JP2008157187A - Egr control device for engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an EGR control device for an engine, capable of controlling an exhaust circulation quantity with favorable precision, even with an engine having a particulate filter. <P>SOLUTION: When forced regeneration of the particulate filter 34 is not being executed, correction coefficient Kc to charging efficiency is set in accordance with a result of comparison of exhaust pressure with reference exhaust pressure as exhaust pressure in a reference state where no particulates are accumulated on the particulate filter 34. The charging efficiency determined in accordance with operation states of the engine 1 is corrected by the correction coefficient Kc to determine corrected charging efficiency. Theoretical air feed quantity into the cylinder of the engine 1 is determined based on the corrected charging efficiency, and an EGR valve 26 is controlled based on the theoretical air feed quantity. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an engine EGR control device, and more particularly to an engine EGR control device in which a particulate filter for collecting particulates in exhaust gas is provided in an exhaust passage.

Conventionally, an EGR passage that connects an intake passage and an exhaust passage of an engine is provided, and a part of the exhaust of the engine is recirculated from the EGR passage to the intake side, thereby lowering the combustion temperature in the combustion chamber and excessive engine air. An EGR device is used in which the NOx (nitrogen oxide) emission of the engine is suppressed by reducing the rate.
If the exhaust gas recirculation amount becomes excessive when performing exhaust gas recirculation through the EGR passage, the amount of oxygen in the combustion chamber becomes insufficient and combustion deteriorates. In the case of a diesel engine, the particulates in the exhaust gas increase, Problems such as smoke may occur. Further, when the exhaust gas recirculation amount is insufficient, there arises a problem that NOx emission cannot be sufficiently suppressed.

In order to prevent such a problem, it is necessary to control the EGR valve provided in the EGR passage so as to obtain an appropriate exhaust gas recirculation amount.
When exhaust gas recirculation is performed through the EGR passage, the theoretical air supply amount, which is the amount of gas supplied to each cylinder of the engine, is equal to the amount of fresh air that is air taken into the engine from the atmosphere, and EGR This is the sum of the amount of exhaust gas recirculated through the passage. That is, when the exhaust gas recirculation amount increases under a constant operation state, the fresh air intake amount decreases, and when the exhaust gas recirculation amount decreases, the fresh air intake amount increases.

  Therefore, the theoretical air supply amount of the engine is obtained based on the engine operating state such as the load and the rotational speed, and if the intake amount of fresh air is detected using an air flow meter or the like, the actual exhaust gas recirculation amount at that time is obtained. It becomes possible. Therefore, if the EGR valve is controlled so that the exhaust gas recirculation amount and the excess air ratio become appropriate amounts according to the operating state of the engine based on the theoretical air supply amount and the fresh air intake amount, the above-described problems can be solved. Can be solved.

On the other hand, in a diesel engine or the like, in order to purify the exhaust gas by removing the particulates contained in the exhaust gas, a particulate filter is disposed in the exhaust passage, and the exhaust gas flows into the particulate filter to flow the particulates in the exhaust gas. I try to collect curates.
In this case, the particulates are collected by the particulate filter, and as the particulates accumulate on the particulate filter, the exhaust resistance in the particulate filter increases and the exhaust pressure upstream of the particulate filter increases. . For this reason, even if the engine operating state used to calculate the theoretical air supply amount is the same, the amount of gas actually supplied to each cylinder of the engine decreases as the exhaust pressure increases and is calculated. There will be an error with the theoretical air supply. As a result, there arises a problem that even if the EGR valve is controlled based on such a theoretical air supply amount, an appropriate exhaust gas recirculation amount cannot be obtained.

Therefore, in order to solve such a problem, Patent Document 1 proposes an EGR control device that controls the exhaust gas recirculation amount in consideration of the change in the exhaust pressure due to the accumulation of particulates.
In the EGR control device of Patent Document 1, a reference intake air amount that is an intake air amount of the engine when an appropriate exhaust gas recirculation amount is obtained in a reference state in which no particulates are accumulated on the particulate filter is set to the engine operating state. The EGR valve is controlled so that the actual intake air amount becomes the reference air amount. At this time, the accumulated amount of particulates in the particulate filter is obtained based on the deviation between the reference intake pipe pressure and the actual intake pipe pressure when the intake air amount of the engine is set as the reference intake air amount in the reference state. The reference intake air amount is corrected based on the amount.

By correcting the reference intake air amount in this manner, the error in the reference intake air amount accompanying the accumulation of particulates on the particulate filter is corrected, and the particulates are accumulated on the particulate filter. Also, the exhaust gas recirculation amount can be appropriately controlled.
JP 2001-193522 A

  However, the EGR control device disclosed in Patent Document 1 determines the amount of particulates accumulated in the particulate filter based on the intake pipe pressure. Although the intake pipe pressure fluctuates according to fluctuations in the exhaust pressure accompanying the accumulation of particulates, there is a delay with respect to changes in the exhaust pressure and also fluctuates due to factors other than the exhaust pressure. The amount of deposition cannot be determined. Therefore, there is a problem that the exhaust gas recirculation amount may not be accurately controlled in the EGR control device of Patent Document 1.

  In addition, in the particulate filter, the exhaust resistance gradually increases as the collected particulate matter accumulates in the particulate filter. Therefore, when the particulate accumulation amount reaches a predetermined amount, the temperature of the particulate filter is increased. The exhaust gas purification function of the particulate filter is maintained by forcibly incinerating the particulate filter and forcibly regenerating the particulate filter.

When such forced regeneration is performed, the particulates accumulated on the particulate filter are incinerated and removed, so that the exhaust resistance of the particulate filter rapidly decreases and the exhaust pressure changes suddenly.
However, the EGR control device of Patent Document 1 does not take into account the sudden change in exhaust pressure due to the forced regeneration of the particulate filter, and the reference intake pipe pressure is always set to the actual intake pressure regardless of whether or not the forced regeneration is performed. The reference intake air amount is corrected according to the deviation from the intake pipe pressure. For this reason, in a special engine operating state in which the intake air amount is limited, such as forced regeneration of the particulate filter, the reference intake air amount cannot be properly corrected, and an appropriate exhaust gas recirculation amount cannot be obtained. The problem arises.

  The present invention has been made in view of such problems, and an object of the present invention is to provide an engine EGR control device capable of accurately controlling the exhaust gas recirculation amount even in an engine having a particulate filter. There is to do.

  In order to achieve the above object, an EGR control device for an engine according to the present invention includes a particulate filter that is disposed in an exhaust passage of an engine and collects particulates in exhaust, an intake passage of the engine, and an exhaust passage. An EGR passage communicating with the EGR passage, an EGR valve disposed in the EGR passage, for adjusting a flow rate of exhaust gas recirculated from the exhaust passage to the intake passage through the EGR passage, and an exhaust pressure in the exhaust passage Exhaust pressure detecting means for detecting the operating condition detecting means for detecting the operating condition of the engine, forced regeneration means for forcibly regenerating the particulate filter, and operation of the engine detected by the operating condition detecting means The charging efficiency calculating means for determining the charging efficiency of the engine based on the state, and the particulate filter comprises the particulate Reference pressure calculation means for obtaining the exhaust pressure when the engine is in a reference state that is not deposited as reference exhaust pressure based on the operating state of the engine detected by the operating state detection means, and the particulates by the forced regeneration means The charging efficiency calculating means according to a comparison result between the exhaust pressure detected by the exhaust pressure detecting means and the reference exhaust pressure obtained by the reference pressure calculating means when forced regeneration of the filter is not executed. Correction coefficient setting means for setting a correction coefficient for the filling efficiency obtained by the above, and correction by correcting the filling efficiency obtained by the filling efficiency calculation means with the correction coefficient set by the correction coefficient setting means. A filling efficiency correction means for determining a filling efficiency, and the compensation obtained by the filling efficiency correction means. Based on the charging efficiency, the theoretical air supply amount calculating means for obtaining the theoretical air supply amount supplied into the cylinder of the engine, and the EGR valve based on the theoretical air supply amount determined by the theoretical air supply amount calculating means. EGR control means for controlling is provided (claim 1).

