JP2009047010A - Control device for internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a control device for an internal combustion engine capable of reducing THC and NOx in a high rotation region of the medium-high load of an internal combustion engine in a control device for an internal combustion engine equipped with a supercharger. <P>SOLUTION: This device is provided with a turbo supercharger 24 disposed in an intake passage 28 of the internal combustion engine, a first intake throttle valve 36 arranged in the upstream side of the turbo supercharger 24 in the intake passage 28, and a second intake throttle valve 38 arranged in the downstream side of the turbo supercharger 24 in the intake passage 28. In the medium-high load region of the internal combustion engine, when it is determined that engine speed is in the high rotation region equal to or higher than a prescribed value, an intake air amount is controlled mainly by using the first intake throttle valve 36. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an internal combustion engine control device, and more particularly to an internal combustion engine control device including a supercharger.

  Conventionally, as disclosed in, for example, Japanese Patent Laid-Open No. 10-299524, an intake device for a supercharged engine in which a throttle valve is provided on each of an upstream side and a downstream side of a mechanical supercharger in an intake passage. Proposed. In this device, the pressure difference between the upstream side and the downstream side of the supercharger is reduced by controlling these two throttle valves according to the engine load. Specifically, a bypass passage that bypasses the upstream side and downstream side of the mechanical supercharger in the intake passage is provided, and in the low load region of the engine, the bypass passage is communicated and compared to the upstream throttle valve. The downstream throttle valve is controlled to have a large opening. In a high engine load range, the bypass passage is closed, and the downstream throttle valve has a smaller opening than the upstream throttle valve. To be controlled. Thereby, the differential pressure between the upstream side and the downstream side of the supercharger can be reduced, and the durability of the supercharger can be improved and the fuel efficiency performance of the engine can be improved.

Japanese Patent Laid-Open No. 10-299524 Japanese Patent Laid-Open No. 10-299525 JP 2000-97017 A

  However, in the conventional system, it is difficult to ensure a desired high supercharging pressure in a high rotation range. In other words, in the above conventional system, since the opening degree of the throttle valve downstream of the supercharger is controlled to be small in the high engine load range, the air supercharged in the supercharger is depressurized in the downstream throttle valve. Will be. For this reason, there is a possibility that misfire or an increase in THC discharge amount may be caused due to insufficient air amount in the cylinder or a reduction in the compression ratio.

  The present invention has been made to solve the above-described problems, and provides a control device for an internal combustion engine capable of reducing THC and NOx in a medium and high load, high rotation region of the internal combustion engine. Objective.

In order to achieve the above object, a first invention is a control device for an internal combustion engine,
A supercharger provided in the intake passage of the internal combustion engine;
A first throttle valve disposed upstream of the supercharger in the intake passage;
A second throttle valve disposed downstream of the supercharger in the intake passage;
Control means for controlling the amount of intake air by adjusting the opening of the first throttle valve and / or the second throttle valve;
A determination means for determining whether or not the engine speed is in a high rotation range where the engine speed is equal to or higher than a predetermined value in a medium to high load range of the internal combustion engine
The control means includes
The intake air amount is controlled mainly by using the first throttle valve when it is determined that the vehicle is in the high rotation region.

According to a second invention, in the first invention,
The control means includes
The second throttle valve is fully opened when it is determined that the rotation speed is in the high rotation range.

According to a third invention, in the first or second invention,
An EGR passage that connects a downstream side of the first throttle valve and an upstream side of the supercharger and an exhaust passage of the internal combustion engine in the intake passage;
An external EGR amount varying means for varying the amount of external EGR flowing back through the EGR passage;
An external EGR amount control means for controlling the external EGR amount variable means so as to increase the external EGR amount when it is determined to be in the high rotation region;
Is further provided.

A fourth invention is any one of the first to third inventions,
An internal EGR amount variable means for changing the internal EGR amount by changing the valve overlap of the intake valve and the exhaust valve;
An internal EGR amount control means for controlling the internal EGR amount variable means so that the internal EGR amount increases when it is determined that the engine is in the high rotation region;
Is further provided.

According to a fifth invention, in any one of the first to fourth inventions,
The supercharger is a variable nozzle supercharger capable of adjusting the supercharging pressure,
The supercharging pressure control means for restricting the variable nozzle so as to increase the supercharging pressure when it is determined to be in the high rotation region, further comprising a supercharging pressure control means. Control device for internal combustion engine.

