JP2012026289A - Exhaust emission control device for internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an exhaust emission control device for an engine that can suppress emission and improve fuel consumption by optimizing the regeneration timing of a DPF.SOLUTION: The exhaust emission control device for an engine 1 includes: a normal regeneration control part that regenerates a DPF 32 by controlling the temperature of the DPF 32 to be raised to a prescribed temperature when a PM capturing amount reaches the maximum PM capturing amount or above in prescribed conditions; a normal regeneration efficiency calculating part 41 that calculates regeneration efficiency during a normal regeneration control, executed by the normal regeneration control part, on the basis of the maximum PM capturing amount and the past average temperature of the DPF 32; a current regeneration efficiency calculating part 43 that calculates the regeneration efficiency when regenerating the DPF 32 by temporarily controlling the temperature of the current DPF 32 to be raised to the prescribed temperature on the basis of the current PM capturing amount and the current temperature of the DPF 32; and an early regeneration control part that executes regeneration by controlling the temperature of the DPF 32 to be raised to the prescribed temperature when the calculated current regeneration efficiency is higher than the calculated normal regeneration efficiency.

Description

  The present invention relates to an exhaust emission control device for an internal combustion engine. More specifically, the present invention relates to an exhaust gas purification apparatus for an internal combustion engine provided with an exhaust gas purification filter that captures particulate matter in exhaust gas discharged from the internal combustion engine.

  In an internal combustion engine mounted on an automobile or the like, particularly a compression ignition type internal combustion engine, a large amount of particulate matter is contained in the exhaust gas discharged. This particulate matter is harmful to the human body and is subject to emissions regulations. For this reason, an exhaust purification filter (hereinafter also referred to as “filter”) for removing particulate matter is provided in the exhaust passage of the internal combustion engine.

  In the filter, when a large amount of particulate matter accumulates, a differential pressure is generated between the upstream side and the downstream side of the filter, resulting in a decrease in output and a deterioration in fuel consumption. For this reason, when the particulate matter has accumulated to some extent, it is necessary to burn and remove the deposited particulate matter and regenerate the filter.

  Here, in order to burn and remove the trapped particulate matter, it is necessary to raise the temperature of the filter to about 600 ° C. or higher. Usually, since the temperature of the exhaust gas of the internal combustion engine is about 200 ° C., for example, an oxidation catalyst is provided on the upstream side of the filter and a fuel component is introduced into the exhaust passage by post injection or the like. According to this technique, the temperature of the downstream filter can be raised by the reaction heat accompanying the oxidation reaction that proceeds by the introduction of the fuel component.

  By the way, conventionally, on the condition that the internal combustion engine is warmed up and the oxidation catalyst is activated, based on the trapped amount of particulate matter calculated from the differential pressure between the upstream side and the downstream side of the filter, etc. The filter regeneration time was determined. Specifically, the particulate matter trapped in the filter has a characteristic of being efficiently burned and removed when it exceeds a predetermined amount, so that when the calculated trapped amount exceeds the predetermined amount, the filter is regenerated. Was running.

  However, when the internal combustion engine is in an idle operation state or a low load operation state, the exhaust temperature may decrease, the temperature of the oxidation catalyst may be lower than the activation temperature, and the oxidation catalyst may be in an inactive state. At this time, when the filter is regenerated and the fuel component is introduced into the exhaust passage, the introduced fuel component is discharged without being oxidized, so that there is a problem that the emission deteriorates. Further, since it is necessary to raise the temperature from a low temperature lower than the activation temperature to a high temperature of about 600 ° C. necessary for the combustion removal of the particulate matter, there is a problem that a large amount of fuel is consumed and fuel consumption is deteriorated. It was.

  On the other hand, for example, during the temperature increase control for activating the oxidation catalyst normally performed at the start of the internal combustion engine, during the high load operation, or during the rich operation performed for NOx reduction, the oxidation catalyst is at a high temperature. The filter was not regenerated when the trapped amount of the particulate matter did not exceed a predetermined amount despite being activated in the state. That is, when determining the regeneration time of the filter, the influence on the emission performance and the fuel consumption is not sufficiently considered, and it cannot be said that efficient regeneration is performed.

  Regarding filter regeneration efficiency, for example, Patent Document 1 discloses an exhaust purification device including filter regeneration efficiency calculation means for calculating filter regeneration efficiency. However, the regeneration efficiency referred to in Patent Document 1 is used for determining the deterioration of the oxidation catalyst, and is merely an index as to whether or not the oxidation catalyst normally exhibits an oxidation function.