According to the engine EGR control apparatus configured as described above, the charging efficiency of the engine is obtained by the charging efficiency calculation means based on the operating state of the engine, and the particulate filter is brought into a reference state in which no particulates are accumulated. The exhaust pressure at a certain time is obtained as the reference exhaust pressure by the reference pressure calculation means based on the operating state of the engine.
Then, when the forced regeneration of the particulate filter is not executed by the forced regeneration means, the correction coefficient setting means determines the charging efficiency according to the comparison result between the exhaust pressure detected by the exhaust pressure detection means and the reference exhaust pressure. The correction efficiency is set, and the filling efficiency correction means corrects the filling efficiency obtained by the filling efficiency calculation means with the correction coefficient to obtain the corrected filling efficiency. Further, the theoretical air supply amount calculating means obtains the theoretical air supply amount supplied into the cylinder of the engine based on the corrected charging efficiency thus obtained, and the EGR control means calculates the EGR based on the theoretical air supply amount. Control the valve.

  In the EGR control apparatus for the engine, the correction coefficient setting means may be configured to calculate the exhaust pressure detected by the exhaust pressure detection means and the reference pressure calculation when the forced regeneration by the forced regeneration means is not executed. The correction coefficient is repeatedly updated and set according to the comparison result with the reference exhaust pressure obtained by the means, and is set immediately before the forced regeneration is started when the forced regeneration by the forced regeneration means is executed. The correction coefficient is set while the forced regeneration is being executed by gradually increasing the correction coefficient by a predetermined increase amount (claim 2).

According to the engine EGR control device configured as described above, when the forced regeneration of the particulate filter by the forced regeneration means is not being executed, the correction coefficient setting means detects the exhaust pressure detected by the exhaust pressure detection means and the reference The correction coefficient is repeatedly updated and set according to the comparison result with the exhaust pressure.
On the other hand, when the forced regeneration of the particulate filter is executed, the correction coefficient setting means predetermines a correction coefficient set immediately before the forced regeneration is started, among the correction coefficients that have been repeatedly updated and set. The correction coefficient is set while the forced regeneration is being executed by gradually increasing the increase amount.

The correction efficiency obtained in this way is used to correct the filling efficiency obtained by the filling efficiency calculation means to obtain the corrected filling efficiency. The theoretical supply obtained based on the corrected filling efficiency and the engine operating state is obtained. The EGR valve is controlled based on the air volume.
In the engine EGR control device, when the forced regeneration by the forced regeneration means is completed, the correction coefficient setting means sets the correction coefficient to an initial value and then detects the exhaust pressure detection means. The correction coefficient is repeatedly updated and set in accordance with the comparison result between the exhaust pressure and the reference exhaust pressure obtained by the reference pressure calculation means, and the first update value of the correction coefficient after the forced regeneration is finished, The initial value of the correction coefficient when the next forced regeneration by the forced regeneration means is completed (claim 3).

  According to the engine EGR control apparatus configured as described above, the correction coefficient setting means sets the correction coefficient to the initial value when the forced regeneration of the particulate filter is completed, and then compares the exhaust pressure with the reference exhaust pressure. The correction coefficient is repeatedly updated and set according to the result. Then, the first updated value of the correction coefficients that are repeatedly updated at this time is set as the initial value of the correction coefficient when the next forced regeneration is completed.

The engine EGR control device further includes a deterioration determination unit that determines deterioration of the particulate filter based on the magnitude of the correction coefficient set by the correction coefficient setting unit. 4).
According to the engine EGR control device configured as described above, the deterioration determining means determines the deterioration of the particulate filter based on the magnitude of the correction coefficient set by the correction coefficient setting means.

  According to the EGR control apparatus for an engine of the present invention, when the forced regeneration of the particulate filter is not performed by the forced regeneration means, the exhaust pressure when the particulate filter is in a reference state in which no particulate is deposited is obtained. The corrected charging efficiency of the engine is corrected by a correction coefficient set according to the comparison result between a certain reference exhaust pressure and the actual exhaust pressure, and the corrected charging efficiency is obtained. Based on this, the EGR valve is controlled.

Therefore, the EGR valve can be appropriately controlled by correcting the filling efficiency by the correction coefficient without being affected by the forced regeneration of the particulate filter.
In addition, the charging efficiency of the engine is directly affected when the exhaust pressure changes due to the accumulation of particulates on the particulate filter. In this way, the charging efficiency obtained based on the operating state of the engine is used as a reference. By correcting with the correction coefficient obtained according to the comparison result between the exhaust pressure and the actual exhaust pressure amount, it becomes possible to accurately obtain the correction filling efficiency corresponding to the change in the exhaust pressure accompanying the accumulation of particulates. .

As a result, the theoretical air supply amount can be obtained accurately based on the corrected charging efficiency, and an appropriate exhaust gas recirculation amount can be obtained by controlling the EGR valve based on the theoretical air supply amount, so that the exhaust characteristics of the engine can be improved. It can be maintained well.
According to the engine EGR control device of claim 2, when the forced regeneration of the particulate filter is executed, the forced correction among the correction coefficients that have been repeatedly updated and set when the forced regeneration is not executed. The correction coefficient set during the forced regeneration is set by gradually increasing the correction coefficient set immediately before the reproduction is started by a predetermined increase amount.

  Therefore, the correction coefficient can be changed to approximate the change in the exhaust pressure that changes with the forced regeneration of the particulate filter. For example, a standard exhaust pressure during the forced regeneration of the particulate filter can be changed. By grasping the change in advance and setting the amount of increase in the correction coefficient so as to correspond to this change in exhaust pressure, even if forced regeneration is being performed, it is approximately approximate to the actual engine charging efficiency It is possible to obtain the corrected filling efficiency. As a result, even when the forced regeneration is being performed, the theoretical air supply amount can be accurately obtained, and an appropriate exhaust gas recirculation amount can be obtained.

According to the engine EGR control apparatus of claim 3, after the forced regeneration of the particulate filter is completed, the correction coefficient is repeatedly updated and set according to the comparison result between the exhaust pressure and the reference exhaust pressure. Then, the first updated value of the correction coefficients that are repeatedly updated at this time is set as the initial value of the correction coefficient when the next forced regeneration is completed.
The state of the particulate filter immediately after the end of forced regeneration does not always become a constant state, but varies with aging. The updated value of the first correction coefficient after the end of forced regeneration is the most reliable correction coefficient corresponding to the state of the particulate filter immediately after the end of forced regeneration, and the next forced regeneration is executed. By using the initial value of the correction coefficient when the process is completed, the correction filling efficiency can be obtained with higher accuracy than when the constant value is always a constant value. Therefore, an appropriate exhaust gas recirculation amount can be obtained immediately after the forced regeneration of the particulate filter is completed.

