneration control this time. The predetermined performance efficiency indicator indicates the performance efficiency of the sulfur poisoning recovery treatment of the recovery control this time. The means of stopping recovery control stops the recovery control when the value of the performance efficiency indicator does not reach a predetermined reference after the completion of filter regeneration treatment when the sulfur poisoning recovery treatment has not been completed at the time of the completion of the filter regeneration treatment. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an exhaust gas purification apparatus for an internal combustion engine, and more particularly to an exhaust gas purification apparatus for an internal combustion engine in which a NOx storage reduction catalyst and a particulate filter are provided in an exhaust passage as a single body or separately.

  An NOx occlusion reduction catalyst for removing nitrogen oxides (NOx) contained in the exhaust gas is provided in the exhaust passage of the internal combustion engine, and a particulate filter for collecting exhaust particulates contained in the exhaust gas is provided. An exhaust emission control device is known.

  The NOx occlusion reduction catalyst as described above occludes NOx contained in exhaust gas when the air-fuel ratio of the inflowing exhaust gas is lean, the oxygen concentration in the inflowing exhaust gas decreases, and hydrocarbons in the exhaust gas If a reducing agent such as (HC) or carbon monoxide (CO) is present, the stored NOx is released and reduced and purified.

  Such NOx occlusion reduction catalyst is known to generate so-called sulfur poisoning in which the purification performance deteriorates due to occlusion of sulfur oxide (SOx) in the exhaust gas. In order to solve this problem, fuel is added on the upstream side of the NOx storage reduction catalyst to raise the temperature of the NOx storage reduction catalyst to a temperature at which SOx can be released (sulfur poisoning regeneration temperature) and the air-fuel ratio of the exhaust gas flowing in It is necessary to carry out a process (sulfur poisoning regeneration process) for releasing SOx by making the stoichiometric air-fuel ratio or richer than that.

  On the other hand, in the above particulate filter, if the amount of collected exhaust particulates increases, the back pressure in the exhaust system rises due to clogging of the particulate filter and the engine performance decreases, so the upstream side of the particulate filter In this case, it is necessary to carry out a process (filter regeneration process) for oxidizing and removing the collected exhaust particulates by adding fuel and raising the temperature of the particulate filter to the temperature at which the accumulated exhaust particulates burn (filter regeneration temperature). is there.

  As described above, when the sulfur poisoning regeneration process and the filter regeneration process are performed, fuel is added, so that the fuel consumption is worse than that during normal operation. Therefore, in the exhaust gas purification apparatus in which the NOx storage reduction catalyst and the particulate filter are provided in the exhaust passage, the sulfur poisoning regeneration process and the filter regeneration process are performed simultaneously to suppress deterioration in fuel consumption. (For example, refer to Patent Document 1).

JP 2005-344617 A JP 2005-299477 A JP 2003-336520 A JP 2007-198179 A

  However, even if the sulfur poisoning regeneration process and the filter regeneration process are performed at the same time as described above, the air-fuel ratio of the exhaust gas is actually made the stoichiometric air-fuel ratio or richer than that depending on, for example, engine operating conditions. Although the filter regeneration process proceeds, the sulfur poisoning regeneration process may not proceed well. In such a case, it takes time for the sulfur poisoning regeneration process to be completed, and as a result, deterioration of fuel consumption may not be sufficiently suppressed.

  The present invention has been made in view of such problems, and its purpose is to perform regeneration control including adding fuel to exhaust gas in order to simultaneously perform the sulfur poisoning regeneration process and the filter regeneration process. In the exhaust gas purification apparatus for an internal combustion engine to be implemented, it is to suppress deterioration in fuel consumption due to the execution of the regeneration control.

  The present invention provides an exhaust emission control device for an internal combustion engine described in each claim of the claims as means for solving the above-mentioned problems.