  If the second throttle valve on the downstream side of the supercharger is throttled in the high speed region of the internal combustion engine in which the supercharger is driven, the intake pressure to the internal combustion engine is reduced. According to the first aspect of the present invention, when the engine speed in the medium and high load operation region of the internal combustion engine is in a high rotation region where the value is equal to or higher than a predetermined value, the suction is performed using the first throttle valve upstream of the supercharger. The amount of air is controlled. Therefore, according to the present invention, it is possible to avoid a situation in which the supercharging pressure is limited in the high rotation region and to increase the compression pressure, so that it is possible to effectively suppress the increase in the THC emission amount and the occurrence of misfire. Can do.

  According to the second invention, the second throttle valve on the downstream side of the supercharger is fully opened when the engine speed of the internal combustion engine is in a high rotation region where the engine speed is equal to or greater than a predetermined value. The situation in which the supercharging pressure is limited in can be effectively avoided.

  According to the third aspect of the invention, the amount of external EGR introduced through the EGR passage is increased in the high speed region of the internal combustion engine. The EGR passage connects the exhaust passage and the upstream side of the supercharger and the downstream side of the first throttle valve in the intake passage. For this reason, according to the present invention, since EGR is introduced upstream of the supercharger, it is possible to effectively increase the EGR amount by using the supercharging pressure, effectively increasing the NOx emission amount. Can be suppressed.

  According to the fourth aspect of the invention, the valve overlap can be increased by varying the valve timing in the high rotation region of the internal combustion engine. Therefore, according to the present invention, it is possible to effectively suppress the increase in the NOx emission amount by increasing the internal EGR amount.

  According to the fifth aspect of the present invention, a variable nozzle type supercharger capable of adjusting the supercharging pressure by changing the opening degree of the variable nozzle is used as the supercharger. For this reason, according to the present invention, it is possible to increase the supercharging pressure in the high rotation region of the internal combustion engine, and therefore it is possible to effectively suppress the increase in the THC emission amount and the occurrence of misfire.

  Several 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. The present invention is not limited to the following embodiments.

Embodiment 1 FIG.
[Configuration of Embodiment 1]
FIG. 1 is a diagram for explaining a schematic configuration of an internal combustion engine system as a first embodiment of the present invention. As shown in FIG. 1, the system of the present embodiment includes a four-cycle diesel engine 10 having a plurality of cylinders (four cylinders in FIG. 1). It is assumed that the diesel engine 10 is mounted on a vehicle and used as a power source.

  Each cylinder of the diesel engine 10 is provided with an injector 12 for directly injecting fuel 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 (not shown) of each cylinder. The exhaust passage 18 is connected to the exhaust turbine of the turbocharger 24. A post-treatment device 26 for purifying exhaust gas is provided downstream of the turbocharger 24 in the exhaust passage 18. As the post-processing device 26, for example, an oxidation catalyst, a NOx catalyst, a DPF (Diesel Particulate Filter), a DPNR (Diesel Particulate-NOx-Reduction system), or the like 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 an intake manifold 34 to intake ports (not shown) of each cylinder.

  A first intake throttle valve 36 is provided between the air cleaner 30 and the turbocharger 24 in the intake passage 28. A second intake throttle valve 38 is installed between the intercooler 32 and the intake manifold 34 in the intake passage 28. An air flow meter 72 for detecting the amount of intake air is installed in the intake passage 28 near the downstream of the air cleaner 30.

  One end of an HPL (High Pressure Loop) -EGR passage 40 is connected to the vicinity of the intake manifold 34 in the intake passage 28. The other end of the HPL-EGR passage 40 is connected to the vicinity of the exhaust manifold 20 in the exhaust passage 18. In the present system, external EGR (hereinafter referred to as “HPL-EGR”) for returning a part of the exhaust gas (burned gas) to the intake passage 28 through the HPL-EGR passage 40 can be performed. Hereinafter, the exhaust gas recirculated to the intake passage 28 through the HPL-EGR passage 40 is referred to as “HPL-EGR gas”.

