JP2007291970A - Exhaust emission control device of internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an exhaust emission control device of an internal combustion engine enabling a reduction in the amount of a reducer consumed for regeneration by suppressing the wasteful addition of the reducer into an exhaust emission control catalyst. <P>SOLUTION: This exhaust emission control device of an internal combustion engine comprises a storage/reduction NOx catalyst 8 installed in the exhaust passage 4 of the internal combustion engine 1 and a fuel adding valve 10 for adding a fuel serving as a reducer from the upstream side of the NOx catalyst 8. When an ECU 20 determines that predetermined requirements for regeneration execution which includes that the operating conditions of the internal combustion engine 1 are within a predetermined operating area suitable for the regeneration of the NOx catalyst 8 are established, it performs the regeneration of the NOx catalyst 8. When the predetermined requirements for regeneration execution are established, the ECU 20 predicts the operating conditions of the internal combustion engine 1 after a predetermined time is passed after the time when these requirements are established, and according to these predicted operating conditions, controls the operation of the fuel adding valve 10. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an exhaust gas purification apparatus for an internal combustion engine having a regenerative exhaust purification catalyst in an exhaust passage.

  The NOx storage reduction catalyst used as an exhaust gas purification means for an internal combustion engine has a reduced catalyst function due to the accumulation of sulfur oxides contained in the exhaust gas. For this reason, when using an NOx storage reduction catalyst, it is necessary to periodically perform a regeneration process called S regeneration in order to decompose and remove sulfur oxides deposited on the catalyst to restore the catalyst function. . In the S regeneration, the catalyst temperature is raised to a target temperature (for example, 600 ° C. or higher) higher than the temperature range in the normal operation state, and the air-fuel ratio in the vicinity of the catalyst is made richer than the stoichiometric air-fuel ratio or the stoichiometric air-fuel ratio. It is implemented by holding. The control of the air-fuel ratio in the vicinity of the catalyst is achieved by adding fuel as a reducing agent in the exhaust, and the temperature rise of the catalyst is caused by burning the fuel added as the reducing agent in the catalyst, or the air-fuel ratio of the internal combustion engine is made higher than the stoichiometric air-fuel ratio. Also, the fuel is injected into the cylinder in a rich state and burned by the catalyst. At this time, depending on the operating state of the internal combustion engine before executing the S regeneration, the catalyst temperature may excessively increase during the S regeneration. Therefore, one or more of the rotational speed of the internal combustion engine, the load of the internal combustion engine, the accelerator opening, and the speed of the vehicle in which the internal combustion engine is mounted is detected, and the detected rotational speed of the internal combustion engine, Catalyst control for limiting fuel addition when one or more of the load of the internal combustion engine, the accelerator opening, and the speed of the vehicle in which the internal combustion engine is mounted show a lower reduction level than the reference reduction degree An apparatus is known (see Patent Document 1). In addition, there is Patent Document 2 as a prior art document related to the present invention.

JP 2005-90276 A JP 2004-251172 A

  When the S regeneration of the NOx storage reduction catalyst is performed, the amount of fuel supplied to the cylinder of the internal combustion engine is changed, so that the operating state of the internal combustion engine suitable for performing the S regeneration is limited. For this reason, for example, in an operation transition period in which the operating state of the internal combustion engine is likely to change, there is a possibility that the S regeneration is performed only for a short time even if the S regeneration is started with the operating state suitable for the S regeneration. In this case, since the number of times of S regeneration increases, for example, S regeneration is executed again after the operating state of the internal combustion engine becomes stable, there is a risk that the amount of fuel consumed in S regeneration will increase. In the catalyst control device of Patent Document 1, the fuel addition is controlled based on a plurality of determination parameters such as the rotational speed and load of the internal combustion engine. However, in this control, the execution time of S regeneration is insufficient, and one S regeneration is performed. The catalyst may not be properly regenerated. Therefore, there is a possibility that useless fuel is added to the catalyst.

  Therefore, an object of the present invention is to provide an exhaust purification device for an internal combustion engine that can suppress useless addition of a reducing agent to an exhaust purification catalyst and reduce the amount of reducing agent consumed in regeneration processing. To do.