  The invention according to claim 1 is a sulfur poisoning regeneration process of the NOx occlusion reduction catalyst in an exhaust gas purification apparatus for an internal combustion engine in which the NOx occlusion reduction catalyst and the particulate filter are integrally or separately provided in the exhaust passage. And means for performing regeneration control including adding fuel to the exhaust gas in order to perform filter regeneration processing of the particulate filter at the same time, and during execution of the regeneration control, Based on the progress of the sulfur poisoning regeneration process, a means for calculating a value of a predetermined implementation efficiency index representing the efficiency of performing the sulfur poisoning regeneration process in the current regeneration control, and the sulfur upon completion of the filter regeneration process When the poisoning regeneration process is not completed, the value of the implementation efficiency index does not reach a predetermined standard after the filter regeneration process is completed. It is to provide an exhaust purification device of an internal combustion engine and means to stop the reproduction control when.

  That is, in the first aspect of the invention, when it is determined that it is not efficient to continue the regeneration control in order to perform only the sulfur poisoning regeneration process, the regeneration control is stopped. It has become. And by doing in this way, suppression of the fuel consumption deterioration by implementation of the said regeneration control can be aimed at.

  In particular, the present invention is based on the premise that the sulfur poisoning regeneration process and the filter regeneration process are performed simultaneously, and the calculation of the value of the implementation efficiency index used for determining whether to stop the regeneration control is at least the filter regeneration process. It is done during the implementation. Therefore, the fuel added during this period is not wasted because it is used for the filter regeneration process that needs to be carried out in the first place.

  On the other hand, in the case of determining whether to stop the regeneration control on the assumption that the sulfur poisoning regeneration process is performed alone, it takes a certain amount of time to appropriately calculate a value such as the above-described implementation efficiency index value of the present invention. Therefore, it may take a considerable amount of time to determine whether or not to stop the process. During the time required to determine whether or not to cancel, the sulfur poisoning regeneration process may not actually be performed. In some cases, the NOx occlusion reduction catalyst is completely wasted and an unnecessary heat load is applied to the NOx storage reduction catalyst. As described above, the present invention has an effect of improving fuel efficiency and suppressing thermal deterioration of the catalyst as compared with the case of determining whether to stop the regeneration control on the assumption that the sulfur poisoning regeneration process is performed alone.

According to a second aspect of the present invention, in the first aspect of the present invention, when the regeneration control is performed next after the regeneration control is stopped, the reference of the performance efficiency index is relaxed. It is like that.
According to the second aspect of the invention, sufficient sulfur poisoning regeneration processing can be performed more reliably.

According to a third aspect of the present invention, in the second aspect of the present invention, the reference of the execution efficiency index is the NOx occlusion reduction when the regeneration control is started next after the regeneration control is stopped. It is determined based on the SOx occlusion amount of the catalyst.
According to the third aspect of the invention, it is possible to set an appropriate standard for performing a sufficient sulfur poisoning regeneration process.

According to a fourth aspect of the present invention, in the invention according to any one of the first to third aspects, the value of the implementation efficiency index is at least the amount of fuel added and the amount of SOx released so far in the current regeneration control. It is calculated based on this.
According to the invention described in claim 4, the same effect as that of the invention described in claim 1 can be obtained.

  The invention described in each claim is directed to an exhaust gas purification apparatus for an internal combustion engine in which regeneration control including adding fuel to exhaust gas is performed in order to simultaneously perform the sulfur poisoning regeneration process and the filter regeneration process. There is a common effect that fuel consumption deterioration due to the execution of the regeneration control can be suppressed.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. FIG. 1 is a view for explaining a case where the present invention is applied to a compression ignition type internal combustion engine. The present invention can also be applied to other types of internal combustion engines. Referring to FIG. 1, 1 is an engine body, 2 is a combustion chamber of each cylinder, 3 is an electronically controlled fuel injection valve for injecting fuel into each combustion chamber 2, 4 is an intake manifold, and 5 is an exhaust manifold. Respectively.