  An HPL-EGR cooler 42 for cooling the HPL-EGR gas is provided in the middle of the HPL-EGR passage 40. An HPL-EGR valve 44 is provided downstream of the HPL-EGR cooler 42 in the HPL-EGR passage 40. By changing the opening of the HPL-EGR valve 44, the amount of exhaust gas passing through the HPL-EGR passage 40, that is, the amount of HPL-EGR can be adjusted. In the present embodiment, the HPL-EGR cooler 42 is provided. However, when the high-temperature exhaust gas is recirculated, the HPL-EGR cooler 42 may not be provided.

  Further, one end of an LPL (Low Pressure Loop) -EGR passage 46 is connected to the upstream side of the turbocharger 24 in the intake passage 28. The other end of the LPL-EGR passage 46 is connected to the vicinity of the downstream side of the aftertreatment device 26 in the exhaust passage 18. In this system, an external EGR that recirculates a part of exhaust gas (burned gas) to the intake passage 28 upstream of the turbocharger 24 through the LPL-EGR passage 46 (hereinafter referred to as “LPL-EGR”). It can be performed. Hereinafter, the exhaust gas recirculated to the intake passage 28 through the LPL-EGR passage 46 is referred to as “LPL-EGR gas”.

  An LPL-EGR cooler 48 for cooling the LPL-EGR gas is provided in the middle of the LPL-EGR passage 46. An LPL-EGR valve 50 is provided downstream of the LPL-EGR cooler 48 in the LPL-EGR passage 46. By changing the opening degree of the LPL-EGR valve 50, the amount of exhaust gas passing through the LPL-EGR passage 46, that is, the LPL-EGR amount can be adjusted.

  An exhaust throttle valve 52 is provided in the vicinity of the downstream side of the connection portion between the exhaust passage 18 and the LPL-EGR passage 46. An intake pressure sensor 74 for detecting the intake pressure is installed downstream of the second intake throttle valve 38 in the intake passage 28. Further, a back pressure sensor 76 for detecting a back pressure is installed upstream of the turbocharger 24 in the exhaust passage 18. Further, the present system is provided with an accelerator opening sensor 78 for detecting the amount of depression of the accelerator pedal (accelerator opening).

  The system of the present embodiment includes an ECU (Electronic Control Unit) 70 as shown in FIG. In addition to the air flow meter 72, the intake pressure sensor 74, the back pressure sensor 76, and the accelerator opening sensor 78 described above, various sensors for controlling the diesel engine 10 are connected to the input portion of the ECU 70. In addition, the output portion of the ECU 70 includes the above-described injector 12, first intake throttle valve 36, second intake throttle valve 38, exhaust throttle valve 52, HPL-EGR valve 44, LPL-EGR valve 50, and diesel engine 10. Various actuators for controlling are connected. The ECU 70 drives each device in accordance with a predetermined program based on various types of input information.

  FIG. 2 is a view showing a cross section of one cylinder of the diesel engine 10 shown in FIG. Hereinafter, the diesel engine 10 will be described in more detail. As shown in FIG. 2, a crank angle sensor 80 for detecting 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 80 is connected to the ECU 70. The crank angle sensor 80 can detect the engine speed.

  Further, the diesel engine 10 includes an intake variable valve mechanism 64 that continuously varies the valve timing (opening / closing timing) of the intake valve 62, and an exhaust variable valve mechanism that continuously varies the valve timing of the exhaust valve 66. 68. These intake variable valve mechanism 64 and exhaust variable valve mechanism 68 are each connected to an ECU 70.

  The specific configurations of the intake variable valve mechanism 64 and the exhaust variable valve mechanism 68 are not particularly limited, and may use a mechanical mechanism such as a cam mechanism, and can be opened and closed at any time. An electromagnetic drive valve or a hydraulic drive valve may be used.

[Operation of Embodiment 1]
(Control of HPL-EGR)
HPL-EGR is performed by returning a part of the exhaust gas (burned gas) to the intake passage 28 through the HPL-EGR passage 40. More specifically, the opening degree of the HPL-EGR valve 44 is adjusted according to the operating state of the diesel engine 10, and the exhaust gas is introduced into the HPL-EGR passage 40. The introduced exhaust gas is cooled in the HPL-EGR cooler 42 and then returned to the intake passage 28.