  An exhaust gas purification apparatus for an internal combustion engine according to the present invention includes a regenerative exhaust purification catalyst provided in an exhaust passage of the internal combustion engine, a reducing agent addition means for adding a reducing agent from an upstream side of the exhaust purification catalyst, An operation state acquisition means for acquiring an operation state, and a predetermined regeneration execution including that the operation state acquired by the operation state acquisition means is an operation state within a predetermined operation region suitable for the regeneration process of the exhaust purification catalyst. In the exhaust gas purification apparatus for an internal combustion engine, comprising: a catalyst regeneration executing means for adding a reducing agent from the reducing agent adding means and executing a regeneration process of the exhaust purification catalyst when it is determined that a condition is satisfied. When the predetermined regeneration execution condition is satisfied, the regeneration execution means predicts the operation state of the internal combustion engine after a predetermined time has elapsed from the time when the predetermined regeneration execution condition is satisfied. The above-described problem is solved by comprising measuring means and operation control means for controlling the operation of the reducing agent adding means based on the operating state predicted by the operating state predicting means. ).

  According to the exhaust gas purification apparatus for an internal combustion engine of the present invention, the operating state of the internal combustion engine after a predetermined time has elapsed from the time when the predetermined regeneration execution condition is satisfied, and the reducing agent adding means is based on the predicted operating state. Since the operation is controlled, for example, the addition of fuel can be prohibited when the operation state of the internal combustion engine after the elapse of a predetermined time is outside a predetermined operation region. Therefore, useless addition of a reducing agent to the exhaust purification catalyst can be suppressed, and the consumption of the reducing agent used for the regeneration process can be reduced.

  In one embodiment of the present invention, when the predetermined regeneration execution condition is satisfied, the operating state prediction means is configured to perform the predetermined operation based on a history of the operation state of the internal combustion engine up to a point in time when the predetermined regeneration execution condition is satisfied. Predicting the operation state of the internal combustion engine after the predetermined time has elapsed from the time when the regeneration execution condition is satisfied, and the operation control means is configured such that the operation state predicted by the operation state prediction means is the predetermined operation region. In the case of an external operating state, the operation of the reducing agent adding means may be controlled so that the addition of the reducing agent from the reducing agent adding means is restricted (Claim 2). When it is predicted that the operating state after a predetermined time has elapsed from when the predetermined regeneration execution condition is satisfied, the operating state of the internal combustion engine is within the predetermined operating region during the predetermined time. It can be expected that the operating state changes from the operating state to an operating state outside the predetermined operating range. When the operating state of the internal combustion engine changes in this way, even if the addition of the reducing agent is started when the predetermined regeneration execution condition is satisfied, the operating state of the internal combustion engine is changed to the predetermined operation before the exhaust purification catalyst is properly regenerated. There is a possibility that the regeneration process of the exhaust purification catalyst may be interrupted because it falls outside the region. In this case, it is necessary to regenerate the exhaust purification catalyst again, and there is a risk of using an extra reducing agent. In this embodiment, when the operation state after a predetermined time elapses from when the predetermined regeneration execution condition is satisfied is outside the predetermined operation region, fuel addition is restricted, so that wasteful use of reducing agent can be suppressed.

  In one embodiment of the present invention, the operation state prediction means includes a plurality of determination regions set so as not to overlap each other within the predetermined operation region and the operation state of the internal combustion engine from the operation state in each determination region. Storage means for storing a map that associates durations that are expected to be maintained in an operation state within a predetermined operation region is provided, and the operation control means satisfies the predetermined regeneration execution condition In this case, referring to the map, it is determined whether the operation state of the internal combustion engine at the time when the predetermined regeneration execution condition is satisfied is the operation state of the determination region of the plurality of determination regions, and the determination result is The duration of the reducing agent adding means is obtained so that the addition of the reducing agent from the reducing agent adding means is limited when the duration is less than the predetermined time. It is your good (claim 3). In this embodiment, since the duration is acquired based on the operating state of the internal combustion engine at the time when the predetermined regeneration execution condition is established, the duration can be easily acquired. Further, if this duration is less than the predetermined time, in other words, if the operating state of the internal combustion engine is expected to be out of the predetermined operating range during the predetermined time, the addition of the reducing agent is limited, so It is possible to suppress useless addition of a reducing agent to the catalyst.