JP-A-2005-201251

  The present invention has been made in view of the above, and an object of the present invention is to provide an exhaust gas purification apparatus for an internal combustion engine that can suppress emission and improve fuel efficiency by optimizing the regeneration timing of the filter.

  In order to achieve the above object, the present invention provides an exhaust purification filter (for example, an exhaust purification filter (for example, an exhaust pipe 4 described later)) of an internal combustion engine (for example, an engine 1 described later) that captures particulate matter in the exhaust. An exhaust gas purification apparatus for an internal combustion engine provided with a DPF 32) described later is provided. This exhaust purification device sets the exhaust purification filter to a predetermined temperature (for example, 600 ° C.) when the trapped amount of particulate matter becomes equal to or greater than a predetermined trap amount (for example, a maximum PM trap amount described later) under predetermined conditions. Normal regeneration control means (for example, a later-described normal regeneration control unit, ECU 40, means related to execution of step S9 in FIG. 6), the predetermined trapping amount, and the past average temperature of the exhaust purification filter Based on the above, the normal regeneration efficiency calculating means for calculating the regeneration efficiency at the time of the normal regeneration control by the normal regeneration control means (for example, the normal regeneration efficiency calculating section 41, ECU 40 described later, execution of step S4 in FIG. 6) Means), the current amount of trapped particulate matter, and the current temperature of the exhaust gas purification filter. Current reproduction efficiency calculation means for calculating the reproduction efficiency (for example, a current reproduction efficiency calculation unit 43, ECU 40 described later, means for executing step S5 in FIG. 6), and the calculated current reproduction efficiency is calculated. If the regeneration efficiency is higher than the normal regeneration efficiency, early regeneration control means (for example, an early regeneration control unit, ECU 40, which will be described later, step S6 in FIG. 6) performs regeneration by raising the temperature of the exhaust purification filter to the predetermined temperature. And means for executing S7).

In the present invention, regeneration during normal regeneration control is performed based on a predetermined trapped amount of particulate matter, which serves as an index for determining whether to perform regeneration of the exhaust purification filter, and a past average temperature of the exhaust purification filter. The efficiency is calculated, and the regeneration efficiency when the current exhaust purification filter is regenerated is calculated based on the current particulate matter trapping amount of the exhaust purification filter and the current temperature. In addition, when the calculated current regeneration efficiency is higher than the calculated normal regeneration efficiency, the exhaust purification filter is regenerated earlier than usual.
As a result, for example, the temperature of the oxidation catalyst during high temperature operation for early activation of the oxidation catalyst normally performed at the start of the internal combustion engine, high load operation, or rich operation performed for NOx reduction is high. When the regeneration efficiency calculated based on the trapped amount of particulate matter and the temperature of the exhaust purification filter at that time is higher than the regeneration efficiency during normal regeneration control, Can be executed. That is, since the regeneration timing is determined based not only on the trapped amount of particulate matter but also on the temperature of the exhaust purification filter, from the viewpoint of fuel consumption accompanying temperature increase control during regeneration rather than performing normal regeneration. , Can perform efficient regeneration and improve fuel efficiency. In addition, if regeneration efficiency is higher than that during normal regeneration control, regeneration is performed at an early stage.As a result, the frequency of normal regeneration control is reduced. Although the oxidation catalyst is in an inactive state during operation, it is possible to prevent the emission from being deteriorated by performing regeneration.

  In this case, it is preferable that the current regeneration efficiency calculating unit calculates the current regeneration efficiency according to a deviation between the current temperature of the exhaust gas purification filter and the predetermined temperature.

  In the present invention, the current regeneration efficiency is calculated according to the deviation between the current temperature of the exhaust purification filter and a predetermined temperature set during regeneration control. Thereby, said effect is show | played more reliably.

  According to the present invention, it is possible to provide an exhaust gas purification apparatus for an internal combustion engine that can optimize the regeneration timing of the filter and suppress emission and improve fuel efficiency.

