JP2010255525A - Internal combustion engine and method for controlling the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an internal combustion engine and a method for controlling the same enabling efficient EGR in all operation states of the internal combustion engine 2 including a low speed light load operation state and a high speed heavy load operation state at the time of a start in the two stage supercharging type internal combustion engine equipped with a high pressure stage supercharger 4 and a low pressure stage supercharger 3. <P>SOLUTION: In the internal combustion engine including a multi-stage supercharging system and an EGR system, the EGR system 1 is composed of a first EGR passage 5 introducing EGR gas from an exhaust gas passage at a downstream of a low pressure stage turbine 3T to an intake air passage at an upstream of a low pressure stage compressor 3C, a second EGR passage 7 introducing EGR gas E from an exhaust manifold 12 of the internal combustion engine 2 to an intake manifold 11, and an intake air passage changeover valve 10 disposed in the intake air passage between a branch P1 and the low pressure stage compressor 3C, a high pressure stage supercharger 4 is composed of a supercharger, and a low pressure stage supercharger 3 is composed in such a manner that it is operated by an exhaust gas turbine, operated by an electric motor, or operates a generator. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a two-stage supercharging internal combustion engine having a high-pressure stage supercharger and a low-pressure stage supercharger, and more specifically, an internal combustion engine that performs EGR at a high rate in all operating states of the internal combustion engine and the engine It relates to a control method.

  In order to reduce NOx in the exhaust gas of the engine (internal combustion engine), EGR (Exhaust Gas Recirculation) that recirculates the exhaust gas to the intake side is performed. The EGR system is a system in which exhaust gas generated in an engine is mixed with intake air and sent again into a combustion chamber.

  On the other hand, in order to improve the exhaust gas performance and fuel consumption performance of NOx-PM (particulate matter) of the engine, a multistage supercharging system in which a plurality of superchargers are installed in the engine is adopted. This multi-stage turbocharging system includes, for example, a two-stage turbo system using two superchargers. A large-capacity low-pressure stage turbocharger (low-pressure stage supercharger) and a small-capacity high-pressure stage turbocharger (high-pressure stage). (Supercharger) are connected in series. In this two-stage turbo system, control is performed so that the high-pressure stage turbocharger performs supercharging with a high-pressure stage turbocharger when the engine is running at low speed and low load, and the high-pressure stage turbocharger is used to supercharge a large flow rate when the engine is running at high speed and high load. ing.

  In this two-stage turbo system, the optimum efficiency of the turbocharger in each operating state of the engine can be obtained by using a plurality of turbochargers with different capacities in parallel, in series or independently in various operating states of engine rotation and load. Can be used. For this reason, by adopting this system, fuel consumption can be improved and exhaust gas can be reduced.

  An engine in which the above-described EGR system is applied to this multistage supercharging system has been proposed (see, for example, Patent Document 1). FIG. 5 shows an outline of the conventional EGR system 1X. Hereinafter, control of the EGR system applied to a two-stage turbo system which is a multistage supercharging system will be described.

  First, the configuration and control of the two-stage turbo system will be described. In the low-speed and low-load operation state of the engine 2, supercharging is performed by the high-pressure stage turbocharger 4 having the high-pressure stage compressor 4C and the high-pressure stage turbine 4T. At this time, the intake air A is supplied from the air filter 14 to the low-pressure stage compressor 3C, A high pressure compressor 4C, an intercooler 15a, and an intake manifold 11 are supplied to the engine 2 through an intake passage. Exhaust gas G discharged from the engine 2 is discharged from the exhaust manifold 12 to the outside through an exhaust passage having a high-pressure stage turbine 4T and a low-pressure stage turbine 3T.