  The intake manifold 4 is connected to the outlet of the compressor 7 a of the exhaust turbocharger 7 through the intake duct 6, and the inlet of the compressor 7 a is connected to the air cleaner 8. A throttle valve 9 driven by a step motor is arranged in the intake duct 6, and a cooling device (intercooler) 10 for cooling intake air flowing in the intake duct 6 is arranged around the intake duct 6. . In the embodiment shown in FIG. 1, the engine cooling water is guided into the intercooler 10 and the intake air is cooled by the engine cooling water. An air flow meter 21 for measuring the intake air amount is provided between the compressor 7a and the air cleaner 8.

  On the other hand, the exhaust manifold 5 is connected to the inlet of the exhaust turbine 7 b of the exhaust turbocharger 7, and the outlet of the exhaust turbine 7 b is connected to the casing 12 containing the NOx storage reduction catalyst 11. A temperature sensor 20 for detecting the temperature of the NOx storage reduction catalyst 11 is attached to the NOx storage reduction catalyst 11. The casing 12 containing the NOx occlusion reduction catalyst 11 is connected to a casing 24 containing a particulate filter 23 via a short exhaust pipe 22. A temperature sensor 25 for detecting the temperature of the particulate filter 23 is attached to the particulate filter 23. Thus, in the present embodiment, the NOx storage reduction catalyst and the particulate filter are provided separately. Further, a fuel addition valve 13 for adding fuel as a reducing agent to the exhaust gas flowing through the exhaust manifold 5 is disposed at the outlet of the collecting portion of the exhaust manifold 5.

  The exhaust manifold 5 and the intake manifold 4 are connected to each other via an exhaust gas recirculation (hereinafter referred to as EGR) passage 14, and an electronically controlled EGR control valve 15 is disposed in the EGR passage 14. A cooling device (EGR cooler) 16 for cooling the EGR gas flowing in the EGR passage 14 is disposed around the EGR passage 14. In the embodiment shown in FIG. 1, the engine cooling water is guided into the EGR cooler 16, and the EGR gas is cooled by the engine cooling water. On the other hand, each fuel injection valve 3 is connected to a fuel reservoir, so-called common rail 18 via a fuel supply pipe 17. Fuel is supplied into the common rail 18 from an electronically controlled fuel pump 19 with variable discharge amount, and the fuel supplied into the common rail 18 is supplied to the fuel injection valve 3 via each fuel supply pipe 17.

  The electronic control unit 30 is composed of a digital computer, and is connected to each other by a bidirectional bus 31. A ROM (Read Only Memory) 32, a RAM (Random Access Memory) 33, a CPU (Microprocessor) 34, an input port 35 and an output port 36. It comprises. Output signals from the temperature sensors 20 and 25 and the air flow meter 21 are input to the input port 35 via the corresponding AD converters 37. A load sensor 41 that generates an output voltage proportional to the accelerator opening is connected to the accelerator pedal 40, and the output voltage of the load sensor 41 is input to the input port 35 via the corresponding AD converter 37. Further, the input port 35 is connected to a crank angle sensor 42 that generates an output pulse every time the crankshaft rotates, for example, 15 °. On the other hand, the output port 36 is connected to the fuel injection valve 3, the throttle valve 9 driving step motor, the fuel addition valve 13, the EGR control valve 15, and the fuel pump 19 through corresponding drive circuits 38.

  As described above, the electronic control unit 30 is connected to various sensors and operating devices provided for controlling the internal combustion engine, and performs various controls necessary for the operation of the internal combustion engine by exchanging signals with them. It is supposed to be.

  By the way, the NOx occlusion reduction catalyst 11 used in the present embodiment is a known one, and when the air-fuel ratio of the inflowing exhaust gas is lean, the NOx contained in the exhaust gas is occluded and in the inflowing exhaust gas. If the oxygen concentration in the exhaust gas is reduced and a reducing agent such as HC or CO is present in the exhaust gas, the stored NOx is released and reduced and purified.

  Such NOx occlusion reduction catalyst is known to generate so-called sulfur poisoning in which the purification performance deteriorates due to occlusion of sulfur oxide (SOx) in the exhaust gas. In order to solve this problem, fuel is added on the upstream side of the NOx storage reduction catalyst to raise the temperature of the NOx storage reduction catalyst to a temperature at which SOx can be released (sulfur poisoning regeneration temperature) and the air-fuel ratio of the exhaust gas flowing in It is necessary to carry out a process (sulfur poisoning regeneration process) for releasing SOx by making the stoichiometric air-fuel ratio or richer than that.