  In this embodiment, the operating state predicting unit acquires time when the operating state of the internal combustion engine is actually maintained in the predetermined operating region from the operating state of each determination region, and the time acquiring unit Learning means for correcting a correspondence relationship between the plurality of determination areas and the duration time based on the time acquired by (5). In this case, the correspondence relationship between the plurality of determination regions and the duration time can be updated to a correspondence relationship reflecting the operation history of each internal combustion engine. As a result, the duration time can be obtained with high accuracy based on the operating state of the internal combustion engine when the predetermined regeneration execution condition is satisfied. Therefore, useless addition of a reducing agent can be further suppressed.

  In one form of the present invention, the exhaust purification catalyst is an NOx storage reduction catalyst, and the fuel for the internal combustion engine may be added as a reducing agent from the reducing agent adding means. The NOx storage reduction catalyst has a limited operating state suitable for performing S regeneration. Therefore, useless fuel addition can be suppressed by applying the present invention.

  In the present invention, the NOx storage reduction catalyst may be any catalyst as long as it can hold NOx in the catalyst, and whether it is absorbed or adsorbed is not limited by the term of storage.

  As described above, according to the present invention, the operating state of the internal combustion engine after a predetermined time has elapsed from the time when the predetermined regeneration execution condition is satisfied is predicted, and according to the predicted operating state of the internal combustion engine. Since the addition of the reducing agent is controlled, useless addition of the reducing agent to the exhaust purification catalyst can be suppressed. Therefore, the consumption of the reducing agent used for the regeneration treatment of the exhaust purification catalyst can be reduced.

(First form)
FIG. 1 shows an internal combustion engine in which an exhaust emission control device according to a first embodiment of the present invention is incorporated. An internal combustion engine (hereinafter also referred to as an engine) 1 in FIG. 1 is a diesel engine, which is mounted on a vehicle as a driving power source, and includes a plurality of (four in FIG. 1) cylinders 2, An intake passage 3 and an exhaust passage 4 connected to the cylinder 2 are provided. The intake passage 3 is provided with an air filter 5 for filtering the intake air, a compressor 6a of the turbocharger 6 and an intake throttle valve 7 for adjusting the intake air amount, and a turbine 6b of the turbocharger 6 is provided in the exhaust passage 4. ing. An exhaust purification unit 9 including an NOx storage reduction catalyst (hereinafter also abbreviated as NOx catalyst) 8 as an exhaust purification catalyst on the downstream side of the turbine 6 b in the exhaust passage 4, and the NOx catalyst 8 A fuel addition valve 10 serving as a reducing agent adding means for adding fuel as a reducing agent is provided upstream. The exhaust passage 4 and the intake passage 3 are connected by an EGR passage 11, and an EGR cooler 12 and an EGR valve 13 are provided in the EGR passage 11.

  The fuel addition valve 10 is provided in order to add a fuel upstream of the NOx catalyst 8 and generate a reducing atmosphere necessary for releasing NOx absorbed by the NOx catalyst 8 and S regeneration of the NOx catalyst 8. . The operation of the fuel addition valve 10 is controlled by an engine control unit (ECU) 20. The ECU 20 is configured as a computer including a microprocessor and peripheral devices such as RAM and ROM necessary for its operation, and an injector 30 for injecting fuel into the cylinder 2 and a common rail for storing high-pressure fuel supplied to the injector 30 This is a well-known computer unit that operates various devices such as a pressure regulating valve 31 to control the operating state of the engine 1. For example, the ECU 20 calculates the amount of fuel to be injected from the injector 30 based on the operating state of the engine 1, and controls the operation of the injector 30 so that the calculated amount of fuel is injected. Hereinafter, this control may be referred to as normal control. For example, when performing the S regeneration of the NOx catalyst 8, the ECU 20 masses the amount of air sucked into the engine 1 and the fuel injected from the injector 30 in order to raise the NOx catalyst 8 to the target temperature during the S regeneration. The operation of the injector 30 is controlled so that the air-fuel ratio given as the ratio becomes richer than the stoichiometric air-fuel ratio. Hereinafter, controlling the air-fuel ratio to be richer than the stoichiometric air-fuel ratio in this way is referred to as air-fuel ratio rich control. Various sensors such as a crank angle sensor 21 that outputs a signal corresponding to the crank angle of the engine 1 are connected to the ECU 20 as means for detecting various physical quantities or state quantities to be referred to in such control. .