  Further, the HPL-EGR amount can be adjusted not only by the opening degree of the HPL-EGR valve 44 but also by the opening degree of the second intake throttle valve 38. When the opening of the second intake throttle valve 38 is reduced and the intake air is throttled, the intake pressure decreases, so that the differential pressure from the back pressure (exhaust pressure) increases. That is, the differential pressure across the HPL-EGR passage 40 increases. Thereby, the amount of HPL-EGR can be increased effectively.

(Control of LPL-EGR)
The LPL-EGR is performed by returning a part of the exhaust gas (burned gas) to the upstream side of the turbocharger 24 in the intake passage 28 through the LPL-EGR passage 46. More specifically, the opening degree of the LPL-EGR valve 50 is adjusted according to the operating state of the diesel engine 10, and the exhaust gas is introduced into the LPL-EGR passage 46. The introduced exhaust gas is cooled in the LPL-EGR cooler 48 and then returned to the intake passage 28.

  Further, the LPL-EGR amount can be adjusted not only by the opening degree of the LPL-EGR valve 50 but also by the opening degrees of the first intake throttle valve 36 and the exhaust throttle valve 52. When the opening of the first intake throttle valve 36 is reduced to throttle the intake air, the intake pressure in the vicinity of the connection portion between the intake passage 28 and the LPL-EGR passage 46 is reduced due to the driving of the turbocharger 24. On the other hand, when the opening of the exhaust throttle valve 52 is reduced to restrict the exhaust, the exhaust pressure in the vicinity of the connection portion of the exhaust passage 18 with the LPL-EGR passage 46 increases. Thereby, since the differential pressure before and behind the LPL-EGR passage 46 can be increased, the amount of LPL-EGR can be effectively increased.

(EGR control according to operating conditions)
The appropriate amount of EGR varies depending on operating conditions such as engine speed and load. Specifically, if the amount of EGR is too small, the purpose of EGR such as NOx reduction cannot be achieved. On the other hand, if the amount of EGR is too large, the amount of smoke and THC (hydrocarbon) emissions due to the decrease in oxygen concentration Will increase. For this reason, in EGR control, it is required to control the EGR amount with high accuracy.

  Here, as described above, the system of the present embodiment includes two external EGR systems, that is, LPL-EGR and LPL-EGR. And in these EGR, the driving | operation area | region which can perform EGR efficiently differs, respectively. Therefore, in the system of the present embodiment, these EGRs are properly used based on the operating conditions of the diesel engine 10.

  FIG. 3 is a diagram showing the relationship between the operating range of the diesel engine 10 and the EGR to be performed. As shown in this figure, EGR that can be efficiently executed is determined based on the engine speed and the load. Specifically, HPL-EGR is performed in a relatively low load region. This is because in the low load region, since the intake pressure and the back pressure are both low, a differential pressure sufficient to efficiently perform LPL-EGR does not occur. Hereinafter, a low load region where HPL-EGR is performed is referred to as an “HPL region”.

  Further, as shown in FIG. 3, LPL-EGR can be performed when the operation range of the diesel engine 10 is an intermediate load range greater than the load in the HPL range. This is because the intake pressure and the back pressure rise to some extent by driving the turbocharger 24, and the differential pressure across the LPL-EGR passage 46 increases to such an extent that LPL-EGR can be performed. Further, even in the intermediate load region, HPL-EGR can be performed as long as the engine speed is relatively small. For this reason, HPL-EGR and LPL-EGR are performed in a predetermined low-speed region in the medium load region. Hereinafter, the medium load low rotation region where HPL-EGR and LPL-EGR are performed is referred to as an “HPL + LPL region”.

  Further, LPL-EGR is performed in a region where the engine speed in the medium load region is relatively large. This is because in the predetermined high rotation region in the middle load region, the differential pressure across the HPL-EGR passage 40 decreases due to the increase in the supercharging pressure, so that a differential pressure sufficient to efficiently execute HPL-EGR does not occur. Hereinafter, the medium load high rotation region where the LPL-EGR is performed is referred to as an “LPL region”.

[Characteristic Operation of First Embodiment]
As described above, in the system according to the present embodiment, the diesel engine 10 is controlled by controlling the opening degree of the second intake throttle valve 38 installed between the intercooler 32 and the intake manifold 34 in the intake passage 28. The amount of air taken in can be controlled. Specifically, when the operation region of the diesel engine 10 is the HPL region or the HPL + LPL region, intake air amount (Ga) control using the second intake throttle valve 38 is performed.