It is a figure showing composition of an exhaust-air-purification device of an internal-combustion engine concerning one embodiment of the present invention. It is a figure which shows the structure of the reproduction | regeneration efficiency calculation part of the said embodiment, (A) is a figure which shows the structure of a normal reproduction | regeneration efficiency calculation part, (B) is a figure which shows the structure of the present reproduction | regeneration efficiency calculation part. It is a figure for demonstrating normal reproduction | regeneration control. It is a figure for demonstrating the temperature increase control for the early activation of the oxidation catalyst normally performed at the time of engine starting. It is a figure for demonstrating the reproduction | regeneration control which concerns on the said embodiment. It is a flowchart which shows the procedure of the reproduction | regeneration control which concerns on the said embodiment.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
FIG. 1 is a diagram showing a configuration of an exhaust emission control device for an internal combustion engine according to an embodiment of the present invention. An internal combustion engine (hereinafter referred to as an engine) 1 is a diesel engine that directly injects fuel into a combustion chamber of each cylinder 7, and each cylinder 7 is provided with a fuel injection valve (not shown). These fuel injection valves are electrically connected by an electronic control unit (hereinafter referred to as “ECU”) 40, and the valve opening time and valve closing time of the fuel injection valve are controlled by the ECU 40.

  The engine 1 includes an intake pipe 2 through which intake air flows, an exhaust pipe 4 through which exhaust flows, an EGR passage 6 that recirculates part of the exhaust to the intake side, and a supercharger 8 that pumps intake air to the intake pipe 2. And are provided.

  The intake pipe 2 is connected to the intake port of each cylinder 7 of the engine 1 through a plurality of branch portions of the intake manifold 3. The exhaust pipe 4 is connected to the exhaust port of each cylinder 7 of the engine 1 through a plurality of branch portions of the exhaust manifold 5.

  The supercharger 8 includes a turbine 81 provided in the exhaust pipe 4 and a compressor 82 provided in the intake pipe 2. The turbine 81 is driven by the kinetic energy of the exhaust flowing through the exhaust pipe 4. The compressor 82 is driven by the rotation of the turbine 81 to pressurize the intake air and pump it into the intake pipe 2. The turbine 81 includes a plurality of variable vanes (not shown), and is configured to change the rotational speed of the turbine by changing the opening of the variable vanes. The vane opening degree is electromagnetically controlled by the ECU 40.

  A throttle valve 9 for controlling the intake air amount of the engine 1 is provided on the upstream side of the supercharger 8 in the intake pipe 2. The throttle valve 9 is connected to the ECU 40 via an actuator, and the opening degree is electromagnetically controlled by the ECU 40. The intake air amount controlled by the throttle valve 9 is detected by the air flow meter 21.

  The EGR passage 6 connects the exhaust manifold 5 and the intake manifold 3 to return a part of the exhaust upstream of the turbine 81 to the downstream of the compressor 82 in the intake pipe 2. The EGR passage 6 is provided with an EGR valve 11 that controls the flow rate of the recirculated exhaust gas. The EGR valve 11 is connected to the ECU 40 via an actuator (not shown), and the valve opening degree is electromagnetically controlled by the ECU 40.

  Further, in the exhaust pipe 4, an oxidation catalyst (hereinafter referred to as “DOC”) 31, a DPF (Diesel Particulate Filter) 32, and a NOx trapping reduction catalyst (hereinafter referred to as “LNC”) 33 are disposed upstream of the turbine 81. They are provided in this order from the side.

  A temperature sensor 25 for detecting the temperature of the exhaust is provided between the DOC 31 and the DPF 32 described later in the exhaust pipe 4. The temperature sensor 25 is connected to an ECU 40 described later, and a detection signal thereof is supplied to the ECU 40.

The DOC 31 oxidizes the fuel component introduced into the exhaust by post injection, and raises the temperature of the exhaust with the generated heat, thereby raising the temperature of the downstream DPF 32. As the DOC31, for example, platinum (Pt) acting as a catalyst is supported on an alumina (Al ₂ O ₃ ) carrier, zeolite having excellent HC adsorption action, and excellent steam reforming action of HC. Those composed of rhodium (Rh) are preferably used.

The DPF 32 captures particulate matter (Particulate Matter, hereinafter referred to as “PM”) by depositing it on the surface of the filter and in the pores of the filter as the exhaust passes through the pores of the filter. For example, a wall flow type DPF using a honeycomb structure made of a ceramic porous body such as silicon carbide (SiC) is used.
Note that, in the DPF 32, the pressure loss of the exhaust pipe 4 increases as PM is captured, so that a regeneration process, which will be described later, is performed to burn and remove the captured PM.