  In the high speed and high load operation state of the engine 2, supercharging is performed by the low pressure stage turbocharger 3 having the low pressure stage compressor 3 </ b> C and the low pressure stage turbine 3 </ b> T. At this time, the intake air A is The compressor 3C supplies the engine 2 through the intercooler 15a and the intake manifold 11. Further, the exhaust gas G is discharged from the engine 2 through the exhaust manifold 12 and the low-pressure turbine 3T by opening the exhaust switching valve 17. That is, control is performed so as to bypass the high-pressure turbocharger 4.

Next, the configuration and control of the EGR system will be described. The EGR system generally includes a second EGR passage 7 that connects the exhaust manifold 12 and the intake manifold 11 via an EGR cooler 15c for cooling the EGR gas and a second EGR valve 8 that controls the flow rate of the EGR gas. It consists of. This EGR system is referred to herein as high pressure EGR (hereinafter referred to as HP-EGR).

  Further, as a different EGR system, an EGR cooler 15b for cooling EGR gas and a first EGR valve 6 for controlling the flow rate of EGR gas, an exhaust passage downstream of the low-pressure turbine 3T, an air cleaner 14 and a low pressure In some cases, the first EGR path 5 is connected to the intake passage to the stage compressor 3C. This EGR system is referred to herein as a ropeless EGR (hereinafter referred to as LP-EGR).

  The EGR system 1X is controlled by a control device 19 called an ECU (Engine Control Unit) connected to the first EGR valve 6, the second EGR valve 8, and various sensors (pressure sensor, temperature sensor) 18 through signal lines.

  According to the EGR system 1X in which both HP-EGR and LP-EGR are applied to a two-stage turbo system, these two types of EGR are selectively controlled according to the operating state of the engine, so that NOx in exhaust gas and PM and the like can be reduced.

  However, the above-mentioned HP-EGR and LP-EGR have their own problems. First, for example, in an operating state in which the engine 2 is operated at a low speed and a low load, high-pressure turbocharger 4 is used as a supercharging device, high supercharging is performed, and fuel efficiency is improved, and EGR is performed to reduce exhaust gas. The problem when performing this is explained.

  In the low-load operation state of the engine 2 at low speed, HP-EGR takes in EGR gas from the exhaust manifold 12 upstream of the high-pressure stage turbine 4T and supplies it to the second EGR passage 7, so that the exhaust gas G supplied to the high-pressure stage turbine 4T is supplied. The flow rate decreases. For this reason, the work amount of the high-pressure stage turbocharger 4 is reduced and the supercharging amount is reduced, so that the amount of intake air A supplied to the engine 2 is reduced. For this reason, there is a problem that the amount of air supplied to the engine 2 is insufficient, smoke is generated, and NOx cannot be reduced. Further, since the high-pressure turbocharger 4 does not work sufficiently, there is a problem that the turbocharger must be used in a low efficiency region.

  Further, in the LP-EGR in the low speed and low load operation state of the engine 2, the EGR gas passes through the high pressure turbine 4T, is taken in from the exhaust pipe downstream of the low pressure turbine 3T, and is supplied to the first EGR passage 5. Can be supplied from the exhaust manifold 12 to the high-pressure turbine 4T. Since the exhaust gas sufficiently performs the work by the exhaust gas, the high pressure turbocharger 4 can be used in a highly efficient region regardless of the use of LP-EGR.

  However, the EGR gas flowing through the first EGR passage 5 flows due to the pressure difference between the inlet and outlet of the first EGR passage 5, that is, the pressure difference between the downstream area of the low-pressure turbine 3T and the air cleaner 14 and the low-pressure compressor 3C. It becomes composition. It is necessary to create a pressure difference for flowing this EGR gas, and an exhaust throttle valve 22 is installed in the exhaust passage further downstream from the EGR gas intake section downstream from the low-pressure stage turbine 3T, or a high-pressure stage compressor is connected from the air cleaner 14. It is necessary to install an intake throttle valve 23 in the intake passage between 4C. When the exhaust throttle valve 22 or the intake throttle valve 23 is used, there is a problem that an increase in pumping loss, which is a resistance when the engine 2 sucks air, is caused, and the engine output performance is adversely affected.