  On the other hand, when the operation region of the diesel engine 10 is the LPL region, the supercharging pressure is high. For this reason, if the intake air amount control by the second intake throttle valve 38 is performed, a desired supercharging pressure cannot be secured, which may cause an increase in THC emission amount and occurrence of misfire.

  Therefore, in the present embodiment, the intake air amount is controlled from the upstream side of the turbocharger 24 when the operation region of the diesel engine 10 is the LPL region. A first intake throttle valve 36 is provided between the air cleaner 30 and the turbocharger 24 in the intake passage 28. Therefore, in the LPL region, the intake air amount is controlled by using the first intake throttle valve 36 with the second intake throttle valve fully opened. That is, if the air amount (oxygen amount) is adjusted by controlling the first intake throttle valve 36 and the air necessary for supercharging is supplemented from the LPL-EGR, the air is secured while maintaining a desired supercharging pressure. The amount (oxygen amount) can be accurately controlled. As a result, the in-cylinder pressure can be increased while ensuring a desired oxygen concentration, so that an increase in THC and the occurrence of misfire can be effectively suppressed. Moreover, since LGR-EGR can introduce a large amount of EGR gas even in a region where the supercharging pressure is high, NOx emission can be effectively suppressed.

  Note that the intake air amount control by the first intake throttle valve 36 is less responsive to the change in the intake air amount due to the opening change than that by the first intake throttle valve 36. For this reason, the intake air amount control by the first intake throttle valve 36 is performed only in a high rotation region where a desired boost pressure cannot be secured by the intake air amount control by the second intake throttle valve.

[Specific Processing in Embodiment 1]
Next, with reference to FIG. 4, the specific content of the process performed in this Embodiment is demonstrated. FIG. 4 is a flowchart of a routine in which the ECU 70 executes intake air amount control.

  In the routine shown in FIG. 4, first, the operating conditions in the diesel engine 10 are read (step 100). Specifically, the detection signal of the accelerator opening sensor 78, the detection signal of the crank angle sensor 80, and the like are read here.

  Next, it is determined whether or not the operation region of the diesel engine 10 is the LPL region (step 102). Specifically, the engine speed and the engine load are calculated based on the operating conditions read in step 100 above. The ECU 70 stores a map (see FIG. 3) that defines the engine speed and the engine load, and the operation region sorted by the type of EGR to be executed. Here, based on such a map, an operation region corresponding to the calculated engine speed and engine load is specified. Then, it is determined whether or not the specified operation region is the LPL region.

  If it is determined in step 102 that the current operation region is not the LPL region, that is, if it is determined that the operation region is the HPL region or the HPL + LPL region, the process proceeds to the next step, and the second intake air Intake air amount control using the throttle valve 38 is executed (step 104).

  On the other hand, if it is determined in step 102 that the current operation region is the LPL region, the process proceeds to the next step, and intake air amount control using the first intake throttle valve 36 is executed (step). 106). Specifically, the intake air amount control is executed by the first intake throttle valve 36 after the second intake throttle valve 38 is fully opened. In addition, LPL-EGR is introduced to secure a desired supercharging pressure.

  As described above, according to the system of the first embodiment, in the LPL region, which is a high rotation region with a medium load, by controlling the first intake throttle valve 36, the amount of air is secured while ensuring the supercharging pressure. It can be controlled with high accuracy. Thereby, increase of THC discharge | emission amount and generation | occurrence | production of misfire can be suppressed effectively. Moreover, since LPL-EGR is introduced in order to ensure the supercharging pressure, an increase in the NOx emission amount can be effectively suppressed.

  Incidentally, in the first embodiment described above, when the operating range of the diesel engine 10 is the LPL region, the intake air amount control is performed by the first intake throttle valve 36. The region for controlling the valve 36 is not limited to the LPL region. That is, the HPL + LPL region may be used as long as it is a region where a high supercharging pressure is required, that is, a high rotation region with a medium to high load.

  In the first embodiment described above, the second intake throttle valve 38 is opened fully in the LPL region. However, the opening degree of the second intake throttle valve 38 is not always fully opened. That is, if the intake air amount is controlled mainly by controlling the opening of the first throttle valve, the opening of the second intake throttle valve 38 is also adjusted within a range not limiting the supercharging pressure. Also good.

