JP2007327480A - Exhaust emission control system of internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To restrain an increase in a discharge quantity of unburnt fuel and even misfiring, while restraining a discharge quantity of NOx, when an operation state of an internal combustion engine becomes a transitional operation state, in an exhaust emission control system of the internal combustion engine having a supercharger and an EGR device. <P>SOLUTION: Target supercharging pressure and a target EGR gas quantity are calculated on the basis of the operation state of the internal combustion engine (S102). When actual supercharging pressure does not reach the target supercharging pressure when the operation state of the internal combustion engine becomes the transitional operation state (S104), an EGR gas quantity is controlled in a quantity less than the target EGR gas quantity (S106 and S107). <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an exhaust gas purification system for an internal combustion engine including a supercharger and an EGR device.

  As an exhaust gas purification system for an internal combustion engine, one having an EGR device that introduces at least part of the exhaust gas of the internal combustion engine into the intake system as EGR gas is known. By introducing the EGR gas into the intake system, the amount of NOx emission can be reduced.

Patent Document 1 discloses a technique for limiting the amount of change when changing the amount of EGR gas introduced into an intake system in an exhaust gas purification system for an internal combustion engine equipped with an EGR device.
JP-A-5-263716

  In an exhaust gas purification system for an internal combustion engine equipped with a supercharger and an EGR device, the supercharging pressure and the EGR gas amount are changed according to the operating state of the internal combustion engine. However, the responsiveness when changing the supercharging pressure is lower than the responsiveness when changing the EGR gas amount.

  Therefore, when the operation state of the internal combustion engine becomes a transient operation state and the boost pressure is increased and the EGR gas amount is increased, the EGR gas amount is excessively larger than the actual boost pressure. There is. In such a case, the amount of EGR gas is excessively larger than the amount of intake air flowing into the cylinder, which may cause an increase in the discharge amount of unburned fuel and misfire.

  The present invention has been made in view of the above problem, and in an exhaust gas purification system for an internal combustion engine equipped with a supercharger and an EGR device, when the operation state of the internal combustion engine becomes a transient operation state, NOx is reduced. It aims at providing the technique which can also suppress the increase in the discharge amount of unburned fuel, and misfire while suppressing discharge amount.

  In the present invention, the target boost pressure and the target EGR gas amount are calculated based on the operating state of the internal combustion engine. If the actual supercharging pressure does not reach the target supercharging pressure when the operating state of the internal combustion engine becomes a transient operating state, the EGR gas amount is controlled to an amount smaller than the target EGR gas amount.

More specifically, the exhaust gas purification system for an internal combustion engine according to the present invention is:
An EGR device that introduces at least part of the exhaust gas of the internal combustion engine into the intake system of the internal combustion engine as EGR gas;
A supercharger that supercharges intake air using the energy of the exhaust gas of the internal combustion engine;
EGR gas amount control means for controlling the amount of EGR gas introduced into the intake system of the internal combustion engine by the EGR device;
A target EGR gas amount calculating means for calculating a target EGR gas amount which is a target value of the EGR gas amount based on an operating state of the internal combustion engine;
A target boost pressure calculating means for calculating a target boost pressure which is a target value of the boost pressure based on the operating state of the internal combustion engine;
A supercharging pressure detecting means for detecting the actual supercharging pressure,
When the actual supercharging pressure detected by the supercharging pressure detecting means is lower than the target supercharging pressure when the operating state of the internal combustion engine is in a transient operating state, the EGR gas amount control means Is controlled to an amount smaller than the target EGR gas amount.

  According to the present invention, when the operating state of the internal combustion engine is a transient operating state, the amount of EGR gas introduced into the intake system is excessively large with respect to the actual boost pressure (that is, with respect to the intake air amount). The amount can be suppressed. Therefore, when the operation state of the internal combustion engine becomes a transient operation state, it is possible to suppress an increase in the amount of unburned fuel emission and misfire while suppressing the amount of NOx emission.

  In the present invention, when the actual supercharging pressure is lower than the target supercharging pressure when the operating state of the internal combustion engine is a transient operating state, the EGR gas amount is reduced to a smaller amount as the actual supercharging pressure is lower. You may control. Thereby, the amount of EGR gas can be set to an amount more suitable for the actual supercharging pressure.

  In the present invention, when the fuel injection valve in the internal combustion engine directly injects the fuel into the cylinder, the fuel injection valve performs a secondary injection at a time before the main fuel injection performed at a time near the top dead center of the compression stroke. Sub fuel injection execution means for executing fuel injection, sub fuel injection timing control means for controlling the execution timing of sub fuel injection by the sub fuel injection execution means, and target sub fuel that is a target value for the execution timing of sub fuel injection Target auxiliary fuel injection timing calculating means for calculating the injection timing based on the operating state of the internal combustion engine may be further included.