  Further, in the operating state of the engine 2 having a low intake negative pressure, that is, when the supercharging by the high-pressure turbocharger 4 is not sufficiently performed, a pressure difference is obtained between the inlet portion and the outlet portion of the first EGR passage 5. However, there is a problem that it is impossible to flow a sufficient EGR gas.

Japanese Patent Laid-Open No. 2007-100608

  The present invention has been made in view of the above-described situation, and an object of the present invention is to provide a two-stage supercharging internal combustion engine including a high-pressure stage supercharger and a low-pressure stage supercharger at the time of starting, at a low speed and a low load. It is an object of the present invention to provide an internal combustion engine that realizes high-efficiency EGR in all operation states of the internal combustion engine, including an operation state and a high-speed and high-load operation state, and a control method thereof.

  In order to achieve the above object, an internal combustion engine according to the present invention is an internal combustion engine having a multistage supercharging system in which a low pressure supercharger and a high pressure supercharger are installed. , A first intake passage that communicates the junction, the intercooler, and the intake manifold, and a low-pressure compressor that communicates from the branch portion and a second intake passage that communicates the junction. A first EGR passage configured to introduce EGR gas from the exhaust passage downstream of the low-pressure stage turbine to the intake passage upstream of the low-pressure stage compressor via the first EGR valve; and from the exhaust manifold of the internal combustion engine A second EGR passage for introducing EGR gas to the intake manifold via the second EGR valve, and an intake passage between the branch section and the low-pressure compressor are provided. And an intake passage switching valve that constitutes an EGR system, the high-pressure stage supercharger is constituted by a supercharger, and the low-pressure stage supercharger is operated by an exhaust turbine and motor operation or generator operation. It is characterized in that it can be performed.

  With this configuration, since the first EGR passage is installed from the downstream of the low pressure turbine to the upstream of the low pressure compressor, the intake passage switching valve is closed, the low pressure turbocharger is operated as an electric motor, and the low pressure compressor is operated. The EGR gas can be supercharged by the rotating control. Thereby, since the amount of EGR increases, it is possible to reduce exhaust gas and improve fuel consumption.

  Further, exhaust gas energy that has conventionally been discarded by opening the wastegate of the turbocharger can be recovered by operating the generator of the low-pressure supercharger.

  In order to achieve the above object, a control method for an internal combustion engine according to the present invention includes: a low pressure stage supercharger; and an internal combustion engine having a multistage supercharging system provided with a high pressure stage supercharger. A first intake passage that communicates a high-pressure compressor, a merging section, an intercooler, and an intake manifold; and a second intake passage that communicates a low-pressure compressor and the merging section from the branch section. A first supercharger system configured to introduce EGR gas from an exhaust passage downstream of the low-pressure stage turbine to an intake passage upstream of the low-pressure stage compressor via the first EGR valve; A second EGR passage for introducing EGR gas from the manifold to the intake manifold via a second EGR valve, and an intake between the branch section and the low-pressure compressor. And an intake passage switching valve installed in the passage to constitute an EGR system, the high pressure stage supercharger is constituted by a supercharger, and the low pressure stage supercharger is operated by an exhaust turbine and an electric motor. A control method for an internal combustion engine configured to be able to perform a generator operation, wherein when the internal combustion engine is in a first operation state, the intake passage switching valve is closed, and the first intake passage is passed through, Supercharging is performed by the high-pressure stage supercharger, and the low-pressure stage supercharger is operated as an electric motor, the opening degree of the first EGR valve is controlled, and the EGR passage is connected to the low-pressure stage compressor via the first EGR passage. The first control for introducing the gas is performed.