  According to the engine EGR control apparatus of the fourth aspect, the deterioration of the particulate filter is determined based on the magnitude of the correction coefficient. The larger the degree of correction by the correction coefficient, the more the state of the particulate filter becomes the reference. Since it is far from the state, it is possible to accurately determine the deterioration of the particulate filter depending on the magnitude of the correction coefficient.

An engine EGR control apparatus according to an embodiment of the present invention will be described below with reference to the drawings.
FIG. 1 shows a system configuration diagram of a four-cylinder diesel engine (hereinafter referred to as an engine) to which an EGR control device according to an embodiment of the present invention is applied. The EGR control device according to the present invention is based on FIG. The structure of will be described.

The engine 1 includes a high pressure accumulator chamber (hereinafter referred to as a common rail) 2 common to each cylinder, and light oil that is high pressure fuel supplied from a fuel injection pump (not shown) and stored in the common rail 2 is provided in each cylinder. The fuel oil is supplied to the injectors 4 and light oil is injected from the injectors 4 into the respective cylinders.
The intake pipe 6 is equipped with a turbocharger 8. The intake air drawn from an air cleaner (not shown) flows into the compressor 8a of the turbocharger 8 from the intake pipe 6, and the intake air supercharged by the compressor 8a is intercooler. 10 and an intake control valve 12 to be introduced into an intake manifold (intake passage) 14.

An intake air amount sensor 16 for detecting the amount of air sucked into the engine 1 from the atmosphere, that is, the amount of fresh air, is provided upstream of the compressor 8a of the intake pipe 6. Between the intake control valve 12 and the intake manifold 14, an intake pressure sensor 18 that detects the intake pressure and an intake temperature sensor 20 that detects the intake air temperature are provided for intake air of the engine 1.
On the other hand, an exhaust port (not shown) through which exhaust is discharged from each cylinder of the engine 1 is connected to an exhaust pipe 24 via an exhaust manifold (exhaust passage) 22. An EGR passage 28 is provided between the exhaust manifold 22 and the intake manifold 14 to connect the exhaust manifold 22 and the intake manifold 14 via the EGR valve 26, and the opening degree of the EGR valve 26 is changed. Thus, the exhaust gas recirculation amount from the exhaust manifold 22 to the intake manifold 14 can be adjusted.

The exhaust pipe 24 is connected to the exhaust aftertreatment device 30 after passing through the turbine 8 b of the turbocharger 8. The rotating shaft of the turbine 8b is connected to the rotating shaft of the compressor 8a so that the turbine 8b receives the exhaust flowing in the exhaust pipe 20 and drives the compressor 8a.
The exhaust after-treatment device 30 contains a NOx storage catalyst 32, and a particulate filter that purifies the exhaust of the engine 1 by collecting particulates in the exhaust downstream of the NOx storage catalyst 32 ( 34) is housed.

The NOx occlusion catalyst 32 occludes NOx in the exhaust gas when the oxygen concentration in the inflowing exhaust gas is high, and a reducing component such as HC or CO in the inflowing exhaust gas has a low oxygen concentration in the exhaust gas. It has a function of releasing and reducing the stored NOx when it is in a reducing atmosphere.
The filter 34 is made of a honeycomb-type ceramic body, and a large number of passages that connect the upstream side and the downstream side are arranged side by side, and the upstream side opening and the downstream side opening of the passage are alternately closed. Particulates in the exhaust are collected as the exhaust flows inside.

NOx in the exhaust gas that has been stored in the NOx storage catalyst 32 after the NOx storage amount exceeds the limit amount flows into the filter 34, and acts as an oxidant on the particulates trapped and accumulated in the filter 34. The particulates are oxidized and removed from the filter 34, and the filter 34 is continuously regenerated and becomes N ₂ and discharged into the atmosphere.
An exhaust temperature sensor 36 for detecting the temperature of the exhaust gas flowing into the filter 34 and an exhaust pressure sensor (exhaust pressure detection means) 38 for detecting the pressure of the exhaust gas flowing into the filter 34 are provided on the upstream side of the filter 34. Yes. An outlet side exhaust pressure sensor 40 that detects the pressure of the exhaust gas flowing out from the filter 34 is provided on the downstream side of the filter 34.

The ECU 42 is a control device for performing comprehensive control including operation control of the engine 1, and includes a CPU, a memory, a timer counter, and the like. The ECU 42 calculates various control amounts and based on the control amounts. Controls various devices.
On the input side of the ECU 42, in order to collect information necessary for various controls, the intake air amount sensor 16, the intake air pressure sensor 18, the intake air temperature sensor 20, the exhaust gas temperature sensor 36, the exhaust gas pressure sensor 38, and the outlet side exhaust gas pressure sensor described above. In addition to 40, various sensors such as an engine speed sensor 44 for detecting the engine speed and an accelerator opening sensor 46 for detecting the amount of depression of an accelerator pedal (not shown) are connected. Various devices such as the injector 4, the intake control valve 12, and the EGR valve 26 of each cylinder to be controlled based on the controlled amount are connected.

  The ECU 42 also calculates the fuel supply amount to each cylinder of the engine 1 and controls the fuel supply from the injector 4 based on the calculated fuel supply amount. The fuel supply amount (main injection amount) necessary for the operation of the engine 1 is stored in advance based on the engine speed detected by the speed sensor 44 and the accelerator pedal depression amount detected by the accelerator opening sensor 46. It is determined by reading from the map. The amount of fuel supplied to each cylinder is adjusted by the valve opening time of the injector 4, and each injector 4 is driven to open in a driving time corresponding to the determined fuel amount, and main injection is performed in each cylinder. Thus, the amount of fuel necessary for the operation of the engine 1 is supplied.

In addition to the fuel supply control to each cylinder, the ECU 42 also performs control for forcibly regenerating the filter 34 to restore its function.
Particulates deposited on the filter 34 are oxidized and removed by continuous regeneration by reaction with NOx flowing into the filter 34 without being occluded by the NOx occlusion catalyst 32 as described above. In such a case, the accumulated particulates may not be sufficiently removed by oxidation only by such continuous regeneration. If such a state continues, particulates excessively accumulate in the filter 34 and the filter 34 may be clogged. Therefore, the filter 34 may be forcibly regenerated as appropriate depending on the particulate accumulation state in the filter 34. Done.

The accumulation state of the particulates is estimated based on the detection values of the exhaust pressure sensor 38, the outlet side exhaust pressure sensor 40 and the intake air amount sensor 16 provided on the upstream side and the downstream side of the filter 34, respectively. When it is determined that the curated deposition amount has reached a predetermined amount, the forced regeneration control is started.
In this forced regeneration control, the intake control valve 12 is controlled in the closing direction based on the temperature of the exhaust gas flowing into the filter 34 detected by the exhaust temperature sensor 36 to raise the exhaust gas temperature, and the injector 4 is retarded from the main injection. The post-injection thus performed is performed in the expansion stroke and exhaust stroke of the engine 1, and the temperature of the filter 34 is raised to a temperature at which the particulates accumulated on the filter 34 can be incinerated. That is, the HC supplied into the exhaust gas by the post injection from the injector 4 reaches the NOx storage catalyst 32, and the high temperature exhaust gas whose temperature has further increased due to the oxidation reaction of HC in the NOx storage catalyst 32 flows into the filter 34. . The particulates deposited on the filter 34 are incinerated by the exhaust gas that has become high in this manner, and the filter 34 is forcibly regenerated. Therefore, in this embodiment, the injector 4 or the intake control valve 12 provided in each cylinder of the engine 1 corresponds to the forced regeneration means of the present invention.