  When the actual supercharging pressure detected by the supercharging pressure detection means is lower than the target supercharging pressure when the operating state of the internal combustion engine is a transient operation state, the auxiliary fuel injection timing control means performs auxiliary fuel injection. May be delayed from the target auxiliary fuel injection timing.

  When the execution timing of the auxiliary fuel injection is retarded, the interval between the execution timing of the auxiliary fuel injection and the execution timing of the main fuel injection is shortened. Therefore, the fuel injected by the auxiliary fuel injection is easily used for combustion.

  Therefore, according to the above, even when the actual supercharging pressure is lower than the target supercharging pressure while the sub fuel injection is being performed, the increase in the amount of unburned fuel and misfire are suppressed. I can do it.

  Here, the lower the supercharging pressure, the smaller the intake air amount. Therefore, the fuel injected by the auxiliary fuel injection is less likely to be used for combustion as the supercharging pressure is lower.

  Therefore, in the above, when the execution timing of the auxiliary fuel injection is delayed from the target auxiliary fuel injection timing, the execution timing of the auxiliary fuel injection may be controlled to be later as the actual supercharging pressure is lower. Thereby, the fuel injected by the auxiliary fuel injection can be made easier to burn.

  In the above, the sub fuel injection amount control means for controlling the sub fuel injection amount, and the target sub fuel injection amount calculation that calculates the target sub fuel injection amount that is the target value of the sub fuel injection amount based on the operating state of the internal combustion engine. And a means. When the sub fuel injection execution timing is retarded from the target sub fuel injection timing, the sub fuel injection amount control means may control the sub fuel injection amount to an amount smaller than the target sub fuel injection amount.

  As described above, when the execution timing of the auxiliary fuel injection is retarded, the interval between the execution timing of the auxiliary fuel injection and the execution timing of the main fuel injection is shortened. Therefore, the main fuel injection is easily performed in a state where oxygen is consumed for the combustion of the fuel injected by the auxiliary fuel injection. As a result, there is a risk of increasing the amount of particulate matter (hereinafter referred to as PM).

Therefore, the amount of oxygen consumed for the combustion of the fuel injected by the sub fuel injection is reduced by reducing the sub fuel injection amount. Thereby, generation | occurrence | production of PM can be suppressed.

  Therefore, according to the above, it is possible to suppress an increase in PM even when the execution timing of the auxiliary fuel injection is delayed from the target auxiliary fuel injection timing.

  Here, as the execution timing of the auxiliary fuel injection is later, that is, the interval between the execution timing of the auxiliary fuel injection and the execution timing of the main fuel injection is shorter, the oxygen at the time of combustion of the fuel injected by the main fuel injection is insufficient. Easy to do. For this reason, the PM is likely to increase as the execution timing of the auxiliary fuel injection is later.

  Therefore, in the above, when the sub fuel injection amount is controlled to be smaller than the target sub fuel injection amount, the sub fuel injection amount may be controlled to be smaller as the sub fuel injection execution timing is later. Thereby, the amount of sub fuel injection can be made more suitable for the interval between the execution timing of sub fuel injection and the execution timing of main fuel injection.

  When it is attempted to increase the supercharging pressure to the target supercharging pressure with a change in the operating state of the internal combustion engine, the actual supercharging pressure may temporarily exceed the target supercharging pressure. As the supercharging pressure increases, the amount of intake air increases, so even if the amount of EGR gas is increased, the possibility of causing an increase in the amount of unburned combustion emissions and misfire is reduced.

  Therefore, in the present invention, when the actual supercharging pressure detected by the supercharging pressure detection means is higher than the target supercharging pressure when the operating state of the internal combustion engine is a transient operation state, the EGR gas amount control means The EGR gas amount may be controlled to be larger than the target EGR gas amount.

  According to this, in the case where the actual supercharging pressure becomes higher than the target supercharging pressure when the operation state of the internal combustion engine is a transient operation state, the increase in the amount of unburned fuel and the misfire are suppressed. The amount of NOx emission can be further reduced.

  Further, in this case, when the actual supercharging pressure is higher than the target supercharging pressure when the operating state of the internal combustion engine is a transient operating state, the EGR gas amount is increased as the actual supercharging pressure increases. You may control. Thereby, the amount of EGR gas can be set to an amount more suitable for the actual supercharging pressure.

  In the above, when the fuel injection valve directly injects fuel into the cylinder of the internal combustion engine, the fuel injection timing control means for controlling the fuel injection timing by the fuel injection valve and the target which is the target value of the fuel injection timing Target fuel injection timing calculation means for calculating the fuel injection timing based on the operating state of the internal combustion engine may be further included.