  In the first embodiment described above, the case where the present invention is applied to control of a diesel engine (compression ignition internal combustion engine) 10 has been described. However, the present invention is not limited to a diesel engine, but a gasoline engine (spark ignition internal combustion engine). Engine) and other various internal combustion engines.

  In the first embodiment described above, the first intake throttle valve 36 is the “first throttle valve” in the first invention, and the second intake throttle valve 38 is the “first throttle valve” in the first invention. It corresponds to “2 throttling valves”. Further, when the ECU 70 executes the process of step 102, the “determination means” in the first invention executes the process of step 106, so that the “control means” in the first invention changes. , Each has been realized.

  In the first embodiment described above, the LPL-EGR passage 46 corresponds to the “EGR passage” in the third aspect of the invention. Further, the “external EGR amount control means” in the third aspect of the present invention is realized by the ECU 70 executing the processing of step 106 described above.

Embodiment 2. FIG.
[Features of Embodiment 2]
Next, a second embodiment of the present invention will be described with reference to FIG. In the present embodiment, a variable nozzle (Variable Nozzle) type turbocharger is used as the turbocharger 24 in the hardware configuration shown in FIG. 1, and the ECU 70 executes a routine shown in FIG. Can be realized. In the description of the present embodiment, the difference from the above-described first embodiment will be mainly described, and the description of the same matters will be simplified or omitted.

  The turbocharger 24 includes a variable nozzle mechanism (not shown). The variable nozzle mechanism has a nozzle whose opening degree can be adjusted (hereinafter referred to as “variable nozzle” or “VN”), and a drive mechanism that changes the opening degree of the variable nozzle by, for example, electric drive. According to this variable nozzle mechanism, the supercharging pressure can be controlled by adjusting the opening of the variable nozzle. That is, if the opening of the variable nozzle is reduced, the inlet area of the exhaust turbine is reduced, and the flow rate of the exhaust gas flowing into the exhaust turbine is increased. As a result, the turbo rotation speed increases and the supercharging pressure can be increased. Conversely, when the opening of the variable nozzle is increased, the inlet area of the exhaust turbine increases, and the flow rate of the exhaust gas flowing into the exhaust turbine decreases. As a result, the turbo rotation speed decreases and the supercharging pressure decreases. Hereinafter, the opening degree of the variable nozzle is referred to as “VN opening degree”.

  In the second embodiment using such a system including the turbocharger 24, when the intake air amount is controlled by the first throttle valve 36 in the first embodiment described above, VN opening is performed. We will narrow down the degree. As a result, it is possible to effectively increase the supercharging pressure in the LPL region, that is, the high rotation region with medium and high loads, and to introduce a large amount of LPL-EGR. it can.

[Specific Processing in Second Embodiment]
Next, with reference to FIG. 5, the specific content of the process performed in this Embodiment is demonstrated. FIG. 5 is a flowchart of a routine in which the ECU 70 executes intake air amount control.

  In the routine shown in FIG. 5, first, the operating conditions in the diesel engine 10 are read (step 200). Next, it is determined whether or not the operation region of the diesel engine 10 is the LPL region (step 202). Here, specifically, the same processing as steps 100 and 102 shown in FIG. 4 is executed.

  When it is determined in step 202 that the current operation region is not the LPL region, that is, when it is determined that the operation region is the HPL region or the HPL + LPL region, the process proceeds to the next step, and the second intake air Intake air amount control using the throttle valve 38 is executed (step 204).

  On the other hand, when it is determined in step 202 that the current operation region is the LPL region, the process proceeds to the next step, and intake air amount control using the first intake throttle valve 36 is executed (step). 206). At the same time, the throttle operation of the VN opening is executed (step 208). Here, specifically, the opening degree of the variable nozzle of the turbocharger 24 is reduced. Further, the LPL-EGR is increased as the supercharging pressure increases.

  As described above, according to the system of the second embodiment, the supercharging pressure is effectively increased by reducing the VN opening of the turbocharger 24 in the LPL region, which is a high rotation region with medium and high loads. Can be made. Thereby, since a large amount of LPL-EGR can be introduced, an increase in the NOx emission amount can be effectively suppressed.