Further, the ECU 42 adjusts the opening degree of the EGR valve 26 provided in the EGR passage 28 and controls the amount of exhaust gas recirculated from the exhaust manifold 22 to the intake manifold 14, thereby setting the excess air ratio of the engine 1 to the target air. Control excess rate.
This target excess air ratio is a control map based on the number of revolutions of the engine 1 and the fuel injection amount by main injection in advance as an excess air ratio that can suppress the generation of NOx without deteriorating the combustion state in each combustion chamber of the engine 1. It is something that is remembered.

In addition to the fresh air amount sucked by the engine 1 detected by the intake air amount sensor 16, the ECU 42 includes the fuel injection amount supplied from the injector 4 to the combustion chamber by the main injection and the exhaust gas recirculated through the EGR passage 28. Based on the amount of air contained, the actual excess air ratio is repeatedly calculated.
At this time, the amount of air contained in the exhaust gas recirculated through the EGR passage 28 is the intake amount of the engine 1 detected by the intake air amount sensor 16 from the theoretical supply amount that is the amount of gas supplied to the combustion chamber of the engine 1. This is obtained based on the exhaust gas recirculation amount obtained by reducing the new air amount and the actual excess air ratio calculated last time.

Further, the theoretical air supply amount used in such calculation is the charging efficiency of the engine 1 determined according to the operating state such as the rotation speed and load of the engine 1, the intake pressure detected by the intake pressure sensor 18, and the intake air pressure. It is obtained based on the intake air temperature detected by the air temperature sensor 20.
The ECU 42 controls the opening degree of the EGR valve 26 so that the actual excess air ratio thus obtained becomes equal to the target excess air ratio.

  Here, a filter 34 is provided on the exhaust side of the engine 1, and the exhaust resistance increases as particulates accumulate on the filter 34, so that the engine 1 has the same rotational speed and load. However, the exhaust pressure will increase with the accumulation of particulates. As the exhaust pressure increases, the charging efficiency of the engine 1 decreases. Therefore, the ECU 42 controls the opening degree of the EGR valve 26 in consideration of the particulate accumulation state in the filter 34.

Hereinafter, control of the EGR valve 26 performed by the ECU 42 will be described in detail with reference to the drawings.
FIG. 2 is a functional configuration diagram of the ECU 42 corresponding to the control of the EGR valve 26 in the present embodiment.
In the ECU 42, based on the number of revolutions of the engine 1 detected by the number of revolutions sensor 44 and the fuel injection amounts by main injection, pilot injection, and post injection calculated in the ECU 42, a charging efficiency calculation unit (charging efficiency calculation means). 48, the filling efficiency of the engine 1 when the filter 34 is in a reference state in which no particulates are accumulated is read out from a previously stored map. Therefore, in the present embodiment, the rotation speed sensor 44 and the ECU 42 correspond to the driving state detection means of the present invention.

  On the other hand, the reference pressure calculation unit (reference pressure calculation means) 50 maps the exhaust pressure upstream of the filter 34 when the filter 34 is in the reference state in advance according to the rotational speed of the engine 1 and the fuel injection amount. The exhaust pressure corresponding to the rotational speed of the engine 1 detected by the rotational speed sensor 44 and the fuel injection amount calculated in the ECU 42 is read out from the map and obtained as a reference exhaust pressure.

The reference exhaust pressure obtained in this way by the reference pressure calculation unit 50 is sent to the correction coefficient setting unit (correction coefficient setting means) 52, and the actual exhaust pressure upstream of the filter 34 detected by the exhaust pressure sensor 38 is detected. Based on the difference from the reference exhaust pressure, a correction coefficient Kc for the charging efficiency determined by the charging efficiency calculation unit 48 is determined.
The method of setting the correction coefficient Kc in the correction coefficient setting unit 52 will be described in detail later. In the state where the filter 34 is not forcibly regenerated, as described above, the filter 34 increases as the amount of accumulated particulates increases. Since the upstream exhaust pressure increases and the charging efficiency of the engine 1 decreases, the larger the difference between the actual exhaust pressure and the reference exhaust pressure, the more the charging efficiency calculated by the charging efficiency calculation means 48. The correction coefficient Kc is set so as to further decrease.

On the other hand, in the state in which the filter 34 is forcibly regenerated, the exhaust pressure on the upstream side of the filter 34 decreases according to the incineration removal of the particulates due to the forced regeneration, and therefore, when the filter 34 is not forcibly regenerated. A correction coefficient Kc is set in a direction in which the charging efficiency corrected in the decreasing direction is restored.
The filling efficiency correction unit (filling efficiency correction means) 54 obtains the correction filling efficiency by multiplying the filling efficiency obtained by the filling efficiency calculation unit 48 and the correction coefficient Kc set by the correction coefficient setting unit 52, Output to the theoretical air supply amount calculation unit (theoretical air supply amount calculation means) 56.

In addition to the corrected charging efficiency obtained by the charging efficiency correction unit 54, the theoretical air supply amount calculation unit 56 includes the rotation speed of the engine 1 detected by the rotation speed sensor 44 and the engine 1 detected by the intake pressure sensor 18. The intake pressure and the intake air temperature of the engine 1 detected by the intake air temperature sensor 20 are input.
Based on these inputs, the theoretical air supply amount calculation unit 56 obtains the theoretical air supply amount as the amount of gas supplied into each cylinder of the engine 1 per unit time. That is, the exhaust gas recirculation amount via the EGR passage 28 is calculated from the air density obtained from the intake pressure and intake air temperature of the engine 1, the stroke volume of the engine 1 stored in advance, and the corrected charging efficiency determined by the charging efficiency correction unit 54. The theoretical air supply amount is obtained as the amount of gas supplied to the engine 1 including

The theoretical air supply amount obtained in this way is output to an EGR control unit (EGR control means) 58, and the EGR control unit 58 detects the intake air amount of the engine 1 detected by the theoretical air supply amount and the intake air amount sensor 16. The opening degree of the EGR control valve 26 is controlled based on the air volume.
That is, the theoretical air supply amount obtained by the theoretical air supply amount calculation unit 56 is the amount of fresh air sucked into the engine 1 and the amount of exhaust gas recirculated from the exhaust manifold 28 to the intake manifold 14 via the EGR passage 26. Therefore, the exhaust gas recirculation amount can be obtained by subtracting the intake fresh air amount of the engine 1 detected by the intake air amount sensor 16 from the theoretical intake air amount.