  A differential pressure sensor 22 connected via a pressure introduction pipe 23 is provided in the exhaust pipe 4 upstream and downstream of the DPF 32. The differential pressure sensor 22 detects a differential pressure between the upstream pressure and the downstream pressure of the DPF 32. The differential pressure sensor 22 is connected to an ECU 40 described later, and a detection signal thereof is supplied to the ECU 40.

The LNC 33 captures NOx in an oxidizing atmosphere in which the reducing agent (HC and CO) concentration in the exhaust is lower than the oxygen concentration, while the captured NOx is reduced in the reducing atmosphere in which the reducing agent concentration in the exhaust is higher than the oxygen concentration. To reduce and purify.
As the LNC 33, for example, a material composed of a noble metal such as platinum and a NOx adsorbent such as zeolite containing at least one of an alkali metal, an alkaline earth metal, and a rare earth is preferably used.

  When the LNC 33 captures NOx up to the limit of the NOx trapping capacity, that is, the maximum NOx trapping amount, the LNC 33 cannot trap NOx any more. For this reason, exhaust enrichment is performed in order to desorb and purify NOx in a timely manner. Specifically, the enrichment operation is performed in which the air-fuel ratio of the air-fuel mixture combusted in the engine 1 is set to the stoichiometric or richer side than the stoichiometric.

  The ECU 40 shapes an input signal waveform from various sensors, corrects a voltage level to a predetermined level, converts an analog signal value into a digital signal value, and a central processing unit (hereinafter, referred to as a central processing unit). CPU). In addition, the ECU 40 includes a storage circuit that stores various calculation programs and calculation results executed by the CPU, and an output circuit that outputs a control signal to the fuel injection valve, the throttle valve 9 and the like of the engine 1.

  With the hardware configuration described above, the ECU 40 includes the normal playback control unit, the playback efficiency calculation unit including the normal playback efficiency calculation unit 41 and the current playback efficiency calculation unit 43, and the early playback control unit. The

  When the engine 1 is warmed up and the temperature of the DOC 31 becomes equal to or higher than the activation temperature, and the DOC 31 is activated, the normal regeneration control unit determines that the DPF 32 Is regenerated by controlling the temperature to a predetermined temperature (600 ° C.). Specifically, the fuel component is introduced into the DOC 31 by outputting a control signal to the fuel injection valve of the engine 1 and executing post injection. As a result, the DPF 32 is heated by the reaction heat accompanying the oxidation reaction that proceeds in the DOC 31, and regeneration is performed.

Since the temperature of the DOC 31 is highly correlated with the temperature of the exhaust detected by the temperature sensor 25, the temperature of the DOC 31 is estimated by searching a preset DOC 31 temperature table according to the temperature of the exhaust detected by the temperature sensor 25. The
Moreover, the activation temperature of DOC31 is an intrinsic value determined by the composition of DOC31.

The PM trapping amount is calculated by searching a preset PM trapping amount table according to the differential pressure between the upstream pressure and the downstream pressure of the DPF 32 detected by the differential pressure sensor 22. The PM trapping amount table is set so that the PM trapping amount increases as the differential pressure increases.
Further, the predetermined trapping amount is an amount that is set by conducting an experiment in advance and that allows the trapped PM to be burned and removed efficiently. In the present embodiment, the maximum amount of PM trapped by the DPF 32 is set.

FIG. 2 is a diagram showing the configuration of the reproduction efficiency calculation unit, where (A) shows the normal reproduction efficiency calculation unit 41 and (B) shows the current reproduction efficiency calculation unit 43.
The normal regeneration efficiency calculation unit 41 calculates the regeneration efficiency during normal regeneration control by the normal regeneration control unit based on the predetermined capture amount (maximum PM capture amount) and the past average temperature of the DPF 32. As shown in FIG. 2A, the normal regeneration efficiency calculation unit 41 includes a first calculator 411, a second calculator 412, and a multiplier 413.

  The first calculator 411 calculates a regeneration efficiency coefficient according to the trapping amount in accordance with the maximum PM trapping amount that can be trapped by the DPF 32. Here, since the maximum PM trap amount is a fixed value in the DPF 32, the coefficient of regeneration efficiency by the trap amount calculated by the first calculator 411 is a value unique to the DPF 32.