  The particulate filter 23 used in the present embodiment is also a known filter for collecting exhaust particulates contained in the exhaust gas. For such a particulate filter, when the amount of collected exhaust particulates increases, the back pressure in the exhaust system rises due to clogging of the particulate filter and the engine performance decreases, so the upstream of the particulate filter It is necessary to add fuel on the side and raise the temperature of the particulate filter to the temperature at which the accumulated exhaust particulates burn (filter regeneration temperature) to oxidize and remove the collected exhaust particulates (filter regeneration treatment) There is.

  As described above, also in this embodiment, the sulfur poisoning regeneration process and the filter regeneration process are performed as necessary. That is, in this embodiment, the SOx amount (SOx occlusion amount) occluded in the NOx occlusion reduction catalyst 11 and the exhaust particulate amount (deposited exhaust particulate amount) accumulated in the particulate filter 23 are estimated. The sulfur poisoning regeneration process and the filter regeneration process are performed according to the estimated value. Various methods for estimating the SOx occlusion amount and the amount of deposited exhaust particulate matter are known, and detailed description thereof will be omitted here. For example, the operating state history including the engine speed, the fuel injection amount, etc. Further, it can be estimated from the sulfur poisoning regeneration process and the filter regeneration process, which are obtained from the temperature of the NOx storage reduction catalyst and the particulate filter, the history of the air-fuel ratio of the exhaust gas, and the like.

  In more detail, in the present embodiment, when the amount of deposited exhaust particulates is equal to or greater than a predetermined amount necessary for the filter regeneration process, and the SOx occlusion amount at that time is equal to or greater than the minimum sulfur poisoning regeneration process execution amount, Regeneration control for adding fuel to the exhaust gas is performed so that the poison regeneration process and the filter regeneration process are simultaneously performed. On the other hand, if the SOx occlusion amount is less than the minimum sulfur poisoning regeneration processing execution amount when the amount of accumulated exhaust particulates exceeds the predetermined filter regeneration processing required amount, the exhaust gas is only subjected to the filter regeneration processing. Filter individual regeneration control for adding fuel therein is implemented.

  That is, in this embodiment, the sulfur poisoning regeneration process and the filter regeneration process are performed simultaneously, or only the filter regeneration process is performed independently. When the regeneration control is performed as described above, fuel is added, so that the fuel consumption is worse than that during normal operation. In this way, the sulfur poisoning regeneration process is performed in the filter. By performing the regeneration process at the same time, in this embodiment, for example, the heat generated in the NOx occlusion reduction catalyst 11 on the upstream side during the regeneration control can be used for raising the temperature of the particulate filter 23 on the downstream side. For example, the deterioration of fuel consumption can be suppressed.

  On the other hand, from the viewpoint of suppressing the deterioration of fuel consumption as described above, even if the sulfur poisoning regeneration process and the filter regeneration process are performed at the same time, there may be cases where it cannot actually be performed depending on the engine operating conditions. That is, the temperature of the NOx occlusion reduction catalyst and the temperature of the particulate filter are set to temperatures appropriate for the sulfur poisoning regeneration process and the filter regeneration process, respectively, depending on engine operating conditions, for example, when rapid acceleration and rapid deceleration are repeated. However, it may be difficult to make the air-fuel ratio of the exhaust gas richer than the stoichiometric air-fuel ratio or higher. In such a case, although the filter regeneration process proceeds, the sulfur poisoning regeneration process does not proceed well, and it takes time to complete the sulfur poisoning regeneration process, and as a result, suppression of deterioration in fuel consumption is sufficiently achieved. It becomes impossible to plan.

  Therefore, in the present embodiment, in consideration of such a situation, control as described below is performed, and fuel is added to the exhaust gas in order to perform the sulfur poisoning regeneration process and the filter regeneration process simultaneously. When the regeneration control including this is performed, fuel consumption deterioration due to the implementation of the regeneration control is suppressed.