  When the EGR gas amount is controlled to be larger than the target EGR gas amount, the fuel injection timing may be retarded from the target fuel injection timing.

  The exhaust gas temperature can be raised by retarding the fuel injection timing. Therefore, according to the above, even if the increase in PM is caused by increasing the amount of EGR gas, the oxidation of the PM can be promoted.

  Therefore, according to the above, even when the EGR gas amount is controlled to be larger than the target EGR gas amount, the amount of PM discharged to the outside can be further suppressed.

  Here, the greater the amount of EGR gas, the more easily the PM increases. The exhaust temperature can be increased as the fuel injection timing is later.

Therefore, in the above, when the fuel injection timing is retarded from the target fuel injection timing, EGR
The fuel injection timing may be controlled to be later as the amount of gas increases. According to this, since the exhaust gas temperature can be increased as the EGR gas amount increases, the amount of PM discharged to the outside can be further suppressed.

  According to the present invention, in an exhaust gas purification system for an internal combustion engine provided with a supercharger and an EGR device, when the operation state of the internal combustion engine becomes a transient operation state, the amount of unburned fuel is suppressed while suppressing the NOx emission amount. Increase in emissions and misfire can be suppressed.

  Hereinafter, specific embodiments of an exhaust gas purification system for an internal combustion engine according to the present invention will be described with reference to the drawings.

<Schematic configuration of internal combustion engine and intake / exhaust system thereof>
FIG. 1 is a diagram showing a schematic configuration of an internal combustion engine and its intake / exhaust system according to the present embodiment. The internal combustion engine 1 is a diesel engine for driving a vehicle having four cylinders 2. Each cylinder 2 is provided with a fuel injection valve 3 for directly injecting fuel into the cylinder 2.

  An intake manifold 5 and an exhaust manifold 7 are connected to the internal combustion engine 1. One end of an intake passage 4 is connected to the intake manifold 5. One end of an exhaust passage 6 is connected to the exhaust manifold 7.

  A compressor 8 a of a turbocharger (supercharger) 8 is installed in the intake passage 4. A turbine 8 b of a turbocharger 8 is installed in the exhaust passage 6.

  The intake manifold 5 is provided with a pressure sensor 14 for detecting a supercharging pressure.

  On the downstream side of the turbine 8b in the exhaust passage 6, a particulate filter (hereinafter referred to as a filter) 9 for collecting PM in the exhaust is provided. The filter 9 carries an NOx storage reduction catalyst (hereinafter referred to as NOx catalyst). Further, a temperature sensor 15 that detects the temperature of the exhaust gas is provided downstream of the filter 9 in the exhaust passage 6.

  The internal combustion engine 1 according to this embodiment includes an EGR device 11 that introduces at least a part of exhaust gas into the intake system as EGR gas. The EGR device 11 includes an EGR passage 12 having one end connected to the exhaust manifold 7 and the other end connected to the intake manifold 5. EGR gas is introduced from the exhaust manifold 7 into the intake manifold 5 through the EGR passage 12. The EGR passage 12 is provided with an EGR valve 13 that controls the amount of EGR gas introduced into the intake manifold 5.

  The internal combustion engine 1 is provided with an electronic control unit (ECU) 10. The ECU 10 is a unit that controls the operation state of the internal combustion engine 1 in accordance with the operation conditions of the internal combustion engine 1 and the request of the driver. A pressure sensor 14, a temperature sensor 15, a crank position sensor 16, and an accelerator opening sensor 17 are electrically connected to the ECU 10. The crank position sensor 16 detects the crank angle of the internal combustion engine 1. The accelerator opening sensor 17 detects the accelerator opening of a vehicle on which the internal combustion engine 1 is mounted. And the output signal of each said sensor is input into ECU10.

The ECU 10 estimates the temperature of the filter 9 based on the detection value of the temperature sensor 15. In the ECU 10, the crank position sensor 16 derives the rotational speed of the internal combustion engine 1, and derives the load of the internal combustion engine 1 based on the detected value of the accelerator opening sensor 17.

  In addition, the fuel injection valve 3 and the EGR valve 13 are electrically connected to the ECU 10. These are controlled by the ECU 10.

  In the present embodiment, the fuel injection valve 3 performs main fuel injection at a timing near the top dead center of the compression stroke, and further performs sub fuel injection at a timing earlier than the main fuel injection in one combustion cycle. The ECU 10 controls the main fuel injection amount and the sub fuel injection amount, the main fuel injection execution timing (hereinafter referred to as main fuel injection timing), and the sub fuel injection execution timing (hereinafter referred to as sub fuel injection timing).