  FIG. 2 shows an S regeneration control routine that the ECU 20 executes to perform S regeneration of the NOx catalyst 8. The control routine of FIG. 2 is repeatedly executed at a predetermined cycle while the engine 1 is operating. Note that by executing the control routine of FIG. 2, the ECU 20 functions as the catalyst regeneration execution means of the present invention.

  In the control routine of FIG. 2, the ECU 20 first obtains the current rotational speed N of the engine 1 and the fuel injection amount Q injected from the current injector 30 in step S11. In the present invention, since the operating state of the engine 1 is specified by the rotational speed N and the fuel injection amount Q, these may be referred to as the operating state of the engine 1. In subsequent step S12, the ECU 20 updates the history of the operating state of the engine 1. In the RAM of the ECU 20, a plurality (for example, 20) of the number of revolutions of the engine 1 and the fuel injection amount up to the present are stored at predetermined time intervals (for example, 0.1 second intervals). In this process, when a predetermined time interval has elapsed since the operation history of the engine 1 was updated last time, the oldest operation state of the engine 1 stored in the ECU 20 is cleared, and in step S11. The acquired current engine speed N and fuel injection amount Q are stored in the ECU 20 as the newest operating state. In this way, the operation history of the engine 1 is updated. Note that the predetermined time interval and the number of operation histories stored in the ECU 20 may be appropriately changed according to the performance of the ECU 20 and the like.

  In the next step S13, the ECU 20 determines whether or not S regeneration of the NOx catalyst 8 is requested. S regeneration of the NOx catalyst 8 is required when the S poison amount of the NOx catalyst 8 is equal to or greater than a predetermined amount set in advance. The S poison amount of the NOx catalyst 8 may be estimated by a known estimation method. For example, the NOx catalyst estimated based on the amount of sulfur (S) flowing into the NOx catalyst 8 estimated based on the amount of fuel injected from the injector 30 and the amount of fuel added from the fuel addition valve 10 during S regeneration. The amount of S poisoning is estimated by adding and subtracting the amount of S released from 8.

  If it is determined that S regeneration of the NOx catalyst 8 is requested, the process proceeds to step S14, where the ECU 20 determines a predetermined operation region in which the current operation state of the engine 1 is suitable for execution of air-fuel ratio rich control (hereinafter referred to as S regeneration operation). It is determined whether or not it is in an operating state within a range. The operating state suitable for executing the air-fuel ratio rich control is limited. For example, if air-fuel ratio rich control is performed during idle operation, fuel cut operation in which fuel injection from the injector 30 is stopped, sudden acceleration, sudden deceleration, etc., the output of the engine 1 may become unstable. In these operating states, normal control is performed. FIG. 3 shows an example of the relationship between the rotational speed and fuel injection amount of the engine 1 and the S regeneration operation region. In FIG. 3, the region A specified by the rotational speeds N1 and N2 and the fuel injection amounts Q1 and Q2 is the S regeneration operation region. The relationship shown in FIG. 3 is obtained by, for example, experiments in advance and stored in the ECU 20 as a map. The ECU 20 determines whether or not the operation state of the engine 1 is an operation state within the S regeneration operation region based on this map and the current operation state of the engine 1.