  Hereinafter, an example of a specific method for realizing this control will be described with reference to FIG. FIG. 2 is a flowchart showing a control routine for carrying out this control. This control routine is started at the same time when the electronic control unit 30 starts the regeneration control for adding fuel to the exhaust gas so that the sulfur poisoning regeneration process and the filter regeneration process are simultaneously performed. When this control routine starts, first, in step 101, the value Ei of the execution efficiency index indicating the execution efficiency of the sulfur poisoning regeneration process in the current regeneration control is the progress of the sulfur poisoning regeneration process so far in the current regeneration control. Calculated based on the situation.

  Here, the implementation efficiency index is an index representing the implementation efficiency of the sulfur poisoning regeneration process in this regeneration control (that is, how much the sulfur poisoning regeneration process has progressed due to how much fuel consumption has deteriorated). What is necessary is just to predetermine from such things. That is, the implementation efficiency index is, for example, a value obtained by dividing the previous SOx release amount in the current regeneration control by the amount of added fuel (SOx release amount per unit added fuel amount), or the progress until that time in the current regeneration control. The ratio of the time when the temperature of the NOx occlusion reducing agent with respect to time becomes the sulfur poisoning regeneration temperature and the air-fuel ratio of the exhaust gas is richer than the stoichiometric air-fuel ratio (ratio of SOx release time) or the like may be used. Further, the distance traveled by the vehicle from the end of the previous regeneration control to the completion of the current regeneration control (that is, the completion of the sulfur poisoning regeneration process) is estimated, and the fuel consumption per unit vehicle travel distance ( The average unit fuel consumption) may be used as the implementation efficiency index. The greater the average unit fuel consumption, the greater the degree of fuel consumption deterioration due to the execution of the regeneration control. In addition, since the calculation method of this average unit fuel consumption is well-known (for example, refer patent document 4), detailed description is abbreviate | omitted here.

  In the present embodiment, the average unit fuel consumption is used as the execution efficiency index. In step 101, the progress of the sulfur poisoning regeneration process so far in the current regeneration control (for example, SOx release amount, added fuel) The average unit fuel consumption estimated at that time based on the operation status (for example, in-cylinder injection amount, etc.) from the end of the previous regeneration control to the start of the current regeneration control. The amount is calculated as an implementation efficiency index value Ei.

  When the execution efficiency index value Ei is calculated in step 101, the process proceeds to step 102. In step 102, it is determined whether or not a condition for completing the filter regeneration process is satisfied. In the present embodiment, when the amount of accumulated exhaust particulates of the particulate filter 23 is equal to or less than a predetermined amount of filter regeneration processing completion, it is determined that the filter regeneration processing completion condition is satisfied, and the particulates If the amount of particulate exhaust gas accumulated in the filter 23 is larger than the predetermined amount of filter regeneration processing, it is determined that the filter regeneration processing completion condition is not satisfied.

  If it is determined in step 102 that the filter regeneration processing completion condition is not satisfied, the routine proceeds to step 105, where regeneration control is continued, and control from step 101 is performed again. On the other hand, if it is determined in step 102 that the filter regeneration processing completion condition is satisfied, the process proceeds to step 103.

  In step 103, it is determined whether or not the completion condition for the sulfur poisoning regeneration process is satisfied. In the present embodiment, when the SOx occlusion amount of the NOx occlusion reduction catalyst 11 is equal to or less than a predetermined sulfur poisoning regeneration process completion amount, it is determined that the completion condition for the sulfur poisoning regeneration process is satisfied. When the SOx occlusion amount of the NOx occlusion reduction catalyst 11 is larger than the predetermined sulfur poisoning regeneration process completion amount, it is determined that the completion condition for the sulfur poisoning regeneration process is not satisfied.

  When it is determined in step 103 that the completion condition for the sulfur poisoning regeneration process is satisfied, the routine proceeds to step 104, where regeneration control is completed, and this control routine ends. On the other hand, if it is determined in step 103 that the completion condition for the sulfur poisoning regeneration process is not satisfied, the process proceeds to step 106.