The second computing unit 412 searches the coefficient table for regeneration efficiency by preset temperature rise according to the deviation between the set temperature of the DPF 32 during regeneration control and the past average temperature of the DPF 32, thereby increasing the temperature rise. The coefficient of the reproduction efficiency by is calculated. This coefficient table is set such that the smaller the deviation, the larger the coefficient.
In the present embodiment, the set temperature of the DPF 32 at the time of regeneration control is set to 600 ° C., and the temperature of the DPF 32 estimated during the past control cycle is used to calculate the past average temperature of the DPF 32. .

  The multiplier 413 multiplies the coefficient of the regeneration efficiency by the amount of capture calculated by the first calculator 411 and the coefficient of the regeneration efficiency by the temperature increase calculated by the second calculator 412 to thereby increase the normal regeneration efficiency. calculate.

  The current regeneration efficiency calculation unit 43 calculates the regeneration efficiency when the current DPF 32 is regenerated, based on the current amount of PM captured and the current temperature of the DPF 32. As shown in FIG. 2B, the current reproduction efficiency calculation unit 43 includes a first calculator 431, a second calculator 432, and a multiplier 433.

The first calculator 431 calculates a coefficient of regeneration efficiency based on the capture amount by searching a coefficient table of regeneration efficiency based on a preset capture amount according to the current PM capture amount of the DPF 32. This coefficient table is set so that the coefficient increases as the PM trapping amount increases.
Further, as described above, the current PM trap amount is searched in a preset PM trap amount table according to the differential pressure between the upstream pressure and the downstream pressure of the DPF 32 detected by the differential pressure sensor 22. Is calculated.

The second arithmetic unit 432 searches for a coefficient table of regeneration efficiency by preset temperature rise according to the deviation between the set temperature of the DPF 32 at the time of regeneration control and the current temperature of the DPF 32, thereby increasing the temperature. Calculate the coefficient of playback efficiency. This coefficient table is set such that the smaller the deviation, the larger the coefficient.
Since the current temperature of the DOC 32 is highly correlated with the temperature of the exhaust detected by the temperature sensor 25, by searching a preset DPF 32 temperature table according to the temperature of the exhaust detected by the temperature sensor 25. Presumed.
Further, the set temperature of the DPF 32 at the time of regeneration control is set to 600 ° C. in the present embodiment.

  The multiplier 433 multiplies the coefficient of the regeneration efficiency by the amount of capture calculated by the first calculator 431 by the coefficient of the regeneration efficiency by the temperature increase calculated by the second calculator 432, thereby reducing the current regeneration efficiency. calculate.

  The early playback control unit plays the DPF 32 when the current playback efficiency calculated by the current playback efficiency calculation unit 43 is higher than the normal playback efficiency calculated by the normal playback efficiency calculation unit 41. Execute. Specifically, the fuel component is introduced into the DOC 31 by outputting a control signal to the fuel injection valve of the engine 1 and executing post injection. As a result, the DPF 32 is heated by the reaction heat accompanying the oxidation reaction that proceeds in the DOC 31, and regeneration is performed.

Next, normal reproduction control by the normal reproduction control unit and early reproduction control by the early reproduction control unit will be described with reference to FIGS.
FIG. 3 is a diagram showing the relationship between the fuel consumption during normal regeneration control and the temperatures of the DOC 31 and the DPF 32. As shown in FIG. 3, during normal travel before regeneration, both the DOC 31 and the DPF 32 are in a low temperature state. In normal regeneration control, even if the DPF 32 is in such a low temperature state, regeneration is executed when the trapped amount of PM becomes equal to or greater than a predetermined trap amount (maximum PM trap amount).

  When regeneration is executed by post-injection, the temperature of the DOC 31 starts to rise first, and the temperature of the DPF 32 also starts to rise after a delay. At this time, the post injection amount is controlled to increase as the temperature of the DOC 31 increases. Thereafter, when the temperature of the DPF 32 reaches the set temperature (600 ° C.), the post-injection amount is held at a constant amount, whereby the temperature of the DPF 32 is held near the set temperature.

  Therefore, the fuel consumption by post-injection is represented by the total amount of consumption during temperature rise and consumption during regeneration, and the total amount of fuel is consumed during the regeneration period of the DPF 32. . Further, FIG. 3 suggests that if the regeneration is executed when the temperatures of the DOC 31 and the DPF 32 before regeneration are in a high temperature state, the amount of fuel consumed during the temperature rise can be reduced.