Further, the EGR control unit 58 is recirculated through the intake air amount detected by the intake air amount sensor 16, the fuel injection amount supplied from the injector 4 to the combustion chamber by the main injection and the like, and the EGR passage 28. The actual excess air ratio of the engine 1 is repeatedly calculated based on the amount of air contained in the exhaust gas.
At this time, the amount of air contained in the exhaust gas recirculated through the EGR passage 28 is obtained based on the exhaust gas recirculation amount obtained as described above and the actual excess air ratio calculated last time.

  Further, the EGR control unit 58 sets the target excess air ratio as the excess air ratio that can appropriately suppress the generation of NOx without deteriorating the combustion state in each combustion chamber of the engine 1, the target excess air ratio, the engine speed, the main injection, and the like. Is stored in advance as a map on the basis of the fuel injection amount by the engine, and the target charging corresponding to the fuel injection amount such as the main injection obtained in the ECU 42 and the rotational speed of the engine 1 detected by the rotational speed sensor 44 is stored. The efficiency is read from the map and set.

Then, the EGR control unit 58 controls the opening degree of the EGR valve 26 so that the actual excess air ratio obtained as described above becomes equal to the target excess air ratio read and set from the map.
By controlling the opening degree of the EGR valve 26 in this way, the excess air ratio of the engine 1 can appropriately suppress the generation of NOx without deteriorating the combustion state in each combustion chamber of the engine 1. The exhaust performance of the engine 1 can be maintained satisfactorily.

  Further, in the calculation of the theoretical air supply amount that is used when determining the actual excess air ratio, the engine 1 of the engine 1 is based on the deviation between the exhaust pressure that changes in accordance with the particulate accumulation state on the filter 34 and the reference exhaust pressure. Since the filling efficiency is corrected, the exhaust pressure increases as the exhaust pressure increases with the accumulation of particulates on the filter 34, or the exhaust pressure decreases rapidly due to the forced regeneration of the filter 34. Even in this case, the theoretical air supply amount can be obtained with high accuracy, and the excess air ratio of the engine 1 can be properly maintained.

Hereinafter, details of the setting control of the correction coefficient Kc performed by the correction coefficient setting unit 52 will be described with reference to the drawings.
FIG. 3 is a flowchart of the correction coefficient setting control performed by the correction coefficient setting unit 52 in the present embodiment.
The correction coefficient setting control is started at the start of the engine 1 and is repeatedly executed at a predetermined control period according to the flowchart of FIG. 3 until the engine 1 is stopped.

When the engine 1 is started and correction coefficient setting control is started, it is determined in step S1 whether or not forced regeneration of the filter 34 is being executed.
Here, if it is the first control period after the engine 1 is started and the forced regeneration of the filter 34 is not executed, the process proceeds to step S2 by the determination of step S1, and whether or not the value of the flag F1 is 1 or not. Determine whether. The flag F1 indicates that it is the first control cycle after the forced regeneration of the filter 34 is ended when the value is 0, and the initial value is 0.

Accordingly, if it is determined in step S2 that the value of the flag F1 is 0, the process proceeds to step S3, where the value of the flag F1 is set to 1, and in the next step S4, the value of the flag F2 described later is reset to 0, and then In step S5, a counter value Nd described later is reset to zero.
In the next step S6, the initial value of the correction coefficient Kc is set to the value of the correction coefficient Kc stored in the previous control cycle. In the case of the first control cycle when the engine 1 is started, the previous control cycle is Since it does not exist, the value of the correction coefficient Kc stored when the engine 1 was operating last time is used. That is, when the engine 1 was operating last time, the correction coefficient Kc obtained immediately before the engine 1 was stopped is stored when the engine 1 is stopped, and is used as the initial value of the correction coefficient Kc in this step S6.

The correction coefficient Kc having the initial value set in this way is used for the correction of the charging efficiency by the charging efficiency correction unit 54. In the correction coefficient setting control, the current control cycle is terminated and step S1 is performed again in the next control cycle. Start processing from.
If the forced regeneration of the filter 34 is not continuously performed in the next control cycle, the process proceeds from step S1 to step S2, but since the value of the flag F1 is 1 in the first control cycle, Then, unless the value of the flag F1 is reset to 0 again, the process proceeds from step S2 to step S7 every control cycle.

In step S7, it is determined whether or not the engine 1 is in a steady operation state. Specifically, based on the rate of change of the rotational speed of the engine 1 detected by the rotational speed sensor 44 and the rate of change of the fuel injection amount such as the main injection set by the ECU 42, the rate of change is predetermined. When the value is smaller than the determination value, it is determined that the engine 1 is in a steady operation state.
If it is determined in step S7 that the engine 1 is in a steady operation state, the process proceeds to step S8, and it is determined whether the exhaust gas recirculation is stopped by fully closing the EGR valve 26.

  If it is determined in step S7 that the engine 1 is not in a steady operation state, or if it is determined in step S8 that exhaust gas recirculation is not stopped, then the control cycle is terminated without doing anything, and the next The process starts again from step S1 in the control cycle. That is, when the engine 1 is not in a steady operation state or when exhaust gas recirculation is being performed, the correction coefficient cannot be calculated with high accuracy, and thus the control cycle ends without calculating the correction coefficient in this way. I am doing so.

On the other hand, if it is determined in step S8 that exhaust gas recirculation is stopped, the process proceeds to step S9, the actual exhaust pressure upstream of the filter 34 detected by the exhaust pressure sensor 36 is taken in, and the process proceeds to the next step S10. .
In step S10, the actual exhaust pressure taken in in step S9 and the exhaust pressure upstream of the filter 34 when the filter 34 is in the reference state where particulates are not accumulated are as described above in the reference pressure calculation unit 50. The obtained reference exhaust pressure is compared, and a temporary correction coefficient Km is read from a previously stored map and set based on the deviation between the actual exhaust pressure and the reference exhaust pressure.

This temporary correction coefficient Km map obtains the charging efficiency of the engine 1 that changes in accordance with the change of the exhaust pressure in advance through experiments or the like, and shows the ratio between the charging efficiency thus obtained and the charging efficiency at the reference exhaust pressure. Based on this, the temporary correction coefficient Km is stored corresponding to the deviation between the actual exhaust pressure and the reference exhaust pressure.
Further, in step S10, the temporary correction coefficient Km obtained in this way is stored, and the temporary correction coefficient Km repeatedly obtained in the same manner in each control cycle and subsequent times is sequentially integrated to obtain an integrated value ΣKm.

Next, when the process proceeds to step S11, 1 is added to the counter value Nd to obtain a new counter value Nd.
Since the counter value Nd is reset to 0 in the first control cycle as described above, 1 is added every time the process proceeds to step S11 unless the counter value Nd is reset thereafter. The value Nd indicates the number of temporary correction coefficients Km accumulated in step S10.

In the next step S12, it is determined whether or not the counter value Nd has reached n. That is, it is determined whether or not the number of provisional correction coefficients Km accumulated in step S10 has reached n. If the counter value Nd is not yet n, the control cycle is ended, and the process is started again from step S1 in the next control cycle.
The integration of the counter value Nd in step S10 is repeated every control cycle, and when the n temporary correction coefficients Km are integrated and the counter value Nd becomes n, the process proceeds to step S13, and the integration of the n temporary correction coefficients Km is performed. By dividing the value ΣKm by n, a correction coefficient Kc used to correct the charging efficiency in the charging efficiency correction unit 54 is obtained. Then, the correction coefficient Kc that has been used in the charging efficiency correction unit 54 until then is replaced with the correction coefficient Kc thus obtained.