  In step 106, it is determined whether or not the value Ei of the implementation efficiency index has reached a predetermined standard. More specifically, since the average unit fuel consumption is used as the implementation efficiency index in the present embodiment as described above, the average unit fuel consumption value Ei calculated in step 101 is determined in advance here. It is determined whether or not the average unit fuel consumption is below the reference value. Here, the reference value of the average unit fuel consumption is set as a value indicating the allowable limit of fuel consumption deterioration in the regeneration control. In addition, when using things other than average unit fuel consumption as said implementation efficiency parameter | index, the reference value or reference | standard corresponding to the implementation efficiency parameter | index used from the same viewpoint is set.

  When it is determined in step 106 that the value Ei of the implementation efficiency index does not reach the predetermined reference, that is, the average unit fuel consumption value Ei is larger than the predetermined average unit fuel consumption reference value, Since it is determined that the degree of fuel consumption deterioration in the regeneration control is outside the allowable range, in this case, the routine proceeds to step 109 where the regeneration control is stopped and the present control routine ends.

  On the other hand, in step 106, it is determined that the value Ei of the implementation efficiency index has reached a predetermined reference, that is, the value Ei of the average unit fuel consumption is equal to or less than the reference value of the predetermined average unit fuel consumption. In this case, since it is determined that the degree of deterioration of fuel consumption in the regeneration control is within the allowable range, in this case, the process proceeds to step 107 and the regeneration control is continued. In step 108, the execution efficiency index value Ei is calculated, and the control from step 106 is executed again. That is, while the regeneration control is continued, the execution efficiency index value Ei is monitored, and when it is determined that the predetermined standard is not reached, the regeneration control is stopped at that time.

  As understood from the above description, in the present embodiment, fuel is added to the exhaust gas in order to simultaneously perform the sulfur poisoning regeneration process of the NOx storage reduction catalyst 11 and the filter regeneration process of the particulate filter 23. During the execution of the regeneration control including performing a predetermined execution efficiency representing the efficiency of performing the sulfur poisoning regeneration process in the current regeneration control based on the progress status of the sulfur poisoning regeneration process so far in the current regeneration control When an index value is calculated and the sulfur poisoning regeneration process is not completed when the filter regeneration process is completed, and the implementation efficiency index value does not reach a predetermined standard after the filter regeneration process is completed. The reproduction control is canceled.

  That is, in this embodiment, the regeneration control is stopped when it is determined that it is not efficient to continue the regeneration control only for the sulfur poisoning regeneration process. By doing so, it is possible to suppress deterioration in fuel consumption due to the execution of regeneration control. In particular, the present embodiment is premised on performing the sulfur poisoning regeneration process and the filter regeneration process at the same time, and the calculation of the value of the implementation efficiency index used for determining whether to stop the regeneration control is at least the filter regeneration process. It is to be done during the implementation of. Therefore, since the fuel added during this period is used for the filter regeneration process that needs to be performed in the first place, it is not wasted.

  On the other hand, when determining whether to stop the regeneration control on the assumption that the sulfur poisoning regeneration process is performed alone, a certain amount of time is required to appropriately calculate a value such as the implementation efficiency index value in the present embodiment. Therefore, the stop determination takes a corresponding time. In this case, the sulfur poisoning regeneration process may not actually be performed during the time required for the stop determination. May be wasted at all, and may result in unnecessary heat load being applied to the NOx storage reduction catalyst. For this reason, according to the present embodiment, the fuel consumption is improved and the thermal deterioration of the catalyst is suppressed as compared with the case where the regeneration control stop determination is made on the assumption that the sulfur poisoning regeneration process is performed alone. I can say that.

  In another embodiment of the present invention, when the regeneration control is performed next after the regeneration control is stopped, the criterion of the implementation efficiency index used in step 106 is relaxed. It may be. That is, when the average unit fuel consumption is used as the implementation efficiency index as in the above-described embodiment, the reference value is increased.