  By the way, when the engine 1 is started, normally, temperature increase control for early activation of the DOC 31 is executed. FIG. 4 is a diagram illustrating the relationship between the fuel consumption during the temperature increase control and the temperatures of the DOC 31 and the DPF 32. As shown in FIG. 4, the temperature of the DOC 31 starts to rise immediately after the start, and the temperature of the DPF 32 also starts to rise with a delay due to the temperature rise control for early activation of the DOC 31. Thereafter, when the temperature of the DOC 31 reaches a certain temperature (for example, 500 ° C.), the temperature increase control is terminated. From FIG. 4, when the engine 1 is started, the DOC 31 and the DPF 32 are in a considerably high temperature state due to the temperature increase control for early activation of the DOC 31. If regeneration is performed in this state, the fuel consumption is greatly increased. It is suggested that it can be reduced.

  Therefore, the early regeneration control according to the present embodiment is executed when the DOC 31 and the DPF 32 are in a high temperature state by the temperature raising control for early activation of the DOC 31 performed at the time of starting. FIG. 5 is a diagram showing the relationship between the fuel consumption during the early regeneration control and the temperatures of the DOC 31 and the DPF 32. As shown in FIG. 5, before the early regeneration control, since the DOC 31 and the DPF 32 are already in a high temperature state of about 500 ° C., the DPF 32 can be raised in a short time to the set temperature (600 ° C.) of the DPF 32 at the time of regeneration, The amount of fuel consumed during the temperature rise is greatly reduced. Therefore, in the early regeneration control according to the present embodiment, the amount of fuel consumed during the regeneration period of the DPF 32 is greatly reduced.

Next, regeneration control of the DPF 32 according to the present embodiment will be described with reference to FIG.
FIG. 6 is a flowchart showing a procedure for regeneration control of the DPF 32 according to the present embodiment. This regeneration control is started and repeated by the ECU 40 when the engine 1 is started.

  In step S1, the temperature of the DPF 32 is estimated. Specifically, the temperature of the DPF 32 is estimated by searching a preset DPF 32 temperature table according to the exhaust gas temperature detected by the temperature sensor 25. Thereafter, the process proceeds to step S2.

  In step S2, the past average temperature of the DPF 32 is calculated. Specifically, the past average temperature of the DPF 32 is calculated using the temperature of the DPF 32 estimated in step S1 and the temperature of the DPF 32 estimated in the past control cycle. Thereafter, the process proceeds to step S3.

  In step S3, the PM trapping amount is estimated. Specifically, it is estimated by searching a preset PM trapping amount table according to the differential pressure between the upstream pressure and the downstream pressure of the DPF 32 detected by the differential pressure sensor 22. Thereafter, the process proceeds to step S4.

  In step S4, the normal reproduction efficiency is calculated. Specifically, as described in detail in the description of the normal regeneration efficiency calculation unit 41, based on the past average temperature of the DPF 32 calculated in step S2 and the maximum PM trapping amount, the regeneration efficiency during normal regeneration control ( Normal playback efficiency) is calculated. Thereafter, the process proceeds to step S5.

  In step S5, the current regeneration efficiency is calculated. Specifically, as described in detail in the description of the current regeneration efficiency calculation unit 43, the temperature of the DPF 32 (current temperature) estimated in step S1 and the estimation in step S3 are performed. Based on the obtained PM trap amount (current PM trap amount), the regeneration efficiency (current regeneration efficiency) when the current DPF 32 is regenerated is calculated. Thereafter, the process proceeds to step S6.

  In step S6, it is determined whether or not the current reproduction efficiency calculated in step S5 is higher than the normal reproduction efficiency calculated in step S4. If this determination is YES, it is determined that it is more efficient to perform regeneration early, and the process proceeds to step S7 to perform early regeneration control of the DPF 32. On the other hand, if this determination is NO, it is determined that it is more efficient to perform normal regeneration control, and the process proceeds to step S8.

  In step S7, early regeneration control of the DPF 32 is executed. Specifically, post injection is performed to introduce a fuel component into the DOC 31, and the DPF 32 is heated and regenerated by reaction heat generated by causing the DOC 31 to proceed with an oxidation reaction. Thereby, the regeneration control of the DPF 32 according to the present embodiment is finished.

In step S8, it is determined whether there is a request for normal playback control. If this determination is YES, the routine proceeds to step S9 where normal regeneration control of the DPF 32 is executed. On the other hand, if this determination is NO, the process returns to step S1.
Whether or not there is a request for normal regeneration control is that there is a request for normal regeneration control when the PM trap amount estimated in step S3 is equal to or greater than the maximum PM trap amount of the DPF 32 on the condition that the DOC 31 is activated. Is done.