  If it is determined that the current operating state of the engine 1 is the operating state within the S regeneration operation region, the process proceeds to step S15, where the ECU 20 is the operating state of the engine 1 after a predetermined time from the present, for example, t seconds, i. A subsequent engine speed N [t] and a fuel injection amount Q [t] after t seconds from the present time are predicted. In this t seconds, when S regeneration is performed on the NOx catalyst 8, the time during which this S regeneration process effectively acts on the NOx catalyst 8, in other words, at least in order to efficiently perform S regeneration. A necessary time (hereinafter also referred to as a minimum rich addition time) is set. For example, 2 seconds is set as the minimum rich addition time. A method of predicting the engine speed N [t] after t seconds from the present will be described with reference to FIG. FIG. 4 shows an example of the temporal change in the rotational speed of the engine 1, and the line L in FIG. 4 shows the change in the rotational speed of the engine 1 from t seconds before to the present. Further, a range B sandwiched between the rotational speed N1 and the rotational speed N2 in FIG. 4 indicates the S regeneration operation region. When the rotational speed of the engine 1 changes as indicated by the line L in FIG. 4, the rotational speed of the engine 1 is determined from the current rotational speed N to the rotational speed N [−t] from t seconds ago to the present. ], Which is a value obtained by subtracting []. Therefore, after t seconds from the present time, it can be predicted that the rotational speed of the engine 1 becomes the rotational speed N [t] obtained by adding the rotational speed difference ΔN to the current rotational speed N. That is, since the rotational speed of the engine 1 has changed as indicated by the arrow A1 in FIG. 4 during t seconds up to the present, it can be predicted that the change will occur as indicated by the arrow A2 in FIG. 4 after t seconds from the present. . In this way, the engine speed N [t] after t seconds is predicted. Similarly, the fuel injection amount Q [t] after t seconds is predicted based on the time change of the fuel injection amount from t seconds before to the present time. FIG. 3 shows an example of changes in the operating state of the engine 1. 3, the point P [−t] indicates the operating state of the engine 1 before t seconds, the point P indicates the current operating state, and the point P [t] indicates the operating state of the engine 1 after t seconds. ing.

  In subsequent step S16, the ECU 20 determines whether or not the predicted operating state of the engine 1 after t seconds is an operating state within the S regeneration operation region of FIG. In other words, it is determined whether or not the position specified in FIG. 3 is within the S regeneration region by the engine speed N [t] after t seconds from the present and the fuel injection amount Q [t] after t seconds from the present. . When it is determined that the predicted operating state of the engine 1 is within the S regeneration operation region, the process proceeds to step S17, where the ECU 20 performs air-fuel ratio rich control, and the air-fuel ratio in the vicinity of the NOx catalyst 8 is richer than the stoichiometric air-fuel ratio. Thus, the fuel is added from the fuel addition valve 10 so that the NO regeneration of the NOx catalyst 8 is performed. If S reproduction is already being executed, the S reproduction is continued. Thereafter, the current control routine is terminated.

  On the other hand, when it is determined that the predicted operating state of the engine 1 is an operating state outside the S regeneration operation region of FIG. 3, the process proceeds to step S18, where the ECU 20 performs normal control and adds fuel from the fuel addition valve 10. Limit and stop S playback. Thereafter, the current control routine is terminated. In this process, fuel addition may be limited so that fuel is not added from the fuel addition valve 10, that is, the amount of added fuel becomes zero. Further, when the operation state of the engine 1 changes to an operation state outside the S regeneration operation region during the S regeneration, an amount of fuel is added so that the temperature of the NOx catalyst 8 can be maintained at the target temperature during the S regeneration. The fuel addition may be limited as described above.

  If a negative determination is made in step S13 or a negative determination is made in step S14, the process proceeds to step S19, where the ECU 20 performs normal control of the injector 30, and the fuel addition valve so that fuel addition from the fuel addition valve 10 is stopped. 10 operations are controlled. Thereafter, the current control routine is terminated.

  In the control routine of FIG. 2, the operation state of the engine 1 after t seconds is predicted, and when the predicted operation state is an operation state in the S regeneration operation region, the S regeneration is performed, and the operation outside the S regeneration operation region is performed. Since the S regeneration is stopped in the state, useless fuel addition can be suppressed. Therefore, the amount of fuel consumed for S regeneration can be reduced.

  The ECU 20 functions as an operating state acquisition unit of the present invention by executing the process of step S11 of FIG. 2, and functions as an operating state predicting unit of the present invention by executing the process of step S15 of FIG. . Moreover, it functions as the operation control means of the present invention by executing the processing of steps S17 and S18 of FIG.

(Second form)
Next, a second embodiment of the exhaust emission control device of the present invention will be described with reference to FIGS. This form is different only in the content of the S regeneration control, and the other configuration is the same as the first form. Accordingly, FIG. 1 is referred to for the engine 1. FIG. 5 is a flowchart showing an S regeneration control routine according to the second embodiment, and FIG. 6 shows an example of a map used in the control routine of FIG.