In the next step S14, it is determined whether or not the value of the flag F2 is zero. This flag F2 indicates that the value of 0 indicates that the calculation of the correction coefficient Kc performed in step S13 is the first calculation after the forced regeneration of the filter 34 is completed.
Since the flag F2 has not been changed since the value was reset to 0 in step S4 in the control cycle when it was determined in step S2 that the value of the flag F1 was 0 as described above, It is determined that the value of the flag F2 is 0, and the process proceeds to step S15.

In step S15, the correction coefficient Kc obtained in step S13 is stored. The correction coefficient Kc stored here is used in step S6 described above as the initial value of the correction coefficient Kc after the forced regeneration is completed when the forced regeneration of the filter 34 is executed again.
Next, when the process proceeds to step S16, the value of the flag F2 is set to 1, the control cycle is ended, and the process is started again from step S1 in the next control cycle.

If the forced regeneration of the filter 34 is not executed after the next control cycle, the value of the flag F1 remains 1, so that the engine 1 is in a steady operation state and the exhaust gas recirculation is stopped. The process of step S9 thru | or step S12 is repeated for every control period.
Then, whenever the number of provisional correction coefficients Km accumulated in step S10 becomes n, the process proceeds to step S13, and the correction coefficient Kc is obtained as an average value of the integrated values ΣKm of the n provisional correction coefficients Km.

Further, when the process proceeds from step S13 to step S14, it is determined whether or not the value of the flag F2 is 0. Since the value of the flag F2 has already been set to 1 in step S16 as described above, In S14, it is determined that the value of the flag F2 is not 0, and the control cycle ends.
As described above, when the forced regeneration of the filter 34 is not executed and the engine 1 is in a steady operation state and the exhaust gas recirculation is stopped, the deviation between the reference exhaust pressure and the actual exhaust pressure every control cycle. The temporary correction coefficients Km obtained according to the above are integrated, and the correction coefficient Kc is obtained as an average value of the n temporary correction coefficients Km every time the number of integrated temporary correction coefficients Km reaches n. The obtained correction coefficient Kc is used by the charging efficiency correction unit 54 to correct the charging efficiency.

  The correction coefficient Kc set here is an average value of the n temporary correction coefficients Km. The temporary correction coefficient Km is, as described above, the charging efficiency of the engine 1 that changes in accordance with the change in the exhaust pressure. Based on the ratio of the charging efficiency at the reference exhaust pressure when the filter 34 is in the reference state, it is stored in advance in the map, and the deviation between the actual exhaust pressure upstream of the filter 34 and the reference exhaust pressure is calculated. Accordingly, it is obtained from this map.

  Therefore, by correcting the filling efficiency of the engine 1 when the filter 34 obtained by the filling efficiency calculation unit 48 is in the reference state by multiplying by the correction coefficient Kc, a corrected filling efficiency that substantially matches the actual filling factor is obtained. be able to. For this reason, the theoretical air supply amount calculation unit 56 can obtain the theoretical air supply amount with high accuracy, and as a result, the exhaust gas recirculation amount can be accurately controlled to maintain the good exhaust characteristics of the engine 1. .

Further, since n temporary correction coefficients Km are integrated and the average value is used as the correction coefficient Kc, an appropriate correction coefficient Kc can be obtained with high accuracy, and when the engine 1 is not in a steady operation state or exhaust gas recirculation is performed. If so, the calculation of the temporary correction coefficient Km is not performed, and the accuracy of the correction coefficient Kc can be kept high.
When particulates accumulate on the filter 34 and forced regeneration of the filter 34 is executed, it is determined in step S1 that the filter 34 is being forcedly regenerated, and the process proceeds to step S17.

  In step S17, the value of the flag F1 is reset to 0, and in the next step S18, the coefficient Kramp that gradually increases with the passage of time after the start of forced regeneration of the filter 34 is added to the correction coefficient Kc set in the previous control cycle. By multiplying, the correction coefficient Kc of the control cycle is set, and the control cycle is completed. Therefore, in the first control period after the forced regeneration of the filter 34 is started, the correction coefficient Kc obtained in step S13 immediately before the forced regeneration of the filter 34 is multiplied by the coefficient Kramp to correct the control period. A coefficient Kc is obtained.

The filling efficiency correction unit 54 multiplies the filling efficiency obtained by the filling love rate calculation unit 48 by the correction coefficient Kc set in this way to correct the filling efficiency to obtain the corrected filling efficiency.
The coefficient Kramp used here grasps in advance a standard change in the exhaust pressure upstream of the filter 34 when the filter 34 is forcibly regenerated by experiments or the like, and responds to this change in the exhaust pressure. The value that changes is stored in the map.

Assuming that the forced regeneration of the filter 34 is continuously executed in the next control cycle, the process again proceeds from step S1 to step S17 to step S18, and the coefficient Kramp is added to the correction coefficient Kc set in step S18 of the previous control cycle. And a correction coefficient Kc for the control period is set.
Therefore, while the forced regeneration of the filter 34 is being executed, the correction coefficient Kc is gradually increased by an increase amount corresponding to the coefficient Kramp, with the correction coefficient Kc set immediately before the start of the forced regeneration of the filter 34 being an initial value. The correction coefficient Kc is used by the charging efficiency correction unit 54 to correct the charging efficiency.

  As described above, the coefficient Kramp is stored in advance based on the standard change in the exhaust pressure upstream of the filter 34 when the filter 34 is forcibly regenerated. By setting the correction coefficient Kc using Kramp, it is possible to change the correction coefficient Kc in response to a change in the exhaust pressure upstream of the filter 34 that changes relatively rapidly as the filter 34 is forcedly regenerated. Become.

  Therefore, even when the filter 34 is being forcibly regenerated, the charging efficiency correction unit 54 can obtain a correction charging efficiency that is approximately approximate to the actual charging efficiency of the engine 1. The theoretical air supply amount can be obtained with high accuracy. As a result, even when the filter 34 is being forcibly regenerated, an appropriate exhaust gas recirculation amount can be secured and the exhaust characteristics of the engine 1 can be maintained well.

When the particulates of the filter 34 are incinerated and removed by forced regeneration and the forced regeneration of the filter 34 is completed, it is determined in step S1 that the forced regeneration of the filter 34 has not been executed, and the process proceeds to step S2.
In step S2, it is determined whether or not the value of the flag F1 is 0. However, since the value of the flag F1 is reset to 0 in step S18 when the forced regeneration of the filter 34 is being executed, the processing is performed in step S2. Proceed to S3.

In step S3, the value of the flag F1 is set to 1. In subsequent steps S4 and S5, the value of the flag F2 is reset to 0 and the counter value Nd is reset to 0.
In the next step S6, the correction coefficient Kc stored in step S15 before the forced regeneration of the filter 34 that was executed immediately before is set as the correction coefficient Kc of the control period, and the control period ends. . That is, after the previous forced regeneration of the filter 34 is completed, the correction coefficient Kc first obtained in step S13 is stored in step S15, and in step S6, this correction coefficient Kc is the forced regeneration of the current filter 34. Used as the initial value of the correction coefficient Kc immediately after the end.