  With this configuration, for example, when the internal combustion engine is started or in a first operating state such as a low-speed low-load operating state to a medium-speed medium-load operating state, the EGR gas passing through the first EGR is converted into the motor operation of the low-pressure supercharger. Therefore, the EGR amount increases, and exhaust gas can be reduced and fuel consumption can be improved.

  In the above internal combustion engine control method, when the internal combustion engine is in the second operating state, the intake passage switching valve is opened, and the supercharging is performed by the low-pressure compressor through the second intake passage. And performing a second control of operating the low-pressure stage supercharging as a generator, controlling the opening degree of the second EGR valve, and introducing EGR gas into the intake manifold via the second EGR passage. To do.

  With this configuration, for example, when the low-pressure supercharger is in the overspeed state in the second operation state such as the high-speed and high-load operation state of the internal combustion engine, this rotational force is recovered by the power generation operation of the low-pressure stage supercharger. Energy efficiency can be improved.

  In the internal combustion engine control method, when the internal combustion engine is in the third operating state, the intake passage switching valve is opened, and the supercharging is performed by the low-pressure compressor through the second intake passage. And the 3rd control which controls the opening degree of the 2nd EGR valve, and introduces EGR gas into the intake manifold via the 2nd EGR passage is performed.

  With this configuration, for example, in the third operation state such as the medium speed / medium load operation state of the internal combustion engine to the high speed / high load operation state, the low pressure stage supercharger performs sufficient work to realize a large capacity supercharge. However, since the exhaust gas can be efficiently recirculated to the internal combustion engine by the EGR using the second EGR passage, highly efficient EGR can be realized.

  According to the internal combustion engine and the control method thereof according to the present invention, an EGR system having a first EGR passage and a second EGR passage is introduced into a two-stage supercharging system having a low pressure supercharger and a high pressure supercharger, and The high-pressure stage supercharger is a supercharger, and the low-pressure stage supercharger can be operated by an exhaust turbine and an electric motor or a generator. It is possible to provide an internal combustion engine in which high efficiency EGR is realized and exhaust gas is reduced, and a control method for the internal combustion engine, in all operating states of the internal combustion engine including a medium-speed operation state and a high-speed and high-load operation state.

It is a figure showing composition of an internal-combustion engine of an embodiment concerning the present invention. It is a figure showing composition of an internal-combustion engine of an embodiment concerning the present invention. It is the figure which showed the control flow of the internal combustion engine of embodiment which concerns on this invention. It is the figure which showed the control map of the supercharging system and EGR system of embodiment which concerns on this invention. It is the figure which showed the structure of the EGR system of the 2 stage turbo of a prior art.

Hereinafter, an internal combustion engine and a control method thereof according to embodiments of the present invention will be described with reference to the drawings. FIG. 1 shows the configuration of an EGR system 1 according to an embodiment of the present invention.
This EGR system 1 is provided with a first EGR passage 5 and a second EGR passage 7 in a two-stage supercharging system.

  Specifically, the air cleaner 14, the branch portion P 1, the high-pressure stage compressor (supercharger) 9, the junction portion P 2, the intercooler 15 a and the intake manifold 11 communicate with each other, and the branch portion P 1 extends from the low-pressure stage. It has the 2nd intake passage 26 which connects the compressor 3C and the confluence | merging part P2.

  Further, the EGR gas is introduced through the first EGR valve 6 from the inlet P3 provided in the exhaust passage downstream of the low-pressure turbine 3T to the outlet P4 provided in the intake passage upstream of the low-pressure compressor 3C. 1 EGR passage 5, second EGR passage 7 for introducing EGR gas from the exhaust manifold 12 of the engine (internal combustion engine) 2 to the intake manifold 11 via the second EGR valve 8, and between the branch portion P 1 and the low-pressure stage compressor 3 C The intake passage switching valve 10 is provided in the intake passage.

  Further, the high-pressure stage supercharger is constituted by the supercharger 9, and the low-pressure stage supercharger 3 is constituted so that the operation by the exhaust turbine and the motor operation or the generator operation can be performed.

