JP2007303437A - Control device for internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To effectively reduce emission by performing internal EGR and external EGR at an optimal ratio under stable operation condition and surely avoid an adverse effect of EGR at the time of load change, in a control device for an internal combustion engine. <P>SOLUTION: When increase of engine load is estimated, ratio of internal EGR quantity to total EGR quantity is set higher right before the increase (time t1 to t2). Consequently, when engine load actually increases, total EGR rate can be immediately reduced by changing valve timing of an intake and an exhaust valve. Emission of smoke, thereby, can be effectively inhibited since shortage of oxygen in a cylinder right after increase of engine load can be avoided. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a control device for an internal combustion engine.

  A technique for performing external EGR (Exhaust Gas Recirculation) in an internal combustion engine such as a diesel engine is known. The external EGR is a technique in which a part of the exhaust gas is returned to the intake passage through the external EGR passage connecting the intake passage and the exhaust passage and mixed with the intake air. By performing external EGR, the amount of NOx emission can be reduced. The amount of external EGR is normally adjusted by the opening degree of an EGR valve provided in the external EGR passage or an intake throttle valve.

  When a large torque is required, such as when the vehicle is accelerating or climbing a hill, it is necessary to reduce the EGR rate in order to secure a large amount of air to be taken into the cylinder. However, since the volume of the EGR path such as the external EGR passage is large in the external EGR, even if the EGR valve or the intake throttle valve is moved, the exhaust gas remaining in the EGR path is taken into the intake air for several cycles thereafter. Continue mixing. That is, in the case of external EGR, the EGR rate cannot be reduced immediately. For this reason, the EGR rate becomes higher than the target value at the initial stage of acceleration or immediately after the start of climbing, and as a result, smoke is easily discharged.

  In order to suppress such smoke emissions, it is necessary to limit the fuel injection amount at the beginning of acceleration or immediately after the start of climbing. However, if the fuel injection amount is limited, the torque becomes insufficient, and the required acceleration feeling and climbing performance Can not be satisfied. On the other hand, when the EGR rate during steady operation is reduced in preparation for acceleration or climbing, the NOx emission amount increases. Further, when the injection timing is retarded in order to suppress the increase in the NOx emission amount, the fuel consumption is deteriorated.

  Incidentally, EGR includes internal EGR in addition to the above-described external EGR. By providing a state where the exhaust valve and the intake valve are both open (positive valve overlap) or closed (negative valve overlap) between the exhaust stroke and the intake stroke, EGR can be performed. The amount of the internal EGR can be adjusted by changing the valve timing by a variable valve timing mechanism.

  In Japanese Patent Application Laid-Open No. 2004-251201, a case where the vehicle is in a light load range is referred to as “a case where it is necessary to perform a rapid increase control of the intake fresh air amount with respect to a rapid acceleration”. An apparatus that controls to perform only internal EGR is disclosed (see paragraphs 0020 and 0027 of the same publication). Unlike the case of external EGR, in the case of internal EGR, the EGR amount can be immediately reduced by changing the valve timing. According to the above-described conventional apparatus, the external EGR is stopped and only the internal EGR is performed when in the light load range. Therefore, when a sudden acceleration request is generated, the EGR rate is changed by changing the valve timing. Can be reduced immediately. For this reason, it is possible to prevent the discharge of smoke at the early stage of acceleration while avoiding the EGR reduction during the steady operation.

JP 2004-251201 A JP 2004-293392A

  By the way, FIG. 13 is a figure which shows the relationship between the combustion area | region of diesel, a soot (Soot) production | generation area | region, and a NOx production | generation area | region. In FIG. 13, the horizontal axis represents temperature, and the vertical axis represents the equivalent ratio of fuel to air. As can be seen from the figure, the higher the in-cylinder temperature, the greater the overlap between the diesel combustion region, the soot generation region and the NOx generation region. For this reason, it becomes easy to discharge smoke and NOx.

  In general, even if the total EGR rate including the internal EGR and the external EGR is the same, the in-cylinder temperature increases as the proportion of the internal EGR increases. In the case of the external EGR, the temperature of the exhaust gas recirculating can be lowered by the EGR cooler provided in the middle of the external EGR passage, whereas in the case of the internal EGR, the exhaust gas has a high temperature. It is because it recirculates as it is.

  As described above, in the conventional apparatus, in order to prepare for acceleration in the light load region, the external EGR is always stopped and only the internal EGR is performed. For this reason, according to the control of the conventional apparatus, the in-cylinder temperature tends to be high even in the light load region even at the same EGR rate. As a result, there is a problem that the amount of smoke and NOx emission is likely to increase even if the same EGR rate is ensured as compared with the case where external EGR is used.

  The present invention has been made to solve the above-described problems. In a steady operation state, the internal EGR and the external EGR can be effectively reduced by performing an optimum ratio, and the load can be effectively reduced. It is an object of the present invention to provide a control device for an internal combustion engine that can surely avoid an adverse effect of EGR when changing.

In order to achieve the above object, a first invention is a control device for an internal combustion engine,
An external EGR means for recirculating exhaust gas through an external EGR passage connecting the exhaust passage and the intake passage of the internal combustion engine;
Internal EGR means for generating EGR inside the internal combustion engine without passing through the external EGR passage;
An internal / external ratio adjusting means for adjusting a ratio between the internal EGR amount and the external EGR amount;
Load change prediction means for predicting changes in engine load in advance;
A target value setting means for setting a target value of a ratio between the internal EGR amount and the external EGR amount in order to prepare for the engine load change according to the predicted change in the engine load;
An internal / external ratio control means for controlling the internal / external ratio adjusting means so that the ratio between the internal EGR amount and the external EGR amount becomes the target value immediately before the predicted change in engine load actually occurs. ,
It is characterized by providing.

The second invention is the first invention, wherein
When an increase in engine load is predicted, the target value is set such that the ratio of the internal EGR amount to the total EGR amount is higher than that during normal operation.

The third invention is the first or second invention, wherein
The target value setting means includes means for setting the target value in accordance with the predicted degree of change in engine load.

According to a fourth invention, in any one of the first to third inventions,
When an increase in engine load is predicted, the target value is a value such that the greater the degree of increase in engine load, the higher the ratio of the internal EGR amount to the total EGR amount. To do.

According to a fifth invention, in any one of the first to fourth inventions,
When control is performed so that the ratio between the internal EGR amount and the external EGR amount becomes the target value immediately before the predicted change in engine load actually occurs, the ratio of the internal EGR amount to the total EGR amount is high. It is further characterized by further comprising a total EGR rate control means for controlling the total EGR rate so that the total EGR rate decreases.

According to a sixth invention, in any one of the first to fifth inventions,
When control is performed so that the ratio between the internal EGR amount and the external EGR amount becomes the target value immediately before the predicted change in engine load actually occurs, the amount of oxygen in the cylinder when the intake valve is closed or In-cylinder oxygen stabilizing means for controlling the total EGR rate is further provided so that the oxygen concentration becomes substantially constant before and after the control.

According to a seventh invention, in any one of the first to sixth inventions,
When the ratio between the internal EGR amount and the external EGR amount is controlled to be the target value immediately before the predicted change in engine load actually occurs, the greater the degree of change in the ratio, the more It further comprises an internal / external ratio change start timing setting means for accelerating the time point at which the ratio starts to change.