  In the present embodiment, the EGR gas amount is controlled by controlling the opening degree of the EGR valve 13 by the ECU 10.

<Control of supercharging pressure, EGR gas amount, main fuel injection amount, sub fuel injection amount, main fuel injection timing, sub fuel injection timing>
Next, a control routine for controlling the supercharging pressure and the EGR gas amount, the main fuel injection amount, the sub fuel injection amount, the main fuel injection timing, and the sub fuel injection timing according to this embodiment is based on the flowchart shown in FIG. I will explain. This routine is stored in the ECU 10 in advance, and is repeatedly executed at predetermined intervals (for example, every rotation of the crankshaft of the internal combustion engine 1) during operation of the internal combustion engine 1.

  In this routine, first, in S101, the ECU 10 detects the operating state (rotation speed, load, etc.) of the internal combustion engine 1.

  Next, the ECU 10 proceeds to S102, and sets the target main fuel injection amount Qfmaint and the target sub fuel injection amount Qfsubt, the target main fuel injection timing tmaint, the target injection interval Δtinjt, the target boost pressure Pint, and the target EGR gas amount Qgt. 1 is calculated based on the operating state of 1. The relationship between these values and the operating state of the internal combustion engine 1 is stored in advance in the ECU 10 as a map.

  The target injection interval Δtinjt is a target value of an injection interval that is an interval between the main fuel injection timing and the sub fuel injection timing.

  Next, the ECU 10 proceeds to S103. When the operation state of the internal combustion engine 1 becomes a transient operation, the respective target values change. However, the response delay of the supercharging pressure is larger than the response delay of the fuel injection amount, fuel injection timing, and EGR gas amount. Therefore, in this embodiment, as will be described later, the auxiliary fuel injection amount and the main fuel injection timing are based on the supercharging pressure ratio RPin that is the ratio (Pinm / Pint) of the actual supercharging pressure Pinm to the target supercharging pressure Pint. The auxiliary fuel injection timing and the EGR gas amount are corrected.

  First, in S103, the ECU 10 calculates the supercharging pressure ratio RPin from the target supercharging pressure Pint and the actual supercharging pressure Pinm detected by the pressure sensor 14 at the present time.

  Next, the ECU 10 proceeds to S104 and determines whether or not the supercharging pressure ratio RPin is smaller than 1. If an affirmative determination is made in S104, the ECU 10 proceeds to S105, and if a negative determination is made, the ECU 10 proceeds to S112.

In step S105, the ECU 10 sets the correction coefficient a1 for correcting the EGR gas amount, the correction period b for correcting the injection interval, and the correction amount c for correcting the auxiliary fuel injection amount to the boost pressure ratio RPin and the internal combustion engine. It is calculated based on the rotational speed Ne of 1.

  The relationship among the correction coefficient a1, the correction period b, and the correction amount c, the supercharging pressure ratio RPin, and the rotational speed Ne of the internal combustion engine 1 is stored in advance in the ECU 10 as first, second, and third maps. Then, the ECU 10 calculates a correction coefficient a1, a correction period b, and a correction amount c based on each map.

  In the first, second, and third maps, the supercharging pressure RPin has a value of 1 or less. In the first map, when the supercharging pressure ratio RPin is 1, the correction coefficient a1 is 1, and when the supercharging pressure ratio RPin is smaller than 1, the correction coefficient a1 is a positive value smaller than 1. When the supercharging pressure ratio RPin is smaller than 1, the correction coefficient a1 is smaller as the supercharging pressure ratio RPin is smaller, and is larger as the rotational speed Ne of the internal combustion engine 1 is higher.

  In the second map, the correction period b is 0 when the boost pressure ratio RPin is 1, and the correction period b is greater than 0 when the boost pressure ratio RPin is less than 1. When the supercharging pressure ratio RPin is smaller than 1, the correction period b becomes larger as the supercharging pressure ratio RPin becomes smaller, and becomes smaller as the rotational speed Ne of the internal combustion engine 1 becomes higher.

  In the third map, the correction amount c is 0 when the boost pressure ratio RPin is 1, and the correction amount c is greater than 0 when the boost pressure ratio RPin is less than 1. Further, when the supercharging pressure ratio RPin is smaller than 1, the correction amount c increases as the supercharging pressure ratio RPin decreases, and decreases as the rotational speed Ne of the internal combustion engine 1 increases.

  Next, the ECU 10 proceeds to S106, and calculates the corrected EGR gas amount Qgc1 by multiplying the target EGR gas amount Qgt by the correction coefficient a1 calculated in S105. At this time, the corrected EGR gas amount Qgc1 is inevitably smaller than the target EGR gas amount Qgt.