  Here, the supercharger 9 is a supercharger configured to operate the high-pressure compressor not by the power of exhaust gas but by the power of the engine 2 or the like.

  In FIG. 1, the flow of intake air A, exhaust gas G, and EGR gas E is indicated by arrows. The flow of each gas is determined when the engine (internal combustion engine) 2 is started or at low speed, low load, or medium speed. It shows a first operation state such as an intermediate load operation state, in which supercharging is performed by the high-pressure stage supercharger (supercharger) 9 and EGR is performed by the first EGR passage 5.

  First, the flow of each gas in the first control will be described. The intake air A indicated by the white arrow is introduced from the air cleaner 14 and supplied to the engine 2 through the branching part P1, the high-pressure compressor (supercharger) 9, the merging part P2, the intercooler 15a, and the intake manifold 11. Here, the intake air switching valve 10 is in a closed state.

  Further, the exhaust gas G indicated by the black arrow is discharged from the engine 2 to the outside through the exhaust manifold 12, the low-pressure turbine 3T, and the aftertreatment device 20 through a muffler (not shown). Further, the EGR gas E indicated by the linear arrow passes downstream of the intake passage switching valve 10 via the EGR cooler 15b of the first EGR passage 5 and the first EGR valve 6 branched from the exhaust passage downstream of the low-pressure stage turbine 3T. And it supplies to the intake passage upstream of the low-pressure compressor 3C. The EGR gas E is merged with the intake air A at the merge portion P2 and sent to the intercooler 15a.

  Here, in order to efficiently flow the EGR gas E from the inlet portion P3 to the outlet portion P4 of the first EGR passage 5, the compressor 3C of the low-pressure supercharger 3 is operated as an electric motor. As a result, the pressure on the upstream side of the low-pressure stage compressor 3C, that is, the outlet portion P4 of the first EGR passage 5, decreases, and the pressure on the downstream side of the low-pressure stage turbine 3T, that is, the inlet portion P3 of the first EGR passage 5 increases. That is, by the configuration in which the EGR gas E is supercharged by the low pressure supercharger 3, the pressure difference between the inlet portion P3 and the outlet portion P4 of the first EGR passage 5 is increased, and the EGR gas E can be efficiently flowed. It becomes like this.

  Note that the control of the low-pressure stage supercharger 3 and the first EGR valve 6 and the like, the determination of the operating state of the engine 2, and the like can be performed by the control device 19 shown in FIG.

  In FIG. 2, the flow of the intake air A, the exhaust gas G, and the EGR gas E is indicated by arrows, and the flow of each gas is such that the engine (internal combustion engine) 2 is in a high-speed and high-load operation state, etc. This shows a second operation state in which the low-pressure turbine 3T is in an over-rotation state, in which supercharging is performed by the low-pressure supercharger 3 and EGR is performed by the second EGR passage 7. At this time, the intake passage switching valve 10 is opened, and the intake air A is supercharged by the low-pressure compressor 3C and supplied to the engine 2.

  In the second control, when the low-pressure stage turbine 3T is in an overspeed state, the rotational energy of the low-pressure stage turbine 3T is suppressed while the rotational speed of the low-pressure stage turbine 3T is suppressed by setting the low-pressure stage supercharger 3 to a generator operation. It is characterized by collecting. Conventionally, the wastegate provided in the low-pressure stage turbine 3T is opened, and the exhaust gas G is discharged to the outside to suppress over-rotation of the low-pressure stage turbine 3T. Therefore, it is difficult to recover the energy that the exhaust gas G has.