Further, an eighth invention is any one of the first to seventh inventions,
The load change prediction means includes
Road information output means for outputting road information in the traveling direction of the vehicle;
Based on the road information, means for predicting that a change in engine load will occur when passing at least one of a slope, a congestion elimination point, and a road toll gate;
It is characterized by including.

According to a ninth invention, in any one of the first to eighth inventions,
The load change prediction means includes
Detecting means for detecting a driver's operation on at least one of a transmission, a clutch, and a brake of the vehicle;
Means for predicting a change in engine load based on the detected operation;
It is characterized by including.

The tenth invention is the ninth invention, wherein
The load change prediction means, when the shift position of the transmission is shifted from neutral to the start stage when the vehicle is stopped, when the clutch pedal is depressed when the vehicle is stopped, when the brake pedal is released when the vehicle is stopped, The engine load is predicted to increase immediately after at least one of the case where the transmission is shifted up during acceleration traveling and the case where the transmission is shifted down during acceleration traveling.

Further, an eleventh aspect of the invention is any one of the first to tenth aspects of the invention,
The internal / external ratio adjusting means controls the internal / external ratio adjusting means so that the ratio between the internal EGR amount and the external EGR amount is returned to the normal operation ratio when the predicted change in engine load does not actually occur. An outside ratio restoring means is further provided.

  According to the first invention, a change in engine load can be predicted in advance. Then, immediately before the predicted change in the engine load actually occurs, the ratio between the internal EGR amount and the external EGR amount can be controlled to be a target value for preparing for the engine load change. For this reason, according to the first aspect of the present invention, the emission can be reduced as much as possible by performing the internal EGR amount and the external EGR amount at an optimum ratio until immediately before the engine load changes. Then, immediately before the engine load change occurs, the ratio between the internal EGR amount and the external EGR amount can be set to a ratio that can quickly respond to the engine load change. For this reason, it is possible to avoid that the EGR has a harmful effect when the engine load change actually occurs, for example, that the emission is deteriorated or the fuel injection amount must be limited.

  According to the second invention, when an increase in engine load is predicted, immediately before the increase in engine load, the ratio of the internal EGR amount to the total EGR amount is higher than that during normal operation. That is, the ratio of the external EGR amount can be made lower than that during normal operation. For this reason, when the engine load increases, the total EGR rate can be rapidly reduced, so that it is possible to reliably prevent a situation where oxygen in the cylinder becomes insufficient with respect to the increased fuel injection amount. Therefore, smoke discharge can be effectively suppressed. Further, since it is not necessary to perform control to limit the fuel injection amount immediately after the engine load increases in order to avoid smoke discharge, it is possible to respond quickly to an increase in required torque and to obtain excellent drivability. Furthermore, the ratio of the external EGR amount to the total EGR amount can be kept high until just before the engine load increases, so that the in-cylinder temperature is low, that is, the exhaust amount of NOx and smoke is kept low. can do.

  According to the third aspect, the target value of the ratio between the internal EGR amount and the external EGR amount immediately before the engine load change can be set according to the predicted degree of change in the engine load. For this reason, the ratio of the internal EGR amount immediately before the engine load change and the external EGR amount can be set to an optimum value according to the predicted degree of change in the engine load. Therefore, according to the third aspect of the present invention, it is possible to more reliably avoid EGR from causing a harmful effect when an engine load change actually occurs.

  According to the fourth aspect of the invention, when the increase in engine load is predicted, the larger the degree of load increase, the higher the ratio of the internal EGR amount to the total EGR amount immediately before the load increase is increased. be able to. As a result, even if the fuel injection amount is significantly increased with the start of steep climbing or sudden acceleration, the total EGR rate is decreased more quickly and a large amount of in-cylinder oxygen is secured. Therefore, smoke emission can be effectively suppressed.

  According to the fifth aspect of the present invention, when the control is performed so that the ratio between the internal EGR amount and the external EGR amount becomes the target value immediately before the predicted change in engine load actually occurs, the internal ratio of the total EGR amount The higher the ratio of the EGR amount, the lower the total EGR rate. Thereby, even if the in-cylinder temperature rises due to the increase in the ratio of the internal EGR, it is possible to reliably avoid an increase in the smoke discharge amount.

  According to the sixth aspect of the invention, when control is performed so that the ratio between the internal EGR amount and the external EGR amount becomes the target value immediately before the predicted change in engine load actually occurs, The total EGR rate can be controlled so that the oxygen amount or oxygen concentration in the cylinder is substantially constant before and after the control. Thereby, even if the ratio of the internal EGR is increased, it is possible to reliably avoid an increase in the smoke discharge amount.

  According to the seventh aspect, when the control is performed so that the ratio between the internal EGR amount and the external EGR amount becomes the target value immediately before the predicted change in the engine load actually occurs, the degree of change in the ratio The larger the is, the earlier the time point at which the ratio starts to change. As a result, even if the degree of change in the ratio is large and it takes a relatively long time to match the ratio to the target value, the ratio is reduced before the expected change in engine load occurs. It is possible to reliably match the target value. In addition, when the degree of changing the ratio is small, the change start time can be delayed. For this reason, it is possible to minimize the time required to increase the ratio of the internal EGR immediately before the engine load increases. That is, the time during which the in-cylinder temperature rises and the amount of NOx or smoke discharged tends to increase can be minimized.

  According to the eighth aspect of the invention, it can be predicted that a change in the engine load will occur when at least one of the slope, the congestion elimination point, and the road toll gate passes based on the road information in the traveling direction of the vehicle. Thereby, the change of the engine load can be accurately predicted.

  According to the ninth aspect, it is possible to predict a change in the engine load based on a driver's operation on at least one of the transmission, clutch, and brake of the vehicle. Thereby, the change of the engine load can be accurately predicted.

  According to the tenth invention, when the shift position of the transmission is shifted from neutral to the starting stage when the vehicle is stopped, when the clutch pedal is depressed when the vehicle is stopped, or when the brake pedal is released when the vehicle is stopped It can be predicted that the engine load increases immediately after at least one of the case where the transmission is shifted up during acceleration traveling and the case where the transmission is shifted down during acceleration traveling. Thereby, an increase in engine load can be accurately predicted.

  According to the eleventh aspect, when the predicted change in engine load does not actually occur, the ratio of the internal EGR amount and the external EGR amount can be returned to the ratio during normal operation. As a result, if it is confirmed that the engine load will change, the ratio between the internal EGR amount and the external EGR amount will be returned to the optimum ratio suitable for steady operation when it is confirmed. Can do.

  Embodiments of the present invention will be described below with reference to the drawings. In addition, the same code | symbol is attached | subjected to the element which is common in each figure, and the overlapping description is abbreviate | omitted.

Embodiment 1 FIG.
[Description of system configuration]
FIG. 1 is a diagram for explaining a system configuration according to the first embodiment of the present invention. The system shown in FIG. 1 includes a four-cycle diesel engine (compression ignition internal combustion engine) 10. It is assumed that the diesel engine 10 is mounted on a vehicle and used as a power source. Although the illustrated diesel engine 10 is an in-line four-cylinder type, in the present invention, the number of cylinders and the cylinder arrangement are not limited thereto.