  First, a method for predicting the operating state of the engine 1 in this embodiment will be described with reference to FIG. FIG. 6 shows an example of the relationship between the rotational speed and fuel injection amount of the engine 1 and the S regeneration operation region as in FIG. 3 of the first embodiment. As shown in FIG. 6, a plurality of determination regions M are set in the S regeneration operation region A so as not to overlap each other, and an average duration T is set in each determination region M. As shown in FIG. 6, each determination area M is identified with a determination area number M [1], M [2],..., M [n]. The numbers in each determination area M in FIG. 6 indicate the average duration T set in each determination area M. The average duration T is assumed to be the start time when the operating state of the engine 1 becomes the operating state of each determination region M, and thereafter the operating state of the engine 1 is expected to be maintained in the operating state within the S regeneration operation region A. Is the average time spent. For example, when the operating state of the engine 1 becomes the operating state of the determination region M [7] in FIG. 6, that is, when the operating state of the engine 1 becomes the point P11 in FIG. It is expected that the operation state in the S regeneration operation area A is maintained for 8 seconds. Therefore, in this case, the operation state of the engine 1 is predicted to be the operation state in the S regeneration operation region until 1.8 seconds later. Therefore, in this case, the operating state of the engine 1 after 2 seconds, which is the minimum rich addition time, can be predicted as an operating state outside the S regeneration operation region. The relationship shown in FIG. 6 as an example is obtained in advance through experiments or the like and stored in the ECU 20 in advance.

  Thus, the ECU 20 predicts the operating state of the engine 1 and repeatedly executes the control routine of FIG. 5 at a predetermined cycle during the operation of the engine 1 in order to control the S regeneration based on the predicted operating state of the engine 1. To do. In FIG. 5, the same processes as those in FIG.

  In the control routine of FIG. 5, the ECU 20 first obtains the rotational speed N and the fuel injection amount Q, which are the current operating state of the engine 1, in step S11. In subsequent step S13, the ECU 20 determines whether or not S regeneration of the NOx catalyst 8 is requested. If it is determined that the S regeneration is requested, the process proceeds to step S14, and the ECU 20 determines whether or not the current operation state of the engine 1 is an operation state within the S regeneration operation region. If it is determined that the current operating state of the engine 1 is an operating state within the S regeneration operation region, the process proceeds to step S21, where the ECU 20 is acquired when the control routine of FIG. The operation state of the engine 1 (hereinafter also referred to as the previous operation state) when this control routine was executed last time using the previous rotation speed Nold and the previous fuel injection amount Qold is the operation in the S regeneration operation region. It is determined whether or not it was in a state. The acquisition of the previous rotation speed Nold and the previous fuel injection amount Qold will be described in step S31 described later. When it is determined that the previous operation state is the operation state in the S regeneration operation region, step S22 is skipped and the process proceeds to step S23. On the other hand, if it is determined that the previous operation state is an operation state outside the S regeneration operation region, the process proceeds to step S22, where the ECU 20 determines a plurality of determination regions M in which the current operation state of the engine 1 is set in the S regeneration operation region A. The start determination area number Ms that is the determination area number of the determination area M is acquired. Determination of the determination area M and acquisition of the determination area number are performed with reference to the map of FIG. The acquired start determination area number Ms is stored in the RAM of the ECU 20 and used when the control routine is executed next time. Thereafter, the process proceeds to step S23.

  In step S23, the ECU 20 determines whether or not the timekeeping flag indicating that the time during which the operation state of the engine 1 is actually maintained in the operation state within the S regeneration operation region is being measured is on. If it is determined that the timekeeping flag is on, steps S24 and S25 are skipped and the process proceeds to step S26. On the other hand, if it is determined that the timekeeping flag is off, the process proceeds to step S24, where the ECU 20 switches the timekeeping flag on. In the next step S25, the ECU 20 sets the timer value for measuring the time during which the operation state of the engine 1 is actually maintained in the operation state within the S regeneration operation region to the initial value 0, and from the initial value to the timer Start counting.