  By the way, in Embodiment 2 mentioned above, when the operation area | region of the diesel engine 10 turns into an LPL area | region, it is supposed that the VN opening degree of the turbocharger 24 will be restrict | squeezed, but the area | region which restrict | squeezes a VN opening degree is LPL. Not limited to areas. That is, the HPL + LPL region may be used as long as it is a region where a high supercharging pressure is required, that is, a high rotation region with a medium to high load.

  In the second embodiment described above, the case where the present invention is applied to the control of the diesel engine (compression ignition internal combustion engine) 10 has been described. However, the present invention is not limited to the diesel engine, but a gasoline engine (spark ignition internal combustion engine). Engine) and other various internal combustion engines.

  In the second embodiment described above, the first intake throttle valve 36 is the “first throttle valve” in the first invention, and the second intake throttle valve 38 is the “first throttle valve” in the first invention. It corresponds to “2 throttling valves”. Further, when the ECU 70 executes the process of step 202, the “determination means” in the first invention executes the process of step 206, so that the “control means” in the first invention changes. , Each has been realized.

  In the second embodiment described above, the turbocharger 24 corresponds to the “variable nozzle supercharger” according to the fifth aspect of the present invention. Further, the “supercharging pressure control means” in the fifth aspect of the present invention is realized by the ECU 70 executing the processing of step 208 described above.

Embodiment 3 FIG.
[Features of Embodiment 3]
Next, a third embodiment of the present invention will be described with reference to FIG. The present embodiment can be realized by causing the ECU 70 to execute a routine shown in FIG. 6 to be described later using the hardware configuration shown in FIG. In the description of the present embodiment, the difference from the above-described first embodiment will be mainly described, and the description of the same matters will be simplified or omitted.

  In the first embodiment described above, a large amount of LPL-EGR is introduced while securing the supercharging pressure by controlling the first intake throttle valve 36 in the LPL region, which is a high rotation region of medium and high loads. Can do.

  Here, in the EGR control, it is conceivable to introduce not only the external EGR but also the internal EGR. The internal EGR is performed by exhaust gas (burned gas) subjected to combustion in the cylinder remaining in the cylinder or sucked back again. That is, during the valve overlap period, that is, the period during which both the intake valve 62 and the exhaust valve 66 are opened by opening the intake valve 62 before the exhaust valve 66 is closed, the exhaust gas (burned gas) is in-cylinder and May be sucked back into the intake port. The exhaust gas thus sucked back then flows into the cylinder together with fresh air by the movement of the piston, thereby executing the internal EGR.

  The amount of internal EGR increases as the valve overlap period increases. Therefore, by driving the intake variable valve mechanism 64, the opening timing of the intake valve 62 is advanced, and by driving the exhaust variable valve mechanism 68, the closing timing of the exhaust valve 66 is delayed, thereby providing valve overlap. The internal EGR amount can be increased by extending the period.

  By utilizing such variable valve timing operation, the third embodiment increases the internal EGR when the intake air amount is controlled by the first throttle valve 36 in the first embodiment described above. And As a result, not only LPL-EGR but also internal EGR can be increased in the LPL region, that is, in the high rotation region with medium and high loads, so that an increase in NOx emission can be effectively suppressed.

[Specific Processing in Embodiment 3]
Next, with reference to FIG. 6, the specific content of the process performed in this Embodiment is demonstrated. FIG. 6 is a flowchart of a routine in which the ECU 70 executes intake air amount control.

  In the routine shown in FIG. 6, first, the operating conditions in the diesel engine 10 are read (step 300). Next, it is determined whether or not the operation region of the diesel engine 10 is the LPL region (step 302). Here, specifically, the same processing as steps 100 and 102 shown in FIG. 4 is executed.

  If it is determined in step 302 that the current operation region is not the LPL region, that is, if it is determined that the operation region is the HPL region or the HPL + LPL region, the process proceeds to the next step, and the second intake air Intake air amount control using the throttle valve 38 is executed (step 304).

  On the other hand, when it is determined in step 202 that the current operation region is the LPL region, the process proceeds to the next step, and intake air amount control using the first intake throttle valve 36 is executed (step). 306). At the same time, the internal EGR increase control is executed (step 308). Specifically, the valve overlap period is extended by driving the intake variable valve mechanism 64 and the exhaust variable valve mechanism 68.

  As described above, according to the system of the third embodiment, the internal EGR can be increased by expanding the valve overlap period in the LPL region, which is a high rotation region with medium and high loads. Thereby, since the amount of EGR can be increased effectively, an increase in the NOx emission amount can be effectively suppressed.