  In the present embodiment, the case where the present invention is applied to the control of the diesel engine 10 will be described. However, the present invention is not limited to the control of the diesel engine, but a gasoline engine (spark ignition internal combustion engine) or the like. It can be applied to control of various internal combustion engines.

  Each cylinder of the diesel engine 10 is provided with an injector 12 that injects fuel directly into the cylinder. The injectors 12 of each cylinder are connected to a common common rail 14. Fuel in a fuel tank (not shown) is pressurized to a predetermined fuel pressure by a supply pump 16, stored in the common rail 14, and supplied from the common rail 14 to each injector 12.

  An exhaust passage 18 of the diesel engine 10 is branched by an exhaust manifold 20 and connected to an exhaust port 22 (see FIG. 2) of each cylinder. The diesel engine 10 according to this embodiment includes a turbocharger 24. The exhaust passage 18 is connected to the exhaust turbine of the turbocharger 24.

  An exhaust purification device 26 that purifies exhaust gas is provided in the exhaust passage 18 downstream of the turbocharger 24. As the exhaust purification device 26, for example, one of an oxidation catalyst, a NOx storage reduction type or selective reduction type NOx catalyst, a DPF (Diesel Particulate Filter), a DPNR (Diesel Particulate-NOx-Reduction system), or a combination thereof Etc. can be used.

  An air cleaner 30 is provided near the inlet of the intake passage 28 of the diesel engine 10. The air drawn through the air cleaner 30 is compressed by the intake compressor of the turbocharger 24 and then cooled by the intercooler 32. The intake air that has passed through the intercooler 32 is distributed by the intake manifold 34 to the intake ports 35 (see FIG. 2) of the respective cylinders.

  An intake throttle valve 36 is installed between the intercooler 32 and the intake manifold 34 in the intake passage 28. Further, an air flow meter 38 for detecting the amount of intake air is installed in the vicinity of the intake passage 28 downstream of the air cleaner 30.

  One end of an external EGR passage 40 is connected to the intake passage 28 in the vicinity of the intake manifold 34. The other end of the external EGR passage 40 is connected to the vicinity of the exhaust manifold 20 of the exhaust passage 18. In this system, a part of the exhaust gas (burned gas) can be recirculated to the intake passage 28 through the external EGR passage 40, that is, external EGR (Exhaust Gas Recirculation) can be performed. Hereinafter, the exhaust gas recirculated through the external EGR passage 40 is referred to as “external EGR gas”.

  In the middle of the external EGR passage 40, an EGR cooler 42 for cooling the external EGR gas is provided. An EGR valve 44 is provided downstream of the EGR cooler 42 in the external EGR passage 40. As the opening degree of the EGR valve 44 is increased, the amount of exhaust gas passing through the external EGR passage 40, that is, the amount of external EGR can be increased.

  In this system, the external EGR amount and the external EGR rate (the ratio of the external EGR gas in the gas flowing into the cylinder) are determined not only by the opening degree of the EGR valve 44 but also by the opening degree of the intake throttle valve 36. Can be adjusted. When the opening of the intake throttle valve 36 is reduced to throttle the intake air, the intake pressure decreases, so the differential pressure from the back pressure (exhaust pressure) increases. That is, the differential pressure before and after the external EGR passage 40 increases. For this reason, the external EGR amount and the external EGR rate can be increased.

  An intake pressure sensor 46 that detects the intake pressure is installed downstream of the intake throttle valve 36 in the intake passage 28. Further, the present system includes an accelerator opening sensor 48 that detects the amount of depression of the accelerator pedal (accelerator opening) of a vehicle on which the diesel engine 10 is mounted, a shift position sensor 66 that detects a shift position of the transmission, a clutch A clutch pedal sensor 68 that detects depression of the pedal and a brake pedal sensor 70 that detects depression of the brake pedal are provided.

  The system of this embodiment includes an ECU (Electronic Control Unit) 50. The ECU 50 is connected to the various sensors and actuators described above. A navigation system 72 using GPS (Global Positioning System) is connected to the ECU 50. In addition to the signals from the sensors, the ECU 50 is supplied with road information (map information) output from the navigation system 72, traffic information (traffic information) acquired from outside the vehicle by the navigation system 72, and the like. The ECU 50 controls the operating state of the diesel engine 10 by driving each actuator according to a predetermined program based on those signals and information.

  FIG. 2 is a view showing a cross section of one cylinder of the diesel engine 10 in the system shown in FIG. Hereinafter, the diesel engine 10 will be further described. As shown in FIG. 2, a crank angle sensor 62 that detects the rotation angle (crank angle) of the crankshaft 60 is attached in the vicinity of the crankshaft 60 of the diesel engine 10. The crank angle sensor 62 is connected to the ECU 50. According to the signal from the crank angle sensor 62, the engine speed and the like can be detected.

  Further, the diesel engine 10 includes an intake variable valve mechanism 54 that continuously changes the valve timing of the intake valve 52 and an exhaust variable valve mechanism 58 that continuously changes the valve timing of the exhaust valve 56. Is provided. These intake variable valve mechanism 54 and exhaust variable valve mechanism 58 are connected to the ECU 50. Specific configurations of the intake variable valve mechanism 54 and the exhaust variable valve mechanism 58 are not particularly limited. For example, the phase of a cam (not shown) that drives the intake valve 52 and the exhaust valve 56 is continuously variable. A mechanical mechanism such as a mechanism that performs the above can be used. Alternatively, an electromagnetically driven valve or a hydraulically driven valve that can be opened and closed at an arbitrary timing can be used.

(Internal EGR with valve overlap)
In the diesel engine 10 of this embodiment, the magnitude of the negative valve overlap between the intake valve 52 and the exhaust valve 56 can be continuously changed by the intake variable valve mechanism 54 and the exhaust variable valve mechanism 58. . FIG. 3 is a diagram for explaining negative valve overlap. As shown in FIG. 3, the negative valve overlap is a state where both the intake valve 52 and the exhaust valve 56 are closed after the exhaust valve 56 is closed until the intake valve 52 is opened.

  3 is a valve lift diagram of the intake valve 52 and the exhaust valve 56 when no negative valve overlap is provided. From this state, the closing timing of the exhaust valve 56 is advanced and the opening timing of the intake valve 52 is delayed, so that a negative valve overlap can be caused. A thick curve in FIG. 3 is a valve lift diagram of the intake valve 52 and the exhaust valve 56 when a negative valve overlap is generated. The magnitude (period) of the negative valve overlap can be changed according to the degree to which the closing timing of the exhaust valve 56 and the opening timing of the intake valve 52 are changed.

  When a negative valve overlap is generated, the exhaust valve 56 is closed before the burned gas in the cylinder completely flows out to the exhaust port 22. The burned gas that has not been discharged to the exhaust port 22 remains in the cylinder as it is, or once exits to the intake port 35 when the intake valve 52 is opened, and then the piston 64 descends together with fresh air. Inhaled. When a negative valve overlap occurs, internal EGR can be performed in this way. Hereinafter, the exhaust gas recirculated by the internal EGR is referred to as “internal EGR gas”.