  In the next step S26, the ECU 20 acquires the average duration T based on the current operating state of the engine 1. This average duration T is acquired with reference to the map of FIG. In subsequent step S27, the ECU 20 determines whether or not the acquired average duration T is equal to or longer than the minimum rich addition time. As the lowest rich addition time, for example, 2 seconds is set as in the first embodiment. When it is determined that the average duration T is equal to or longer than the minimum rich addition time, the process proceeds to step S17, where the ECU 20 executes S regeneration of the NOx catalyst 8. Thereafter, the current control routine is terminated. On the other hand, when it is determined that the average duration T is less than the minimum rich addition time, the process proceeds to step S18, and the ECU 20 stops the S regeneration. Thereafter, the current control routine is terminated.

  If a negative determination is made in step S13 or a negative determination is made in step S14, the process proceeds to step S28, and the ECU 20 determines whether or not the timekeeping flag is on. If it is determined that the timekeeping flag is off, steps S29 and S30 are skipped and the process proceeds to step S31. On the other hand, if it is determined that the timekeeping flag is on, the process proceeds to step S29 where the ECU 20 continues the average continuation set in the start determination area number Ms based on the start determination area number Ms stored in the ECU 20 and the current value of the timer. Correct time T. Specifically, for example, when the average duration T set in the start determination area number Ms is 2.0 seconds and the timer value is 2.5 seconds, the average duration T is 2.0 seconds. And a time between 2.5 seconds, for example 2.2 seconds. Note that the correction range when correcting the average duration may be changed according to the number of corrections of the average duration. For example, the correction range is reduced as the number of corrections increases. In the subsequent step S30, the ECU 20 switches the timing flag off.

  In the next step S31, the ECU 20 substitutes the current engine speed 1 for the previous engine speed Nold and the current fuel injection quantity Q for the engine 1 for the previous fuel injection quantity Qold. Note that the previous rotation speed Nold and the previous fuel injection amount Qold are stored in the RAM of the ECU 20 even after the control routine is completed, and are used when the control routine of FIG. 5 is executed next. In the subsequent step S19, the ECU 20 performs normal control of the injector 30 and stops fuel addition from the fuel addition valve 10. Thereafter, the current control routine is terminated.

  In the control routine of FIG. 5, the average duration T that is expected to be maintained in the operating state in the S regeneration operation region is predicted, and the predicted average duration T is equal to or greater than the minimum rich addition time. When the S regeneration is executed and the average duration T is less than the minimum rich addition time, the S regeneration is stopped, so that unnecessary fuel addition can be suppressed. Therefore, the amount of fuel consumed for S regeneration can be reduced.

  Further, the processing of steps S23 to S25 and steps S28 to S30 in FIG. 5 is executed to correct the average duration T set for each determination region M, so that each determination region M and average duration T are The correspondence relationship can be corrected to the correspondence relationship reflecting the operation history of each engine 1. Therefore, the driver's habit or the like is reflected in the correspondence relationship between each determination region M and the average duration time T, and the prediction accuracy of the normal duration time T can be further improved. Therefore, useless fuel addition can be further suppressed, and the amount of fuel consumed for S regeneration can be further reduced.

  In FIG. 6, a plurality of determination regions having substantially the same size are set in the S regeneration operation region, but the size of each determination region may not be the same. Further, the shape of the determination region is not limited to the lattice shape shown in FIG. As long as the plurality of determination areas are set so as not to overlap the S regeneration operation area, the determination areas may be appropriately changed in size and shape to easily reflect the operation history of each engine 1.

  The ECU 20 functions as a storage unit of the present invention by storing the relationship shown in FIG. 6 as a map, and executes the processes of steps S23 to S25 and steps S28 to S30 of FIG. By correcting the correspondence with the duration T, it functions as the learning means of the present invention. Moreover, it functions as the time acquisition means of the present invention by executing the processing of steps S23 to S25 and S28 and S29 in FIG.

  This invention is not limited to each form mentioned above, It can implement with a various form. For example, the present invention is not limited to a diesel engine, and may be applied to various internal combustion engines that use gasoline or other fuels.

  The exhaust gas purification means provided in the exhaust gas purification unit is not limited to the one in which the NOx storage reduction catalyst is supported on the carrier. For example, a filter substrate for collecting particulates may be provided with a storage reduction type NOx catalyst material supported thereon. Further, the exhaust purification catalyst to which the present invention is applied is not limited to the NOx storage reduction catalyst. The present invention is applicable to various exhaust purification catalysts that are regenerative and that have limited engine operating conditions suitable for the regeneration. By applying the present invention to such an exhaust purification catalyst, wasteful regeneration processing can be suppressed.