  In this case, for example, the reference is determined based on the SOx storage amount of the NOx storage reduction catalyst when the regeneration control is started next after the regeneration control is stopped. May be. That is, the standard is relaxed as the SOx occlusion amount of the NOx occlusion reduction catalyst increases. That is, when the average unit fuel consumption is used as the execution efficiency index as in the above-described embodiment, the reference value is increased as the SOx storage amount of the NOx storage reduction catalyst increases. .

  This is because when the reproduction control is started next after the reproduction control is stopped, the reproduction control is completed without being stopped and then the reproduction control is started. This is because the amount of SOx occluded in the NOx occlusion reduction catalyst is considered to be larger than that of NOx. For this reason, by relaxing the above-mentioned standard as described above, a sufficient sulfur poisoning regeneration process can be performed more reliably. In addition, as described above, if the reference is determined based on the SOx storage amount of the NOx storage reduction catalyst, it is possible to set an appropriate reference for performing a sufficient sulfur poisoning regeneration process. It becomes.

  In the above, the case where the particulate filter is provided downstream of the NOx storage reduction catalyst in the exhaust passage has been described as an example, but the present invention is not limited to this, and the sulfur of the NOx storage reduction catalyst When regeneration control including addition of fuel to exhaust gas is performed in order to perform poisoning regeneration processing and filter regeneration processing of the particulate filter at the same time, it may be applied to other configurations. it can. Therefore, for example, the present invention can also be applied to a case where the NOx storage reduction catalyst and the particulate filter are integrally provided in the exhaust passage, or a case where the NOx storage reduction catalyst is provided downstream of the particulate filter in the exhaust passage. it can.

  Further, in the above description, a fuel addition valve is provided at the outlet of the exhaust manifold, thereby adding fuel to the exhaust gas. However, the position of the fuel addition valve is different from that of the NOx storage reduction catalyst and the catalyst in the exhaust passage. Other positions may be used as long as they are upstream from the curate filter. Further, the fuel may be added by a method of injecting fuel into the cylinder during the exhaust stroke of each cylinder of the internal combustion engine (so-called post injection method).

FIG. 1 is a view for explaining a case where the present invention is applied to a compression ignition type internal combustion engine. FIG. 2 is a flowchart showing a control routine of control that can be performed by the exhaust gas purification apparatus for an internal combustion engine according to the embodiment of the present invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 3 Fuel injection valve 4 Intake manifold 5 Exhaust manifold 7 Exhaust turbocharger 11 NOx storage reduction catalyst 13 Fuel addition valve 21 Air flow meter 23 Particulate filter

Claims (4)

In the exhaust gas purification apparatus for an internal combustion engine in which the NOx storage reduction catalyst and the particulate filter are provided in the exhaust passage integrally or separately from each other,
Means for performing regeneration control including adding fuel to exhaust gas to simultaneously perform sulfur poisoning regeneration processing of the NOx storage reduction catalyst and filter regeneration processing of the particulate filter;
During the execution of the regeneration control, based on the progress status of the sulfur poisoning regeneration process so far in the current regeneration control, a predetermined implementation efficiency index representing the efficiency of performing the sulfur poisoning regeneration process in the current regeneration control Means for calculating the value;
If the sulfur poisoning regeneration process is not completed when the filter regeneration process is completed, the regeneration control is stopped if the value of the implementation efficiency index does not reach a predetermined standard after the filter regeneration process is completed. And an exhaust emission control device for an internal combustion engine.   The exhaust emission control device for an internal combustion engine according to claim 1, wherein, when the regeneration control is executed next after the regeneration control is stopped, the reference of the implementation efficiency index is relaxed.   The said reference | standard of the said implementation efficiency parameter | index is determined based on the SOx occlusion amount of the said NOx storage reduction catalyst when the said regeneration control is started next after the said regeneration control is stopped. Exhaust gas purification device for internal combustion engine.   The exhaust purification of the internal combustion engine according to any one of claims 1 to 3, wherein the value of the implementation efficiency index is calculated based on at least the amount of fuel added so far and the amount of SOx released in the current regeneration control. apparatus.

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