  The magnitude of the negative valve overlap and the internal EGR amount or the internal EGR rate (the ratio of the internal EGR gas in the gas flowing into the cylinder) have a correlation. That is, as the negative valve overlap is increased, the internal EGR amount and the internal EGR rate can be increased. For this reason, in the system of this embodiment, the internal EGR amount and the internal EGR rate can be controlled by adjusting the magnitude of the negative valve overlap.

  In this embodiment, as shown in FIG. 3, the opening timing of the exhaust valve 56 and the closing timing of the intake valve 52 are changed as the magnitude of the negative valve overlap is changed. The magnitude of the negative valve overlap may be changed without changing the opening timing of the exhaust valve 56 and the closing timing of the intake valve 52. In this embodiment, the magnitude of the negative valve overlap is changed by changing both the closing timing of the exhaust valve 56 and the opening timing of the intake valve 52. However, the closing timing of the exhaust valve 56 is changed. The magnitude of the negative valve overlap may be changed by changing either the opening timing of the intake valve 52 or the intake valve 52. In this case, the diesel engine 10 may include only one of the intake variable valve mechanism 54 and the exhaust variable valve mechanism 58. Furthermore, in the present invention, internal EGR is performed by generating a normal valve overlap (positive valve overlap) in which both the intake valve 52 and the exhaust valve 56 are opened, and the magnitude of the positive valve overlap. The internal EGR amount may be adjusted by changing the length.

[Features of Embodiment 1]
As described above, in the diesel engine 10 of the present embodiment, both internal EGR and external EGR can be performed. When EGR is performed, the combustion temperature can be lowered, so that NOx emission can be suppressed.

  In performing the internal EGR and the external EGR, the ratio between the internal EGR amount and the external EGR amount is at least one of the magnitude of the negative valve overlap, the opening degree of the EGR valve 44, and the opening degree of the intake throttle valve 36. It is possible to adjust by changing one. In the following description, the ratio of the internal EGR amount to the total EGR amount, which is the sum of the internal EGR amount and the external EGR amount, is referred to as “internal / external ratio of EGR” or simply “internal / external ratio”. The ratio between the quantity and the external EGR quantity will be expressed using this internal / external ratio. In other words, when the internal / external ratio is zero, the entire EGR is covered by the external EGR, and when the internal / external ratio is 1, the entire EGR is covered by the internal EGR. It will be.

  FIG. 4 is a timing chart for explaining the operation of EGR control in the system of the present embodiment. More specifically, FIG. 4 (A) is a waveform of smoke emission from the diesel engine 10, FIG. 4 (B) is a waveform of the internal / external ratio of EGR, and FIG. 4 (C) is a total. FIG. 4D shows the waveform of the target torque of the diesel engine 10.

  4A to 4C, a waveform indicated by a broken line indicates a waveform of a target value in the EGR control of the comparative example, and a waveform indicated by a one-dot chain line indicates a waveform of an actual value in the EGR control of the comparative example. A waveform indicated by a solid line indicates a waveform characteristic of the EGR control of the present embodiment.

Figure 4 is a vehicle equipped with the diesel engine 10 is, at time t ₀ is traveling on level ground, shows an example in which started climbing from the time t ₂ after some time from time t _0. As shown in FIG. 4D, the target torque (engine load) of the diesel engine 10 is relatively small until time t ₂ when traveling on a flat ground, and increases rapidly from time t ₂ with the start of climbing.

(EGR control of comparative example)
In the following, first, EGR control of a comparative example will be described in order to easily explain the operation and effect of the present embodiment. Time t ₂ during previous level ground traveling, so requires only a quantity of intake air is relatively small, it is possible to put that much EGR gas. That is, the total EGR rate can be made relatively high. On the other hand, when climbing a time t ₂ later, since it requires a lot of the intake air amount, is less afford to add EGR gas. For this reason, it is necessary to reduce the total EGR rate.

  In performing internal EGR and external EGR, it is usually preferable to make the ratio of external EGR relatively large, that is, to make the internal / external ratio relatively low. In the external EGR, exhaust gas that recirculates can be cooled by the EGR cooler 42, whereas in the internal EGR, the exhaust gas recirculates at a high temperature. For this reason, even if the total EGR rate is the same, increasing the ratio of the external EGR can lower the in-cylinder temperature and further reduce the amount of NOx and smoke discharged (see FIG. 13).

For the above reasons, when traveling on a flat ground before time t _2, EGR is performed at a relatively low inside / outside ratio, as shown in FIG. That is, the ratio of the external EGR amount to the total EGR amount is relatively large. From this state, when climbing is started at time t ₂ and the target torque is increased, a request to lower the total EGR rate is generated in order to secure the intake air amount. In order to meet this requirement, control is performed to reduce the internal EGR amount by reducing the negative valve overlap, and to reduce the external EGR amount by closing the EGR valve 44 or opening the intake throttle valve 36. .

In this case, the internal EGR amount decreases rapidly (in one cycle) after the negative valve overlap is reduced. On the other hand, the external EGR amount does not decrease immediately even if the EGR valve 44 or the intake throttle valve 36 is moved. This is because the volume of the external EGR paths such as the external EGR passage 40 and the EGR cooler 42 is large, and therefore, the EGR valve 44 and the intake throttle valve 36 remain in the external EGR path for several cycles after moving. This is because the exhausted gas continues to be mixed into the intake air. For this reason, in the comparative example, the amount of external EGR is reduced only gradually after time t ₂ , so the total EGR rate is reduced only slowly (arrow a in FIG. 4C). For this reason, the total EGR rate immediately after the start of climbing is higher than the target value. As a result, since the oxygen concentration in the cylinder is insufficient as compared with the fuel injection amount increased in accordance with the increase in the engine load accompanying the start of climbing, the smoke emission amount increases rapidly (FIG. 4A). Middle arrow b).

(EGR control of Embodiment 1)
Hereinafter, the EGR control of the first embodiment will be described focusing on differences from the comparative example. In the present embodiment, the following EGR control is performed in order to prevent a sudden increase in smoke emission immediately after the start of climbing as in the comparative example. In the system of the present embodiment, the navigation system 72 can output the current position of the vehicle and road information in the traveling direction of the vehicle. The road information includes information related to the slope. Therefore, according to the information outputted from the navigation system 72, the vehicle is the time that reaches the uphill starting point, that is able to predict the time t ₂ the target torque of the diesel engine 10 (engine load) increases in advance It is. Therefore, in the present embodiment, when it is predicted in advance that the target torque of the diesel engine 10 will increase in the future, the EGR internal / external ratio is increased immediately before the increase actually occurs. did.

That is, as indicated by an arrow c in FIG. 4B, the EGR internal / external ratio is increased from time t ₁ immediately before time t ₂ at which the target torque is expected to increase, and time t ₂ Therefore, control was performed so that the internal / external ratio was a sufficiently high value. According to such control, the state in which most of the total EGR amount is covered by the internal EGR, that is, the state in which the external EGR amount is small, can be made immediately before the target torque increases due to the start of climbing. In such a state, when a request to suddenly reduce the total EGR rate with the start of climbing is made, the total EGR amount can be drastically reduced by reducing the size of the negative valve overlap. The total EGR rate can quickly follow the target value (arrow d in FIG. 4C). As a result, even if the fuel injection amount is increased with the start of climbing, the in-cylinder oxygen concentration is not deficient, and smoke discharge can be effectively suppressed (arrow e in FIG. 4A). ).