The figure which shows the internal combustion engine in which the exhaust gas purification apparatus of this invention was integrated. The flowchart which shows the S reproduction | regeneration control routine which concerns on the 1st form of this invention. The figure which shows an example of the relationship between an engine speed and fuel injection quantity, and S reproduction | regeneration driving | operation area | region. The figure which shows an example of the time change of the rotation speed of an engine. The flowchart which shows S reproduction | regeneration control routine which concerns on the 2nd form of this invention. The figure which shows an example of the relationship between an engine speed and the amount of fuel injection, and each determination area | region, and an example of the relationship between each determination area | region and average duration.

Explanation of symbols

1 Internal combustion engine 4 Exhaust passage 8 NOx storage reduction catalyst (exhaust purification catalyst)
10 Fuel addition valve (reducing agent addition means)
20 Engine control unit (operating state acquisition means, catalyst regeneration execution means, operating state prediction means, operation control means, storage means, time acquisition means, learning means)

Claims (5)

A regenerative exhaust purification catalyst provided in an exhaust passage of the internal combustion engine, a reducing agent addition means for adding a reducing agent from an upstream side of the exhaust purification catalyst, an operating state acquisition means for acquiring an operating state of the internal combustion engine, When it is determined that a predetermined regeneration execution condition is satisfied, including that the operating state acquired by the operating state acquisition means is an operating state within a predetermined operating region suitable for the regeneration processing of the exhaust purification catalyst, the reduction In an exhaust gas purification apparatus for an internal combustion engine, comprising: a catalyst regeneration executing means for adding a reducing agent from an agent adding means to execute a regeneration process of the exhaust purification catalyst,
The catalyst regeneration execution means, when the predetermined regeneration execution condition is satisfied, an operation state prediction means for predicting an operation state of the internal combustion engine after a predetermined time has elapsed since the predetermined regeneration execution condition is satisfied. And an operation control means for controlling the operation of the reducing agent adding means based on the operating condition predicted by the operating condition predicting means. When the predetermined regeneration execution condition is satisfied, the operating state predicting means satisfies the predetermined regeneration execution condition based on a history of the operation state of the internal combustion engine up to a point in time when the predetermined regeneration execution condition is satisfied. Predicting the operating state of the internal combustion engine after the predetermined time has elapsed since the time point,
When the operation state predicted by the operation state prediction unit is an operation state outside the predetermined operation region, the operation control unit is configured to limit the addition of the reducing agent from the reducing agent addition unit. 2. An exhaust emission control device for an internal combustion engine according to claim 1, wherein the operation of the adding means is controlled. The operating state predicting means is configured to determine whether the operation state of the plurality of determination regions and the internal combustion engine set so as not to overlap each other in the predetermined operation region and the operation state in each determination region are within the predetermined operation region. Storage means for storing a map that associates a duration time that is expected to be maintained in a state;
When the predetermined regeneration execution condition is satisfied, the operation control means refers to the map to determine whether the operation state of the internal combustion engine at the time when the predetermined regeneration execution condition is satisfied is any of the plurality of determination regions. And the duration is acquired based on the determination result, and the addition of the reducing agent from the reducing agent addition means is limited when the duration is less than the predetermined time. The exhaust gas purification apparatus for an internal combustion engine according to claim 1, wherein the operation of the reducing agent adding means is controlled as described above.   The operating state predicting means is acquired by time acquiring means for acquiring the time during which the operating state of the internal combustion engine is actually maintained in the predetermined operating region from the operating state of each determination region, and acquired by the time acquiring unit. The exhaust emission control device for an internal combustion engine according to claim 3, further comprising learning means for correcting a correspondence relationship between the plurality of determination regions and the duration based on time.   5. The fuel according to claim 1, wherein the exhaust purification catalyst is an NOx storage reduction catalyst, and the fuel for the internal combustion engine is added as a reducing agent from the reducing agent adding means. An exhaust purification device for an internal combustion engine.

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