  In step S9, normal regeneration control of the DPF 32 is executed. Specifically, post injection is performed to introduce a fuel component into the DOC 31, and the DPF 32 is heated and regenerated by reaction heat generated by causing the DOC 31 to proceed with an oxidation reaction. Thereby, the regeneration control of the DPF 32 according to the present embodiment is finished.

According to this embodiment, the following effects are produced.
In the present embodiment, regeneration during normal regeneration control is performed based on a predetermined capture amount of PM (maximum PM capture amount) that serves as an index for determining whether or not regeneration of the DPF 32 is to be performed and a past average temperature of the DPF 32. The efficiency is calculated, and the regeneration efficiency when the current DPF 32 is regenerated is calculated based on the current PM trapping amount of the DPF 32 and the current temperature. Further, when the calculated current regeneration efficiency is higher than the calculated normal regeneration efficiency, the DPF 32 is regenerated earlier than usual.
Thereby, for example, it is performed at the time of temperature increase control for early activation of the DOC 31 normally performed when the engine 1 is started, at the time of high load operation (such as at the time of high supercharging operation), or for the reduction of NOx in the LNC 33. When the DOC 31 is activated in a high temperature state, such as during rich operation, and the regeneration efficiency calculated based on the trapped amount of PM and the temperature of the DPF 32 is higher than the regeneration efficiency during normal regeneration control In addition, playback can be executed. That is, since the regeneration timing is determined based not only on the trapped amount of PM but also on the temperature of the DPF 32, it is more efficient from the viewpoint of fuel consumption accompanying the temperature increase control during regeneration, rather than performing normal regeneration. Regeneration can be executed and fuel consumption can be improved. In addition, if the regeneration efficiency is higher than that during normal regeneration control, regeneration is performed at an early stage. As a result, the frequency of normal regeneration control is reduced. For example, as in the prior art, the engine 1 is in idle operation or has a low load. Although the DOC 31 is in an inactive state during operation, it is possible to prevent the emission from being deteriorated by executing regeneration.

  In the present embodiment, the current regeneration efficiency is calculated according to the deviation between the current temperature of the DPF 32 and the set temperature of the DPF 32 during regeneration control. Thereby, said effect is show | played more reliably.

It should be noted that the present invention is not limited to the above-described embodiment, and modifications and improvements within the scope that can achieve the object of the present invention are included in the present invention.
For example, in the above-described embodiment, the DOC 31 and the post injection are used as the temperature raising means during the regeneration control of the DPF 32. However, the present invention is not limited to this. For example, a temperature raising means such as a heater may be employed.

1. Engine (internal combustion engine)
22 ... Differential pressure sensor 25 ... Temperature sensor 31 ... DOC
32 ... DPF (exhaust gas purification filter)
33 ... LNC
40 ... ECU (normal regeneration control means, normal regeneration efficiency calculating means, current regeneration efficiency calculating means, early regeneration control means)

Claims (2)

An exhaust purification device for an internal combustion engine comprising an exhaust purification filter that is provided in an exhaust passage of the internal combustion engine and captures particulate matter in the exhaust,
Normal regeneration control means for regenerating the exhaust purification filter by raising the temperature to a predetermined temperature when the trapped amount of the particulate matter is equal to or greater than the predetermined trap amount under a predetermined condition;
Normal regeneration efficiency calculating means for calculating regeneration efficiency during normal regeneration control by the normal regeneration control means based on the predetermined trapping amount and the past average temperature of the exhaust purification filter;
Based on the current trapped amount of particulate matter and the current temperature of the exhaust purification filter, the current regeneration efficiency for calculating the regeneration efficiency when the current exhaust purification filter is temperature-controlled and regenerated to the predetermined temperature A calculation means;
Early regeneration control means for performing regeneration by raising the temperature of the exhaust gas purification filter to the predetermined temperature when the calculated current regeneration efficiency is higher than the calculated normal regeneration efficiency. An exhaust gas purification apparatus for an internal combustion engine characterized by the above. 2. The exhaust gas purification apparatus for an internal combustion engine according to claim 1, wherein the current regeneration efficiency calculating means calculates a current regeneration efficiency in accordance with a deviation between the current temperature of the exhaust gas purification filter and the predetermined temperature. .

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