  Further, the increase in engine load occurs not only at the start of climbing but also at the initial stage of acceleration of the vehicle. The situation in which the vehicle travels at an accelerated speed is immediately after passing through a traffic jam or after passing through a toll booth such as an expressway. According to the navigation system 72, it is also possible to predict a traffic jam elimination point and a road toll pass time. Further, the acceleration of the vehicle occurs immediately after the start. The start of the vehicle can be predicted in advance by detecting the operation of the driver with respect to the transmission, clutch, and brake. Therefore, in the present embodiment, in these cases, as in the case of starting uphill in FIG. 4, control is performed to increase the EGR internal / external ratio immediately before the engine load increases.

[Specific Processing in Embodiment 1]
FIGS. 5 and 6 are flowcharts of routines executed by the ECU 50 in the present embodiment in order to realize the above functions. According to the routine shown in FIG. 5, it is first determined whether or not it is predicted that the engine load will increase in the near future (step 100). Specifically, the engine load is predicted to increase in the following cases.

1. The navigation system 72 outputs information indicating that there is an uphill road in the traveling direction of the vehicle. This is to predict an increase in engine load at the start of climbing as in the case described with reference to FIG.
2. When the navigation system 72 outputs information that there is a road congestion elimination point in the vehicle traveling direction. This predicts an increase in the engine load accompanying the acceleration of the vehicle immediately after passing through the traffic jam.
3. When the navigation system 72 outputs information that there is a road toll gate in the traveling direction of the vehicle. This predicts an increase in the engine load accompanying the acceleration of the vehicle immediately after passing the road toll gate.
4). When the shift position sensor 66 detects that the transmission has been shifted from neutral to the starting stage (first gear) when the vehicle is stopped. In this case, it can be predicted that the vehicle will start immediately after that. Therefore, it can be predicted that the engine load increases with acceleration immediately after the start.
5). The clutch pedal sensor 68 detects that the clutch pedal has been depressed when the vehicle is stopped. In this case, it can be predicted that the vehicle will start immediately after that. Therefore, it can be predicted that the engine load increases with acceleration immediately after the start.
6). When the brake pedal sensor 70 detects that the brake pedal has been stepped off when the vehicle is stopped. In this case, it can be predicted that the vehicle will start immediately after that. Therefore, it can be predicted that the engine load increases with acceleration immediately after the start.
7). The shift position sensor 66 detects that the transmission has been shifted up or down during acceleration. Whether or not the vehicle is accelerating can be determined based on whether or not the accelerator pedal has been depressed before and after shifting. If the vehicle is upshifted or downshifted during acceleration traveling, it can be predicted that the vehicle will accelerate again immediately thereafter. Therefore, it can be predicted that the engine load increases with the acceleration.

  If none of the above conditions 1 to 7 is established in step 100, an increase in engine load is not predicted. In this case, the determination in step 100 is repeated. On the other hand, when any of the above conditions 1 to 7 is satisfied, an increase in engine load is predicted. In this case, the target internal / external ratio of EGR to be realized immediately before the increase in the engine load is then determined (step 102). This target internal / external ratio is set to a value higher than the target value during normal control corresponding to the current operating state of the diesel engine 10 (see FIG. 4B). Further, as will be described later, this target internal / external ratio may be determined according to the predicted change rate of the engine load. In step 100, an increase in engine load may be predicted according to conditions other than the above conditions 1-7.

When the target in / out ratio of EGR to prepare for an increase in engine load is determined by the processing of the routine shown in FIG. 5, the routine shown in FIG. 6 is performed to realize the target in / out ratio. Is executed. The execution of the routine shown in FIG. 6 is assumed to start at time t ₁ immediately before time t ₂ at which the engine load is predicted to increase.

  In the present embodiment, as described below, feedforward control is performed for the internal EGR, and feedback control is performed for the external EGR.

  According to the routine shown in FIG. 6, first, the valve timings of the intake valve 52 and the exhaust valve 56 are determined based on the target internal EGR rate (step 104). In step 104, the target internal EGR rate can be calculated by multiplying the target total EGR rate determined according to the operating state of the diesel engine 10 by the target in / out ratio determined in step 102. it can. Since the internal EGR rate and the magnitude of the negative valve overlap have a correlation, the magnitude of the negative valve overlap is determined from the target internal EGR rate, and the magnitude of the negative valve overlap is further determined. Therefore, the valve timings of the intake valve 52 and the exhaust valve 56 can be determined.

  As described above, since the target internal / external ratio is set to a higher value than during normal control, the target internal EGR rate in step 104 is also higher than that during normal control. Therefore, the valve timing determined in step 104 is set to a value that causes the negative valve overlap to be larger than that during normal control. When the valve timings of the intake valve 52 and the exhaust valve 56 are determined in this way, the states of the intake variable valve operating device 54 and the exhaust variable valve operating device 58 are controlled so that the valve timing is realized.

  Subsequent to the process of step 104, the target intake air amount is determined based on the target total EGR rate (step 106). In the present embodiment, the external EGR is feedback controlled based on the intake air amount. When the internal EGR and the external EGR are generated, the EGR gas is sucked into the cylinder of the diesel engine 10 instead of a part of the air (fresh air). In other words, when the internal EGR and the external EGR are generated, the amount of air (fresh air) sucked into the cylinder is reduced accordingly. For this reason, the intake air amount has a correlation with the total EGR rate. Therefore, if the target intake air amount corresponding to the target total EGR rate is set and the external EGR amount is adjusted so that the actual intake air amount detected by the air flow meter 38 matches the target intake air amount, The total EGR rate can be matched with the target value.

  Following the processing of step 106, the map values of the opening degrees of the EGR valve 44 and the intake throttle valve 36 are read (step 108). The ECU 50 stores a map that defines the relationship between parameters such as the engine speed, engine load (target torque), intake pressure, target external EGR rate, and the basic opening of the EGR valve 44 and the intake throttle valve 36. Yes. Here, the basic opening degrees of the EGR valve 44 and the intake throttle valve 36 are acquired by referring to the map. Then, the opening degrees of the EGR valve 44 and the intake throttle valve 36 are controlled so that the acquired basic opening degree is realized.

  Subsequently, it is determined whether or not the actual intake air amount detected by the air flow meter 38 matches the target intake air amount determined in step 106 (step 110). If it is determined that the actual intake air amount does not match the target intake air amount, then feedback correction values for the opening degrees of the EGR valve 44 and the intake throttle valve 36 are calculated (step 112). These feedback correction values can be calculated by, for example, PI control, PID control, or the like based on the deviation between the target intake air amount and the actual intake air amount.

  Once the feedback correction value is calculated by the process of step 112, next, the EGR valve 44 and the intake air are adjusted so that the opening degree of the EGR valve 44 and the intake throttle valve 36 becomes the opening degree corrected by the feedback correction value. The throttle valve 36 is controlled (step 114), and then the processing from step 110 onward is executed again. When it is determined that the actual intake air amount matches the target intake air amount, the routine processing shown in FIG. 6 is terminated.