  Next, the ECU 10 proceeds to S107, and controls the opening degree of the EGR valve 13 so that the EGR gas amount introduced into the intake manifold 5 becomes the corrected EGR gas amount Qgc1. That is, the opening of the EGR valve 13 is set to a smaller opening than when the EGR gas amount is controlled to the target EGR gas amount.

  Next, the ECU 10 proceeds to S108, and calculates a corrected injection interval Δtinjc by subtracting the correction period b calculated in S105 from the target injection interval Δtinjt.

  Next, the ECU 10 proceeds to S109 and corrects the auxiliary fuel injection timing so that the injection interval becomes the corrected injection interval Δtinjc. That is, the sub fuel injection timing is retarded from when the injection interval is controlled to the target injection interval (the sub fuel injection timing at this time corresponds to the target sub fuel injection timing according to the present invention).

  Next, the ECU 10 proceeds to S110, and calculates a corrected sub fuel injection amount Qsubc by subtracting the correction amount c calculated in S105 from the target sub fuel injection amount Qfsubt.

  Next, the ECU 10 proceeds to S111 and controls the sub fuel injection amount to the corrected sub fuel injection amount Qsubc. That is, the sub fuel injection amount is controlled to an amount smaller than the target sub fuel injection amount Qsubt. Thereafter, the ECU 10 once terminates execution of this routine.

  On the other hand, the ECU 10 that has proceeded to S112 determines whether or not the supercharging pressure ratio RPin is greater than 1. If an affirmative determination is made in S112, the ECU 10 proceeds to S113. On the other hand, if a negative determination is made in S112, the ECU 10 once ends the execution of this routine. When the execution of this routine is terminated at this point, the ECU 10 determines that it is not necessary to correct the main fuel injection amount and the auxiliary fuel injection amount, the main fuel injection timing, the injection interval, and the EGR gas amount, and these are determined in S102. Control to each calculated target value.

  The ECU 10 having proceeded to S113 determines whether or not the temperature Tc of the filter 9 is equal to or higher than a predetermined temperature Tca. Here, the predetermined temperature Tca is a predetermined temperature that is equal to or higher than the lower limit value of the activation temperature of the NOx catalyst carried on the filter 9. That is, when the temperature of the filter 9 is equal to or higher than the predetermined temperature Tca, it can be determined that the supported NOx catalyst is activated. If a negative determination is made in S113, the ECU 10 proceeds to S114. On the other hand, when an affirmative determination is made in S113, the ECU 10 once ends the execution of this routine. When the execution of this routine is terminated at this point, the ECU 10 needs to correct the main fuel injection amount and the auxiliary fuel injection amount, the main fuel injection timing, the injection interval, and the EGR gas amount as in the case where a negative determination is made in S112. These are determined to be not, and are controlled to the target values calculated in S102.

  The ECU 10 having advanced to S114 calculates a correction coefficient a2 for correcting the EGR gas amount and a correction period d for correcting the main fuel injection timing based on the supercharging pressure ratio RPin and the rotational speed of the internal combustion engine 1.

  The relationship between each of the correction coefficient a2 and the correction period d, the supercharging pressure ratio RPin, and the rotational speed of the internal combustion engine 1 is stored in advance in the ECU 10 as fourth and fifth maps. Then, the ECU 10 calculates the correction coefficient a2 and the correction period d based on each map.

  In the fourth and fifth maps, the supercharging pressure RPin has a value of 1 or more. In the fourth map, the correction coefficient a2 is 1 when the boost pressure ratio RPin is 1. When the boost pressure ratio RPin is greater than 1, the correction coefficient a2 increases as the boost pressure ratio RPin increases, and increases as the rotational speed Ne of the internal combustion engine 1 increases.

  In the fifth map, the correction period d is 0 when the boost pressure ratio RPin is 1. When the boost pressure ratio RPin is greater than 1, the correction period b increases as the boost pressure ratio RPin increases, and increases as the rotational speed Ne of the internal combustion engine 1 increases.

  Next, the ECU 10 proceeds to S115, and calculates a corrected EGR gas amount Qgc2 by multiplying the target EGR gas amount Qgt by the correction coefficient a2 calculated in S114. At this time, the corrected EGR gas amount Qgc2 is necessarily larger than the target EGR gas amount Qgt.

  Next, the ECU 10 proceeds to S116 and controls the opening degree of the EGR valve 13 so that the EGR gas amount introduced into the intake manifold 5 becomes the corrected EGR gas amount Qgc2. That is, the opening degree of the EGR valve 13 is set to a larger opening degree than when the EGR gas amount is controlled to the target EGR gas amount.

  Next, the ECU 10 proceeds to S117, and calculates the corrected main fuel injection timing tmainc by adding the correction period d calculated in S114 to the target main fuel injection timing tmaint.