  Immediately after the forced regeneration of the filter 34, particulates are not substantially accumulated on the filter 34. However, the exhaust pressure upstream of the filter 34 does not necessarily recover to the reference exhaust pressure due to the aging of the filter 34. . For this reason, if the same value is always used as the initial value of the correction coefficient Kc immediately after the forced regeneration of the filter 34, the value of the correct correction coefficient Kc immediately after the forced regeneration of the filter 34 is changed due to the aging of the filter 34. Deviation occurs.

  Therefore, in this embodiment, the updated value of the correction coefficient Kc obtained in step S13 after the forced regeneration of the filter 34 is finished is set as the initial value of the correction coefficient Kc when the forced regeneration of the next filter 34 is finished. The updated value of the correction coefficient Kc that is first obtained after the forced regeneration of the filter 34 is the most reliable correction coefficient Kc at that time corresponding to the state of the filter 34 immediately after the forced regeneration is completed. By using the coefficient Kc, it is possible to obtain a highly accurate filling efficiency considering the secular change of the filter 34. As a result, an appropriate exhaust gas recirculation amount can be obtained immediately after the forced regeneration of the filter 34 is completed.

If the forced regeneration of the filter 34 is not executed even in the next control cycle, the process proceeds from step S1 to step S2 to determine whether or not the value of the flag F1 is 0. Since it is set to 1 in step S3 in the control cycle, the process proceeds from step S2 to step S7.
Accordingly, when the forced regeneration of the filter 34 is completed, the correction coefficient Kc is set to the initial value as described above in the control period immediately after that, and then the engine 1 is in a steady operation state in the subsequent control period and the exhaust gas recirculation. As long as the engine is stopped, the provisional correction coefficient Km obtained according to the deviation between the reference exhaust pressure and the actual exhaust pressure is integrated every control cycle as described above, and the integrated provisional correction coefficient Km When the number reaches n, the correction coefficient Kc is obtained as an average value of the n temporary correction coefficients Km, and the correction coefficient Kc thus obtained is used by the filling efficiency correction unit 54 to correct the filling efficiency.

After the forced regeneration of the filter 34 is completed, the correction coefficient Kc first obtained in step S13 is stored in step S15, and is used as an initial value of the correction coefficient Kc when the forced regeneration of the next filter 34 is completed. Used.
An example of the change in the correction coefficient Kc when the correction coefficient setting control is executed as described above is shown in FIG.

  The correction coefficient Kc is used to correct the filling efficiency obtained by the filling efficiency calculation unit 48, and the filling efficiency obtained by the filling efficiency calculation unit 48 is in a reference state where the particulate matter is not accumulated in the filter 34. This is the charging efficiency of the engine 1 at a certain time. As particulates accumulate on the filter 34, the exhaust pressure on the upstream side of the filter 34 increases and the charging efficiency decreases. Therefore, the correction coefficient Kc set when the filter 34 is not forcibly regenerated. This corrects the filling efficiency obtained by the filling efficiency calculation unit 48 in the decreasing direction.

Therefore, the correction coefficient Kc has a positive value of 1 or less, and the correction coefficient Kc gradually decreases as the exhaust pressure on the upstream side of the filter 34 increases with the accumulation of particulates on the filter 34. It is set to the direction to do.
If the forced regeneration of the filter 34 is not executed until time t1 in FIG. 4, every time n temporary correction coefficients Km are integrated by the processing in steps S9 to S13 in FIG. 3 described above until time t1. Since the correction coefficient Kc is updated and set, the correction coefficient Kc gradually decreases.

When the forced regeneration of the filter 34 is started at time t1, the correction coefficient Kc is set in step S18 in FIG. 3, so that during the forced regeneration of the filter 34, the correction set immediately before the forced regeneration is started. Using the coefficient Kc as an initial value, the correction coefficient Kc gradually increases with an increase corresponding to the coefficient Kramp as described above.
When the forced regeneration of the filter 34 ends at time t2, the correction coefficient Kc first obtained in step S13 in FIG. 3 after the forced regeneration one time before the forced regeneration that has been performed is terminated. Use the initial value. Thereafter, the n temporary correction coefficients Km are integrated, and when the average value of the integrated values ΣKm is obtained at time t 3, the correction coefficient Kc is updated with this average value, and this average value is then converted to the filter 34. Stored as the initial value of the correction coefficient Kc after the forced regeneration is executed.

Thereafter, until the forced regeneration of the filter 34 is started at time t4, the correction coefficient Kc is updated each time n temporary correction coefficients Km are accumulated, and the particulates to the filter 34 are updated. As the exhaust pressure on the upstream side of the filter 34 increases with the accumulation, the correction coefficient Kc increases stepwise.
When the forced regeneration of the filter 34 is started at time t4, as described above, the correction coefficient Kc set immediately before the start of forced regeneration is used as an initial value until the forced regeneration of the filter 34 ends at time t5. The correction coefficient Kc gradually increases by an increase amount corresponding to the coefficient Kramp.

  When the forced regeneration of the filter 34 is completed at time t5, the correction coefficient Kc first obtained from the integrated value ΣKm of the n temporary correction coefficients Km and stored after time t3 is used as the initial value of the correction coefficient Kc. Is set. Thereafter, the correction coefficient Kc is updated every time the n temporary correction coefficients Km are integrated as described above, and the exhaust pressure upstream of the filter 34 is increased with the accumulation of particulates on the filter 34. As the value increases, the correction coefficient Kc increases stepwise.

  By setting the correction coefficient Kc as described above, when the filter 34 is not forcibly regenerated, the exhaust pressure on the upstream side of the filter 34 that rises as particulates accumulate on the filter 34 is increased. A correction coefficient Kc is set corresponding to the deviation from the reference exhaust pressure, and the charging efficiency of the engine 1 corresponding to the reference exhaust pressure is corrected by this correction coefficient Kc, so that the correction is almost equal to the actual charging efficiency of the engine 1. It is possible to determine the filling efficiency.

For this reason, it is possible to accurately obtain the theoretical air supply amount, and as a result, it is possible to accurately control the exhaust gas recirculation amount and maintain good exhaust characteristics of the engine 1.
In addition, when the filter 34 is forcibly regenerated, the correction coefficient Kc is set so as to gradually increase using the coefficient Kramp, so that the filter 34 changes relatively rapidly as the filter 34 is forcibly regenerated. It is possible to change the correction coefficient Kc corresponding to the change in the upstream exhaust pressure.

Therefore, even when the filter 34 is being forcibly regenerated, it is possible to obtain a corrected charging efficiency that is approximately approximate to the actual charging efficiency of the engine 1, and to obtain the theoretical air supply amount with high accuracy. As a result, even when the filter 34 is being forcibly regenerated, an appropriate exhaust gas recirculation amount can be secured and the exhaust characteristics of the engine 1 can be maintained well.
Further, since the updated value of the correction coefficient Kc that is first obtained after the forced regeneration of the filter 34 is set as the initial value of the correction coefficient Kc after the next forced regeneration is completed, the filter 34 is considered in consideration of the secular change of the filter 34. An appropriate exhaust gas recirculation amount can be obtained immediately after the forced regeneration is completed.