  According to the routine processing shown in FIGS. 5 and 6 described above, it is possible to predict in advance that the engine load will increase due to climbing or acceleration. The EGR internal / external ratio can be increased immediately before the predicted increase in engine load actually occurs (see arrow c in FIG. 4B). For this reason, when an increase in engine load actually occurs and a request is made to suddenly reduce the total EGR rate, the total valve EGR rate is quickly reduced (in one cycle) by reducing the negative valve overlap. (See arrow d in FIG. 4C). Therefore, even when a large amount of fuel is injected as the engine load increases, it is possible to avoid a situation in which the oxygen concentration in the cylinder is insufficient, so that smoke discharge can be effectively suppressed (FIG. 4 ( A) Arrow in e).

  In addition, according to the present invention, it is possible to avoid the control for limiting the fuel injection amount in order to reduce the smoke emission amount immediately after the engine load increases as in the prior art. For this reason, the target torque can be satisfied immediately after the engine load increases, and a sufficient output can be generated. Therefore, excellent drivability can be obtained without sacrificing acceleration.

Also, until just before the engine load increases (until time t _{1 in} FIG. 4), the EGR internal / external ratio is not increased, so that the state in which the ratio of external EGR is large is maintained until then. be able to. As described above, even if the total EGR rate is the same, increasing the ratio of external EGR can lower the in-cylinder temperature, so that the amount of NOx and smoke discharged can be further reduced (see FIG. 13). Therefore, according to the present invention, the amount of NOx and smoke discharged can be further reduced as compared with the case where control is performed such that the internal / external ratio is always increased during light loads.

(Return control to normal control at the time of load increase prediction misjudgment)
As described above, in the present embodiment, an increase in engine load is predicted in advance based on information on road conditions, a driver's operation on a transmission, a clutch, and a brake, and immediately before the engine load increases. In addition, the EGR internal / external ratio is controlled to be higher than that during normal control. In this embodiment, if it is predicted that the engine load will increase and if the engine load does not actually increase at the predicted time, the control will return to normal control and the EGR internal / external ratio will be It was decided to return to the normal value.

FIG. 7 is a flowchart of a routine executed by the ECU 50 in order to realize the above function. According to the routine shown in FIG. 7, the elapsed time after the time when it is determined that the engine load increases based on the prediction made in step 100 is integrated (step 116). That is, in the case of FIG. 4, the elapsed time after time t ₂ is calculated. This elapsed time integration is reset at that point when an increase in engine load actually occurs.

  Subsequently, it is determined whether or not the elapsed time calculated in step 116 has exceeded a predetermined value. If it is determined that the elapsed time does not exceed the predetermined value, the process returns to step 116 and the elapsed time integration process is performed again. On the other hand, if it is determined that the elapsed time has exceeded a predetermined value, it can be determined that the prediction made in step 100 has been wrong. Therefore, in this case, the determination that it is just before the load increases is reset (step 120), and the normal control is restored (step 122).

  According to the processing of the routine shown in FIG. 7 described above, if the prediction that the engine load will increase is off, the EGR internal / external ratio is increased at the time when this is confirmed. Can be released to return to the normal internal / external ratio. Thereby, the ratio of the internal EGR to the total EGR amount decreases and the ratio of the external EGR increases, so that the in-cylinder temperature can be lowered. Therefore, the amount of NOx and smoke discharged can be reduced.

(Setting target / outside ratio according to load change)
When the engine load increases, the amount of increase in the fuel injection amount increases as the degree of increase increases. In order to prevent smoke discharge, it is important to rapidly increase the amount of air in the cylinder by decreasing the EGR amount more quickly as the fuel injection amount increases. The higher the internal / external ratio, the quicker the EGR amount can be rapidly decreased and the in-cylinder air amount can be increased rapidly. From this point of view, it is desirable to increase the internal / external ratio immediately before the increase in engine load as the predicted increase in engine load increases.

  When the increase in engine load is predicted in advance, how much the engine load increases, for example, in the case of climbing, it is determined that the higher the slope of the climbing road, the higher the load is. Is possible. Therefore, in the present embodiment, when setting the target in / out ratio in step 102, the target in / out ratio may be set to a higher value as the predicted degree of increase in engine load is larger. .

  In this case, the target in / out ratio can be set using a map as shown in FIG. FIG. 8 is a diagram showing a map that defines the relationship between the predicted load change rate and the target internal / external ratio. In the map shown in FIG. 8, the degree of increase in engine load is represented by “load change rate”. The “load change rate” is a value obtained by dividing the target torque when the predicted engine load increases by the target torque before the predicted increase in engine load occurs.

  According to the map shown in FIG. 8, the target in / out ratio can be set to a higher value as the predicted load change rate is larger. Further, in the map shown in FIG. 8, the larger the load before the predicted increase in engine load (hereinafter referred to as “base load”) is, the more the curve graph in FIG. / Outer ratio is set to a small value. In a relatively light load area, the in-cylinder temperature rises to some extent by performing a certain amount of internal EGR even in steady operation to prevent the in-cylinder temperature from becoming too low and discharging HC. It is preferable to make it. On the other hand, in a relatively high load region where the in-cylinder temperature tends to be high, it is preferable to mainly perform external EGR capable of cooling the EGR gas without performing internal EGR as much as possible. According to the map shown in FIG. 8, it is possible to set a more appropriate target inside / outside ratio according to the magnitude of the base load in consideration of such a situation.

(Setting of total EGR rate according to internal / external ratio)
As described above, in the present embodiment, the EGR internal / external ratio is increased immediately before the predicted increase in engine load. When the inside / outside ratio is increased, the in-cylinder temperature is increased as described above, and smoke tends to be easily discharged. In the present invention, since the time during which the EGR internal / external ratio is kept high is short (in the case of FIG. 4, only from the time t ₁ to the time t ₂ ), even if the smoke emission amount increases slightly during this time, there is not much problem. It will not be. On the other hand, even if it is the discharge | emission of the smoke of that extent, if it can be suppressed, it will not be over it. Therefore, in the present embodiment, when the internal / external ratio is increased immediately before the engine load increases, control is performed so that the total EGR ratio decreases as the internal / external ratio increases (in FIG. 4C). Arrow f). Thereby, since smoke discharge | emission at the time of raising an inside / outside ratio can be suppressed, the smoke discharge amount as a whole can further be reduced.

  FIG. 9 is a diagram showing a map used when the above-described control is performed, that is, a map that defines the relationship between the inner / outer ratio and the total EGR rate. According to the map shown in FIG. 9, the larger the inner / outer ratio, the smaller the total EGR rate can be set. When increasing the internal / external ratio of EGR immediately before the predicted increase in engine load, control is performed so that the total EGR ratio determined by the map shown in FIG. Thus, the above effect can be exhibited.