Next, the ECU 10 proceeds to S118 and controls the main fuel injection timing to the corrected main fuel injection timing tmainc. That is, the main fuel injection timing is retarded from the target main fuel injection timing tmaint. In this case, the auxiliary fuel injection timing is controlled so that the injection interval becomes the target injection interval Δtinjt. Thereafter, the ECU 10 once terminates execution of this routine.

  According to the routine described above, when the operation state of the internal combustion engine 1 becomes a transient operation state, the supercharging pressure ratio RPin becomes smaller than 1, that is, the actual supercharging pressure Pinm is higher than the target supercharging pressure Pint. When it is low, the EGR gas amount is corrected to an amount smaller than the target EGR gas amount Qgt. Thereby, it is possible to prevent the amount of EGR gas introduced into the intake manifold 5 from being excessively large with respect to the actual supercharging pressure Pinm when the operating state of the internal combustion engine is a transient operating state. That is, it is possible to suppress the EGR gas amount from being excessively larger than the actual intake air amount.

  Therefore, according to the present embodiment, when the operation state of the internal combustion engine 1 becomes a transient operation state, it is possible to suppress an increase in the amount of unburned fuel and a misfire while suppressing the amount of NOx emission. .

  Further, according to the above routine, when the EGR gas amount is corrected to be smaller than the target EGR gas amount Qgt, the EGR gas amount is controlled to be smaller as the actual supercharging pressure Pinm is lower. Thereby, the amount of EGR gas can be set to an amount more suitable for the actual supercharging pressure.

  Further, the intake air amount increases as the rotational speed of the internal combustion engine 1 increases. Therefore, according to the above routine, when the EGR gas amount is corrected to an amount smaller than the target EGR gas amount Qgt, the EGR gas amount is controlled to be smaller as the rotational speed Ne of the internal combustion engine 1 is lower.

  Further, according to the above routine, when the actual boost pressure Pinm is lower than the target boost pressure Pint, the injection interval is corrected to a time shorter than the target injection interval Δtinjt by retarding the auxiliary fuel injection timing. . Thereby, the fuel injected by the auxiliary fuel injection becomes easy to burn. Therefore, it is possible to prevent the amount of unburned fuel from increasing or misfire from occurring due to the difficulty in burning the fuel injected by the auxiliary fuel injection.

  Further, according to the above routine, when the injection interval is corrected to a time shorter than the target injection interval Δtinjt, the injection interval is controlled to be shorter as the actual supercharging pressure Pinm is lower. That is, the smaller the intake air amount, the more retarded the auxiliary fuel injection timing. Thereby, the fuel injected by the auxiliary fuel injection can be made easier to burn.

  Further, according to the above routine, when the injection interval is corrected to a time shorter than the target injection interval Δtinjt, the intake air amount decreases as the rotational speed Ne of the internal combustion engine 1 decreases, so that the injection interval is controlled to a shorter time. Is done.

  Furthermore, according to the above routine, when the actual supercharging pressure Pinm is lower than the target supercharging pressure Pint, the sub fuel injection amount is corrected to an amount smaller than the target sub fuel injection amount Qsubt. That is, when the injection interval is corrected to a time shorter than the target injection interval Δtinjt, the sub fuel injection amount is corrected to an amount smaller than the target sub fuel injection amount Qsubt.

When the injection interval is shortened, the main fuel injection is easily performed in a state where oxygen is consumed for combustion of the fuel injected by the sub fuel injection. At this time, the amount of oxygen consumed for the combustion of the fuel injected by the auxiliary fuel injection can be reduced by reducing the auxiliary fuel injection amount. That is, the amount of oxygen that can be used for combustion of the fuel injected by the main fuel injection can be increased. Therefore, by correcting the sub fuel injection amount to an amount smaller than the target sub fuel injection amount Qsubt, an increase in PM can be suppressed even when the injection interval is made shorter than the target injection interval Δtinjt. .

  Further, according to the above routine, when the sub fuel injection amount is corrected to an amount smaller than the target sub fuel injection amount Qsubt, the sub fuel injection amount is controlled to be smaller as the actual supercharging pressure Pinm is lower. . That is, the shorter the injection interval, the smaller the sub fuel injection amount is controlled. Therefore, it is possible to further suppress the shortage of oxygen necessary for the combustion of the fuel injected by the main fuel injection. Therefore, by controlling the sub fuel injection amount as described above, the sub fuel injection amount can be made more suitable for the injection interval, and as a result, the increase in PM can be further suppressed.