  Note that the updated value of the correction coefficient Kc that is first obtained after the forced regeneration of the filter 34 in this way reflects the aging of the filter 34, and the exhaust pressure on the upstream side of the filter 34 as the filter 34 deteriorates. As the value increases, it gradually changes to a smaller value. Therefore, the ECU 42 determines that the filter 34 has deteriorated when the updated value of the correction coefficient Kc obtained first after the forced regeneration of the filter 34 falls below a preset determination value, and prompts replacement of the filter 34. Display is done. Therefore, the ECU 42 corresponds to the deterioration determination means of the present invention.

By determining the deterioration of the filter 34 in this manner, it is possible to appropriately determine the deterioration accompanying the secular change of the filter 34.
This is the end of the description of the engine EGR control device according to one embodiment of the present invention, but the present invention is not limited to the above embodiment.
For example, in the above embodiment, when the filter 34 is not forcibly regenerated, the difference between the actual exhaust pressure taken in step S9 in FIG. 3 and the reference exhaust pressure obtained by the reference pressure calculation unit 50 is determined. The temporary correction coefficient Km is integrated n times, and the average value is set as the correction coefficient Kc. The actual exhaust pressure is taken in n times in step S9, and the map is based on the deviation between the average value and the reference exhaust pressure. The correction coefficient Kc may be obtained directly.

Further, the correction coefficient Kc may be used as it is without accumulating n temporary correction coefficients Km. However, in this case, the accuracy of the correction coefficient Kc is somewhat lowered.
Further, in the above embodiment, when the forced regeneration of the filter 34 is being executed, the correction coefficient Kc is gradually increased linearly by the multiplication of the coefficient Kramp, but the exhaust pressure upstream of the filter 34 accompanying the forced regeneration of the filter 34 is increased. According to the decrease form, the form of gradually increasing the correction coefficient Kc can be changed as appropriate. That is, the reduction form of the exhaust pressure on the upstream side of the filter 34 due to the forced regeneration of the filter 34 is grasped in advance by experiments or the like, and the correction coefficient Kc is gradually increased in a quadratic curve so as to approximate this change form. Another function may be set, and the correction coefficient Kc may be gradually increased according to the function.

In the above embodiment, the charging efficiency of the engine 1 calculated by the charging efficiency calculation unit 48 is multiplied by the correction coefficient Kc set by the correction coefficient setting unit 52 to determine the correction charging efficiency. The method of correcting the charging efficiency by the correction coefficient Kc is not limited to this, and any method may be used as long as the charging efficiency is corrected as in the above embodiment.
Further, in the above embodiment, the actual excess air ratio of the engine 1 is obtained from the theoretical supply air amount obtained by the theoretical air supply amount calculating section 56, and the EGR valve 26 is set so that this excess air ratio becomes the target excess air ratio. However, the control of the EGR valve 26 based on the theoretical air supply amount is not limited to this. For example, the control is simplified, and the actual exhaust gas recirculation amount is obtained by subtracting the fresh intake air amount of the engine 1 detected by the intake air amount sensor 16 from the theoretical air supply amount so that the exhaust gas recirculation amount becomes the target exhaust gas recirculation amount. Alternatively, the EGR valve 26 may be controlled.

  In the above embodiment, the engine 1 is a four-cylinder diesel engine. However, the engine 1 is provided with a filter 34 that collects particulates in the exhaust gas in the exhaust passage and performs exhaust gas recirculation through the EGR passage 28. Any format can be used.

1 is an overall configuration diagram of an engine to which an EGR control device according to an embodiment of the present invention is applied. It is a functional block diagram corresponding to the control performed by the EGR control apparatus of FIG. It is a flowchart of the correction coefficient setting control performed with the EGR control apparatus of FIG. 3 is a time chart showing an example of a temporal change of a correction coefficient set by correction coefficient setting control performed by the EGR control device of FIG. 1.

Explanation of symbols

1 Engine 4 Injector (Forced regeneration means)
14 Intake manifold (intake passage)
22 Exhaust manifold (exhaust passage)
26 EGR valve 28 EGR passage 34 Particulate filter 42 ECU (operating state detecting means, deterioration determining means)
44 Rotational speed sensor (Operating state detection means)
48 Filling efficiency calculation unit (filling efficiency calculation means)
50 Reference pressure calculator (reference pressure calculator)
52 Correction coefficient setting section (Correction coefficient setting means)
54. Filling efficiency correction unit (filling efficiency correction means)
56 Theoretical supply amount calculation unit (theoretical supply amount calculation means)
58 EGR control unit (EGR control means)

Claims (4)

A particulate filter that is disposed in the exhaust passage of the engine and collects particulates in the exhaust;
An EGR passage communicating the intake passage of the engine and the exhaust passage;
An EGR valve that is disposed in the EGR passage and adjusts a flow rate of exhaust gas recirculated from the exhaust passage to the intake passage through the EGR passage;
Exhaust pressure detecting means for detecting the exhaust pressure in the exhaust passage;
An operating state detecting means for detecting the operating state of the engine;
Forced regeneration means for performing forced regeneration of the particulate filter;
A charging efficiency calculating means for determining a charging efficiency of the engine based on the operating state of the engine detected by the operating state detecting means;
A reference pressure calculating means for obtaining the exhaust pressure when the particulate filter is in a reference state in which no particulates are accumulated as a reference exhaust pressure based on the operating state of the engine detected by the operating state detecting means;
Comparison result between the exhaust pressure detected by the exhaust pressure detecting means and the reference exhaust pressure obtained by the reference pressure calculating means when the forced regeneration of the particulate filter is not executed by the forced regeneration means And a correction coefficient setting means for setting a correction coefficient for the filling efficiency obtained by the filling efficiency calculation means,
Filling efficiency correction means for correcting the filling efficiency obtained by the filling efficiency calculation means with the correction coefficient set by the correction coefficient setting means to obtain a corrected filling efficiency;
A theoretical air supply amount calculating means for determining a theoretical air supply amount supplied into the cylinder of the engine based on the corrected charging efficiency obtained by the charging efficiency correcting means;
An EGR control device for an engine, comprising: EGR control means for controlling the EGR valve based on the theoretical air supply amount obtained by the theoretical air supply amount calculating means.   When the forced regeneration by the forced regeneration means is not executed, the correction coefficient setting means calculates the exhaust pressure detected by the exhaust pressure detecting means and the reference exhaust pressure obtained by the reference pressure calculating means. The correction coefficient is repeatedly updated and set according to the comparison result, and when the forced regeneration by the forced regeneration means is executed, the correction coefficient set immediately before the forced regeneration is started is increased by a predetermined amount. 2. The engine EGR control device according to claim 1, wherein the correction coefficient is set while the forced regeneration is being executed by gradually increasing the amount.   When the forced regeneration by the forced regeneration means ends, the correction coefficient setting means sets the correction coefficient to an initial value, and then uses the exhaust pressure detected by the exhaust pressure detection means and the reference pressure computing means. The correction coefficient is repeatedly updated and set according to the result of comparison with the obtained reference exhaust pressure, and the first update value of the correction coefficient after the forced regeneration ends is set to the next forced regeneration by the forced regeneration means. The engine EGR control device according to claim 1, wherein the correction value is set to an initial value of the correction coefficient when the processing is finished.   The engine according to any one of claims 1 to 3, further comprising a deterioration determination unit that determines deterioration of the particulate filter based on the magnitude of the correction coefficient set by the correction coefficient setting unit. EGR control device.

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