  The relationship (slope) between the internal / external ratio and the total EGR rate in the map shown in FIG. 9 is preferably set as follows. FIG. 10 is a diagram showing changes in the in-cylinder oxygen amount when the internal / external ratio is changed with the total EGR rate being constant. The “in-cylinder oxygen amount” refers to the amount of oxygen present in the cylinder at the end of intake, that is, when the intake valve 52 is closed. When the internal / external ratio is increased while keeping the total EGR rate constant, the amount of fresh air drawn into the cylinder decreases as the in-cylinder temperature rises. For this reason, when the internal / external ratio is increased while keeping the total EGR rate constant, the in-cylinder oxygen amount decreases as shown by the thick solid line in FIG. As indicated by a plurality of thin solid lines in FIG. 10, the line having a constant total EGR rate shifts to the upper side in FIG. 10 as the total EGR rate is lower, and the lower side in FIG. 10 as the total EGR rate is higher. Migrate to

  When the in-cylinder oxygen amount decreases, smoke is easily discharged. In other words, if the in-cylinder oxygen amount can be made constant, smoke discharge can be avoided. The broken line in FIG. 10 is a line with a constant in-cylinder oxygen amount. The intersection of this line and a line group with a constant total EGR rate is indicated by a black circle in the figure. In the present embodiment, it is preferable to create a map as shown in FIG. 9 by reading the values of the inner / outer ratio and the total EGR rate at each intersection indicated by these black circles. Accordingly, by determining the total EGR rate according to the map shown in FIG. 9, the in-cylinder oxygen amount can be kept constant, and smoke discharge can be avoided reliably.

  The necessary in-cylinder oxygen amount increases as the fuel injection amount increases, that is, as the load increases. Therefore, it is necessary to shift the broken line in FIG. 10 upward as the load increases. For this reason, as shown in FIG. 9, the graph showing the relationship between the internal / external ratio and the total EGR rate shifts to the lower side in FIG. 9 as the base load becomes higher. Conversely, as the base load becomes lighter, the graph showing the relationship between the inner / outer ratio and the total EGR rate shifts to the upper side in FIG.

  FIG. 11 is a flowchart of a routine executed by the ECU 50 in order to realize the above function. The routine shown in FIG. 11 is executed as a subroutine in step 102 in the routine of FIG. 5 described above. According to the routine shown in FIG. 11, first, the load change rate is predicted (step 124). As described above, the load change rate can be calculated by dividing the predicted target torque when the engine load increases by the target torque before the predicted increase in engine load occurs. The target torque when the engine load increases can be predicted as follows. In the case of uphill, the target torque can be predicted according to the slope of the uphill road. In the case of acceleration, prediction can be made based on information on acceleration conditions (start acceleration or intermediate acceleration, etc.) and information on acceleration points (such as whether a traffic jam is resolved or after passing a toll gate). Further, the driver's acceleration method (加速) may be learned, and the learned content may be reflected to predict the target torque.

  Subsequently, the target in / out ratio is determined based on the load change rate predicted in step 124 and the base load (step 126). Specifically, the target in / out ratio is determined according to the map shown in FIG. The target in / out ratio determined here is used when executing the process of step 104 of the routine shown in FIG.

  Subsequently, the total EGR rate is determined based on the target in / out ratio determined in step 126 and the base load (step 128). Specifically, the total EGR rate is determined according to the map shown in FIG. The map shown in FIG. 9 is created based on the relationship shown in FIG. Therefore, according to the map shown in FIG. 9, the total EGR rate can be determined so that the in-cylinder oxygen amount is kept constant even when the EGR inner / outer ratio increases. The total EGR rate determined here is used when executing the processing of step 106 of the routine shown in FIG. That is, it is used as a target total EGR rate when performing control to increase the internal / external ratio of EGR immediately before the engine load increases.

  In this embodiment, when the routine shown in FIG. 11 is performed, the following advantages are obtained. As a first advantage, the larger the predicted increase in engine load, the higher the internal / external ratio immediately before the engine load increases. For this reason, the NOx emission amount can be effectively suppressed until the time when the engine load increases, and the total EGR rate can be increased more quickly when the engine load increases to a large extent and the fuel injection amount increases significantly. The oxygen concentration in the cylinder can be rapidly increased by lowering. Therefore, even when the fuel injection amount is significantly increased with the start of steep climbing or sudden acceleration, smoke discharge can be effectively suppressed.

  As a second advantage, when the EGR internal / external ratio is increased immediately before the engine load increases, the total EGR rate can be lowered as the target internal / external ratio increases. For this reason, it is possible to avoid an increase in smoke discharge amount due to an increase in the in-cylinder temperature due to an increase in the internal / external ratio. In particular, according to the routine processing shown in FIG. 11, the total EGR rate can be determined so that the in-cylinder oxygen amount is kept constant even when the EGR inner / outer ratio increases. For this reason, since it is possible to reliably prevent the in-cylinder oxygen amount from being insufficient when the internal / external ratio is increased, it is possible to more reliably suppress the discharge of smoke.

  In the above description, the total EGR rate is controlled so that the in-cylinder oxygen amount remains constant regardless of the increase in the EGR internal / external ratio. However, instead of the in-cylinder oxygen amount, The oxygen concentration may be controlled to be constant.

(Setting the start time of the change in internal / external ratio)
It takes some time to increase the EGR internal / external ratio immediately before the expected increase in engine load. That is, there is a limit to the slope of the portion indicated by the arrow c in FIG. This is because, as described above, since the volume of the external EGR path is large, it takes time to change (decrease) the external EGR amount.

Therefore, when the EGR internal / external ratio is changed, the time required for the internal / external ratio to reach the target value increases as the degree of change increases. In view of this, when changing the internal / external ratio of EGR immediately before the predicted engine load change, the change start time (time t _{1 in} the case of FIG. 4) is earlier as the degree of change is larger. It is preferable to do.

  FIG. 12 is a flowchart of a routine executed by the ECU 50 in order to satisfy the above request. The routine shown in FIG. 12 is assumed to be executed after execution of the routine shown in FIG.

  According to the routine shown in FIG. 12, first, the rate of change of the internal / external ratio of EGR is determined (step 130). Specifically, the value obtained by dividing the target internal / external ratio determined in step 102 of the routine of FIG. 5 by the current internal / external ratio (internal / external ratio during normal control) is the internal / external ratio. It is determined as the rate of change.

Next, the change start time of the internal / external ratio (time t _{1 in} the case of FIG. 4) is determined (step 132). Here, in accordance with the change rate of the internal / external ratio determined in step 130, the change start time of the internal / external ratio is set to be earlier as the change rate is larger.

  Subsequently, it is determined whether or not the change start time determined in step 132 has arrived (step 134). If it is determined that the change start time has arrived, the internal / external ratio is set to the target value. Control to be changed, that is, execution of the routine shown in FIG. 6 is started (step 136).

  When the routine shown in FIG. 12 described above is executed, even if the rate of change of the internal / external ratio is large and it takes a relatively long time to match the internal / external ratio to the target value, The internal / external ratio can be reliably matched to the target value before the predicted change in engine load occurs.

Further, when the rate of change of the inside / outside ratio is small, the change start time can be delayed. For this reason, the time required to increase the internal / external ratio immediately before the engine load increases (in the case of FIG. 4, from time t ₁ to t ₂ ) can be minimized. That is, it is possible to minimize the time during which the exhaust amount of NOx and smoke tends to increase due to an increase in the in-cylinder temperature caused by the increase in the internal / external ratio.