  By the way, in Embodiment 3 mentioned above, when the driving | running area | region of the diesel engine 10 turns into an LPL area | region, it is supposed that internal EGR will be increased, but the area | region which increases internal EGR is not restricted to an LPL area | region. That is, the HPL + LPL region may be used as long as EGR is to be increased.

  In the third embodiment described above, the case where the present invention is applied to the control of the diesel engine (compression ignition internal combustion engine) 10 has been described. However, the present invention is not limited to the diesel engine, but a gasoline engine (spark ignition internal combustion engine). Engine) and other various internal combustion engines.

  In the third embodiment described above, the first intake throttle valve 36 is the “first throttle valve” in the first invention, and the second intake throttle valve 38 is the “first throttle valve” in the first invention. It corresponds to “2 throttling valves”. Further, when the ECU 70 executes the process of step 302, the “determination means” in the first invention executes the process of step 306, so that the “control means” in the first invention changes. , Each has been realized.

  In the third embodiment described above, the intake variable valve mechanism 64 and the exhaust variable valve mechanism 68 correspond to the “internal EGR amount variable means” in the fourth aspect of the present invention. Further, the “internal EGR amount control means” according to the fourth aspect of the present invention is implemented by the ECU 70 executing the processing of step 308.

It is a figure for demonstrating schematic structure of the system 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 which shows a LPL area | region, a HPL area | region, and a HPL + LPL area | region. 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 2 of this invention. It is a flowchart of the routine performed in Embodiment 3 of the present invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Diesel engine 12 Injector 14 Common rail 16 Supply pump 18 Exhaust passage 20 Exhaust manifold 24 Turbocharger 26 Aftertreatment device 28 Intake passage 30 Air cleaner 32 Intercooler 34 Intake manifold 36 First intake throttle valve 38 Second intake throttle valve 40 HPL -EGR passage 42 HPL-EGR cooler 44 HPL-EGR valve 46 LPL-EGR passage 48 LPL-EGR cooler 50 LPL-EGR valve 52 Exhaust throttle valve 60 Crankshaft 62 Intake valve 64 Intake variable valve mechanism 66 Exhaust valve 68 Exhaust possible Variable valve mechanism 70 ECU (Electronic Control Unit)
72 Air Flow Meter 74 Intake Pressure Sensor 76 Back Pressure Sensor 78 Accelerator Opening Sensor 80 Crank Angle Sensor

Claims (5)

A supercharger provided in the intake passage of the internal combustion engine;
A first throttle valve disposed upstream of the supercharger in the intake passage;
A second throttle valve disposed downstream of the supercharger in the intake passage;
Control means for controlling the amount of intake air by adjusting the opening of the first throttle valve and / or the second throttle valve;
A determination means for determining whether or not the engine speed is in a high rotation range where the engine speed is equal to or higher than a predetermined value in a medium to high load range of the internal combustion engine
The control means includes
A control device for an internal combustion engine, wherein when it is determined that the engine is in the high rotation range, the intake air amount is controlled mainly by using the first throttle valve. The control means includes
2. The control device for an internal combustion engine according to claim 1, wherein when it is determined that the engine is in the high rotation region, the second throttle valve is fully opened. An EGR passage that connects a downstream side of the first throttle valve and an upstream side of the supercharger and an exhaust passage of the internal combustion engine in the intake passage;
An external EGR amount varying means for varying the amount of external EGR flowing back through the EGR passage;
An external EGR amount control means for controlling the external EGR amount variable means so as to increase the external EGR amount when it is determined to be in the high rotation region;
The control apparatus for an internal combustion engine according to claim 1, further comprising: An internal EGR amount variable means for changing the internal EGR amount by changing the valve overlap of the intake valve and the exhaust valve;
An internal EGR amount control means for controlling the internal EGR amount variable means so as to increase the internal EGR amount when it is determined to be in the high rotation region;
The control device for an internal combustion engine according to any one of claims 1 to 3, further comprising: The supercharger is a variable nozzle supercharger capable of adjusting the supercharging pressure,
The supercharging pressure control means for restricting the variable nozzle so as to increase the supercharging pressure when it is determined to be in the high rotation region, further comprising a supercharging pressure control means. Control device for internal combustion engine.

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