  According to the above routine, as described above, when the injection interval is corrected to a time shorter than the target injection interval Δtinjt, the injection interval is controlled to be shorter as the rotational speed Ne of the internal combustion engine 1 is lower. . Therefore, when the sub fuel injection amount is corrected to an amount smaller than the target sub fuel injection amount Qsubt, the lower the rotation speed Ne of the internal combustion engine 1, that is, the shorter the injection interval, the smaller the sub fuel injection amount. Controlled.

  Further, according to the above routine, when the operation state of the internal combustion engine 1 becomes a transient operation state, the supercharging pressure ratio RPin becomes larger than 1, that is, the actual supercharging pressure Pinm is higher than the target supercharging pressure Pint. When the temperature is high and the temperature Tc of the filter 9 is lower than the predetermined temperature Tca, the EGR gas amount is corrected to an amount larger than the target EGR gas amount Qgt.

  When the supercharging pressure increases, the amount of intake air increases, so even if the amount of EGR gas is increased, it becomes difficult to cause an increase in the amount of unburned fuel and misfire. Moreover, the amount of NOx emission can be further reduced as the amount of EGR gas is increased. Therefore, when the actual boost pressure Pinm is higher than the target boost pressure Pint, the increase in the amount of unburned fuel and misfire are suppressed by correcting the EGR gas amount to an amount larger than the target EGR gas amount Qgt. However, the amount of NOx emission can be further reduced.

  Further, according to the above routine, when the EGR gas amount is corrected to an amount larger than the target EGR gas amount Qgt, the EGR gas amount is controlled to be larger as the actual supercharging pressure Pinm is higher. Thereby, the amount of EGR gas can be set to an amount more suitable for the actual supercharging pressure.

  Further, since the intake air amount increases as the rotational speed of the internal combustion engine 1 increases, according to the above routine, when the EGR gas amount is corrected to an amount larger than the target EGR gas amount Qgt, the rotational speed of the internal combustion engine 1 is increased. The higher the Ne, the more the EGR gas amount is controlled.

  Further, in the above routine, when the actual supercharging pressure Pinm is higher than the target supercharging pressure Pint and the temperature Tc of the filter 9 is lower than the predetermined temperature Tca, the main fuel injection timing is the target main injection timing. It is retarded from the fuel injection timing tmaint. That is, when the EGR gas amount is corrected to an amount larger than the target EGR gas amount Qgt, the main fuel injection timing is retarded from the target main fuel injection timing tmaint.

  The exhaust gas temperature can be raised by retarding the main fuel injection timing. Therefore, even when the increase in PM is caused by increasing the EGR gas amount from the target EGR gas amount Qgt, the main fuel injection timing is retarded from the target main fuel injection timing tmaint, whereby the PM It becomes possible to promote the oxidation of. Therefore, the amount of PM discharged to the outside can be suppressed.

Further, according to the above routine, when the main fuel injection timing is retarded from the target main fuel injection timing, the main fuel injection timing is retarded as the actual supercharging pressure Pinm increases. That is, the main fuel injection timing is retarded as the EGR gas amount increases. Thus, the exhaust gas temperature can be increased as the amount of EGR gas increases. Therefore, by controlling the main fuel injection timing as described above, the amount of PM discharged to the outside can be further suppressed.

  Further, according to the above routine, as described above, when the EGR gas amount is corrected to an amount larger than the target EGR gas amount Qgt, the EGR gas amount becomes larger as the rotational speed Ne of the internal combustion engine 1 is higher. Be controlled. Therefore, when the main fuel injection timing is retarded from the target main fuel injection timing tmaint, the main fuel injection timing is delayed more as the rotational speed Ne of the internal combustion engine 1 is higher, that is, as the EGR gas amount is larger. The

  When the temperature of the filter 9 is equal to or higher than the predetermined temperature Tca, the NOx catalyst carried on the filter 9 is activated, so that NOx in the exhaust can be stored in the NOx catalyst. Therefore, in this embodiment, even when the actual boost pressure Pinm is higher than the target boost pressure Pint, if the temperature of the filter 9 is equal to or higher than the predetermined temperature Tca, the EGR gas amount is set to the target EGR gas. No correction is made to make it larger than the amount Qgt. Thereby, the increase in PM is suppressed.