  In the first embodiment described above, the case where the predicted change in the engine load is in the direction in which the engine load increases has been described, but the present invention shows that the change in the predicted engine load decreases the engine load. It is also possible to apply to an apparatus that controls the EGR internal / external ratio accordingly just before the engine load decreases.

  In the first embodiment described above, the external EGR passage 40 and the EGR cooler 42 are the “external EGR means” in the first invention, and the intake variable valve mechanism 54 and the exhaust variable valve mechanism 58 are the first. In the “internal EGR means” of the present invention, the intake throttle valve 36, the EGR valve 44, the intake variable valve mechanism 54 and the exhaust variable valve mechanism 58 are respectively included in the “internal / external ratio adjusting means” of the first invention. It corresponds. Further, when the ECU 50 executes the process of step 100, the “load change predicting means” in the first aspect of the invention executes the process of step 102, and the “target value setting means of the first aspect of the invention”. "Internal / external ratio control means" according to the first aspect of the present invention is realized by executing the processing of the routine shown in FIG.

  In the first embodiment described above, the ECU 50 executes the processes of steps 124 and 126 described above, and the “means for setting a target value” in the third invention is shown in step 128 and FIG. By executing the routine processing, the “total EGR rate control means” in the fifth invention and the “cylinder oxygen stabilization control means” in the sixth invention execute the routine processing shown in FIG. Thus, the “internal / external ratio change start timing setting means” according to the seventh aspect of the present invention is realized.

  Further, in the first embodiment described above, the navigation system 72 is the “road information output means” in the eighth invention, and the shift position sensor 66, the clutch pedal sensor 68 and the brake pedal sensor 70 are in the ninth invention. Each corresponds to “detection means”. Further, when the ECU 50 executes the processing of step 100, the “predicting means” in the eighth and ninth inventions executes the processing of the routine shown in FIG. The “inside / outside ratio restoring means” is realized.

It is a figure for demonstrating the system configuration | structure of Embodiment 1 of this invention. It is a figure which shows the cross section of one cylinder of the diesel engine in the system shown in FIG. It is a figure for demonstrating a negative valve overlap. It is a timing chart for demonstrating the operation | movement of EGR control in the system of Embodiment 1 of this invention. It is a flowchart of the routine performed in Embodiment 1 of the present invention. It is a flowchart of the routine performed in Embodiment 1 of the present invention. It is a flowchart of the routine performed in Embodiment 1 of the present invention. It is a figure which shows the map which defined the relationship between the change rate of the load estimated, and the target internal / external ratio. It is a figure which shows the map which defined the relationship between an inside / outside ratio and a total EGR rate. It is a figure which shows the change of the in-cylinder oxygen amount at the time of changing an internal / external ratio by making a total EGR rate constant. It is a flowchart of the routine performed in Embodiment 1 of the present invention. It is a flowchart of the routine performed in Embodiment 1 of the present invention. It is a figure which shows the relationship between the combustion area | region of diesel, a soot (Soot) production | generation area | region, and a NOx production | generation area | region.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Diesel engine 12 Injector 14 Common rail 18 Exhaust passage 20 Exhaust manifold 22 Exhaust port 24 Turbo supercharger 26 Exhaust purification device 28 Intake passage 34 Intake manifold 36 Intake throttle valve 38 Air flow meter 40 External EGR passage 44 EGR valve 46 Intake pressure sensor 50 ECU
52 Intake valve 54 Intake variable valve mechanism 56 Exhaust valve 58 Exhaust variable valve mechanism 62 Crank angle sensor 64 Piston

Claims (11)

An external EGR means for recirculating exhaust gas through an external EGR passage connecting the exhaust passage and the intake passage of the internal combustion engine;
Internal EGR means for generating EGR inside the internal combustion engine without passing through the external EGR passage;
An internal / external ratio adjusting means for adjusting a ratio between the internal EGR amount and the external EGR amount;
Load change prediction means for predicting changes in engine load in advance;
A target value setting means for setting a target value of a ratio between the internal EGR amount and the external EGR amount in order to prepare for the engine load change according to the predicted change in the engine load;
An internal / external ratio control means for controlling the internal / external ratio adjusting means so that the ratio between the internal EGR amount and the external EGR amount becomes the target value immediately before the predicted change in engine load actually occurs. ,
A control device for an internal combustion engine, comprising:   2. The target value is a value such that a ratio of an internal EGR amount to a total EGR amount is higher than that during normal operation when an increase in engine load is predicted. The internal combustion engine control device described.   The control apparatus for an internal combustion engine according to claim 1 or 2, wherein the target value setting means includes means for setting the target value in accordance with the predicted degree of change in engine load.   When an increase in engine load is predicted, the target value is a value such that the greater the degree of increase in engine load, the higher the ratio of the internal EGR amount to the total EGR amount. The control apparatus for an internal combustion engine according to any one of claims 1 to 3.   When control is performed so that the ratio between the internal EGR amount and the external EGR amount becomes the target value immediately before the predicted change in engine load actually occurs, the ratio of the internal EGR amount to the total EGR amount is high. 5. The control apparatus for an internal combustion engine according to claim 1, further comprising total EGR rate control means for controlling the total EGR rate so that the total EGR rate decreases.   When control is performed so that the ratio between the internal EGR amount and the external EGR amount becomes the target value immediately before the predicted change in engine load actually occurs, the amount of oxygen in the cylinder when the intake valve is closed or 6. The internal combustion engine according to claim 1, further comprising in-cylinder oxygen stabilization means for controlling the total EGR rate so that the oxygen concentration is substantially constant before and after the control. Control device.   When the ratio between the internal EGR amount and the external EGR amount is controlled to be the target value immediately before the predicted change in engine load actually occurs, the greater the degree of change in the ratio, the more 7. The control device for an internal combustion engine according to claim 1, further comprising an internal / external ratio change start timing setting means for accelerating a time point at which the ratio starts to change. The load change prediction means includes
Road information output means for outputting road information in the traveling direction of the vehicle;
Based on the road information, means for predicting that a change in engine load will occur when passing at least one of a slope, a congestion elimination point, and a road toll gate;
The control apparatus for an internal combustion engine according to claim 1, comprising: The load change prediction means includes
Detecting means for detecting a driver's operation on at least one of a transmission, a clutch, and a brake of the vehicle;
Means for predicting a change in engine load based on the detected operation;
The control apparatus for an internal combustion engine according to any one of claims 1 to 8, wherein   The load change prediction means, when the shift position of the transmission is shifted from neutral to the start stage when the vehicle is stopped, when the clutch pedal is depressed when the vehicle is stopped, when the brake pedal is released when the vehicle is stopped, The engine load is predicted to increase immediately after at least one of a case where the transmission is shifted up during acceleration traveling and a case where the transmission is shifted down during acceleration traveling. Item 10. A control device for an internal combustion engine according to Item 9.   The internal / external ratio adjusting means controls the internal / external ratio adjusting means so that the ratio between the internal EGR amount and the external EGR amount is returned to the normal operation ratio when the predicted change in engine load does not actually occur. The control apparatus for an internal combustion engine according to any one of claims 1 to 10, further comprising external ratio restoring means.

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