The figure which shows schematic structure of the internal combustion engine which concerns on an Example, and its intake / exhaust system. The flowchart which shows the control routine for controlling the supercharging pressure and EGR gas amount, main fuel injection amount, sub fuel injection amount, main fuel injection timing, and sub fuel injection timing which concern on an Example.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Internal combustion engine 2 ... Cylinder 3 ... Fuel injection valve 4 ... Intake passage 5 ... Intake manifold 6 ... Exhaust passage 7 ... Exhaust manifold 8 ... Turbocharger 8a -Compressor 8b-Turbine 9 ... Particulate filter 10-ECU
11. EGR device 12 EGR passage 13 EGR valve 14 Pressure sensor 15 Temperature sensor 16 Crank position sensor 17 Accelerator opening sensor

Claims (10)

An EGR device that introduces at least part of the exhaust gas of the internal combustion engine into the intake system of the internal combustion engine as EGR gas;
A supercharger that supercharges intake air using the energy of the exhaust gas of the internal combustion engine;
EGR gas amount control means for controlling the amount of EGR gas introduced into the intake system of the internal combustion engine by the EGR device;
A target EGR gas amount calculating means for calculating a target EGR gas amount which is a target value of the EGR gas amount based on an operating state of the internal combustion engine;
A target boost pressure calculating means for calculating a target boost pressure which is a target value of the boost pressure based on the operating state of the internal combustion engine;
A supercharging pressure detecting means for detecting the actual supercharging pressure,
When the actual supercharging pressure detected by the supercharging pressure detecting means is lower than the target supercharging pressure when the operating state of the internal combustion engine is in a transient operating state, the EGR gas amount control means Is controlled to an amount smaller than the target EGR gas amount.   The EGR gas amount control means, when controlling the EGR gas amount to an amount smaller than the target EGR gas amount, controls the EGR gas amount to a smaller amount as the actual supercharging pressure is lower. An exhaust purification system for an internal combustion engine according to claim 1. A fuel injection valve for directly injecting fuel into the cylinder of the internal combustion engine;
Sub fuel injection execution means for executing sub fuel injection at a time prior to main fuel injection performed at a time near the top dead center of the compression stroke by the fuel injection valve;
Sub fuel injection timing control means for controlling the execution timing of sub fuel injection by the sub fuel injection execution means;
A target sub fuel injection timing calculating means for calculating a target sub fuel injection timing, which is a target value of the execution timing of the sub fuel injection, based on the operating state of the internal combustion engine,
When the actual supercharging pressure detected by the supercharging pressure detecting means is lower than the target supercharging pressure when the operating state of the internal combustion engine is in a transient operating state, the auxiliary fuel injection timing control means 3. The exhaust gas purification system for an internal combustion engine according to claim 1, wherein the injection execution timing is retarded from the target sub fuel injection timing.   When the sub fuel injection execution timing control means retards the sub fuel injection execution timing from the target sub fuel injection timing, the sub fuel injection execution timing control means controls the sub fuel injection execution timing to be later as the actual supercharging pressure is lower. The exhaust gas purification system for an internal combustion engine according to claim 3. Sub fuel injection amount control means for controlling the sub fuel injection amount;
A target sub fuel injection amount calculating means for calculating a target sub fuel injection amount that is a target value of the sub fuel injection amount based on an operating state of the internal combustion engine;
The sub fuel injection amount control means controls the sub fuel injection amount to an amount smaller than the target sub fuel injection amount when the execution timing of the sub fuel injection is delayed from the target sub fuel injection timing. The exhaust gas purification system for an internal combustion engine according to claim 3 or 4.   When the sub fuel injection amount control means controls the sub fuel injection amount to be smaller than the target sub fuel injection amount, the sub fuel injection amount control means controls the sub fuel injection amount to be smaller as the sub fuel injection execution timing is later. 6. An exhaust purification system for an internal combustion engine according to claim 5, When the actual supercharging pressure detected by the supercharging pressure detecting means is higher than the target supercharging pressure when the operating state of the internal combustion engine is in a transient operating state, the EGR gas amount control means
The exhaust gas purification system for an internal combustion engine according to claim 1, wherein the gas amount is controlled to be larger than a target EGR gas amount.   The EGR gas amount control means, when controlling the EGR gas amount to an amount larger than a target EGR gas amount, controls the EGR gas amount to a larger amount as the actual supercharging pressure is higher. 8. An exhaust purification system for an internal combustion engine according to claim 7. A fuel injection valve for directly injecting fuel into the cylinder of the internal combustion engine;
Fuel injection timing control means for controlling the fuel injection timing by the fuel injection valve;
A target fuel injection timing calculating means for calculating a target fuel injection timing, which is a target value of the fuel injection timing, based on an operating state of the internal combustion engine;
9. The fuel injection timing control means according to claim 7 or 8, wherein the fuel injection timing control means retards the fuel injection timing from the target fuel injection timing when the EGR gas amount is controlled to be larger than the target EGR gas amount. An exhaust purification system for an internal combustion engine. 10. The internal combustion engine according to claim 9, wherein the fuel injection timing control means controls the fuel injection timing to a later timing as the EGR gas amount increases when the fuel injection timing is retarded from the target fuel injection timing. Engine exhaust purification system.

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