  Further, in the third operation state in which the engine 2 is in a medium to medium load to high speed and high load operation state, the supercharging is performed by the low pressure supercharger 3 and the third control using the second EGR passage 7 is performed. Do. In the third control, the flow of each gas is the same as that in the second control, but the low-pressure stage supercharger 3 is controlled by an exhaust turbine operation instead of a generator operation. In other words, the low-pressure turbine 3T is rotated by the exhaust gas G discharged from the engine 2, the rotational force is transmitted to the low-pressure compressor 3C, and the intake air A is supercharged by the rotation of the low-pressure compressor 3C. .

  By this third control, the low-pressure supercharger 3 performs work sufficiently and realizes a large-capacity supercharging, while the exhaust gas G is efficiently recirculated to the engine 2 by EGR using the second EGR passage 7. Since it can circulate, highly efficient EGR is realizable.

  FIG. 3 shows a control flow of the EGR system 1. In S2, the EGR system 1 determines the engine operating state and the supercharging state, and selects execution of EGR by the first EGR passage 5 or the second EGR passage 7. When EGR by the first EGR passage 5 is selected (S3), the intake passage switching valve 10 is closed (S4), and it is determined that the operation state is the first (S10). In the first operating state, the low pressure stage supercharger 3 is operated as an electric motor (S11), and the first control is executed. In the first control, the high pressure supercharger (supercharger) 9 may be operated (S12).

  The control of the low pressure stage supercharger 3 and the first EGR valve 6 and the determination of the operating state and the supercharging state of the engine 2 are made by the control device (ECU etc.) 19 shown in FIG. It can be carried out.

  Further, when the EGR system 1 selects the EGR by the second EGR passage 7 in S2 (S5), the EGR system 1 opens the intake passage switching valve 10 (S6). After that, when it is determined that the rotation speed of the low-pressure stage supercharger 3 exceeds the predetermined rotation speed (first threshold) (S7), the second operation state (S20). to decide. In the second operating state, the second control is executed in which the low-pressure stage supercharger 3 is operated as a generator (S21). Here, the generated electricity is stored in a power storage device or the like installed together with the engine 2 (S22).

  Further, when it is determined that the rotation speed of the low-pressure stage supercharger 3 does not exceed the first threshold value (S7), it is determined that it is the third operation state (S30). In the third operating state, the third control is executed in which the low-pressure stage supercharger 3 is operated as an exhaust turbine (S31).

FIG. 4A shows a control map of the supercharging system showing the relationship between the operating state of the engine 2 and the supercharging state. The vertical axis indicates the fuel injection amount, the horizontal axis indicates the engine speed, and F1 to F3 indicate each supercharging. The state of control of the vessel is shown.

  Specifically, when the engine 2 is started or in a low-speed and low-load operation state, control (F1-1) is performed to operate the low-pressure supercharger 3 as an electric motor. In addition to the motor operation of the stage supercharger 3, control (F1) for operating the high-pressure stage supercharger (supercharger) 9 is performed. Further, when the engine 2 is in a medium to medium load to high speed and high load operation state, and the low pressure turbine 3T is in an overspeed state, control for operating the low pressure stage supercharger 3 as a generator (F2). In other medium / medium-speed to high-speed / high-load operation states, control (F3) for operating the low-pressure supercharger 3 in the exhaust turbine is performed.

  Similarly, FIG. 4B shows a control map of the EGR system showing the relationship between the operating state of the engine 2 and the passage for EGR. Specifically, when the engine 2 is started or in a low-speed and low-load to medium-speed and medium-load operation state, control (f1) for performing EGR in the first EGR passage 5 is performed. Then, control (f2) for performing EGR in the second EGR passage 7 is performed.

  That is, FIG. 4 summarizes the states of the supercharging system and the EGR system in the engine 2. For example, when the engine 2 is started or when the engine 2 is in a starting state or a low to low load to a medium to middle load operation state (first operation state). The EGR system performs EGR through the first EGR passage 5 (f1), and the supercharging system operates the electric motor (F1-1) of the low pressure stage supercharger 3, or the high pressure stage supercharger (supercharger) 9 described above. Control (F1) with operation is performed. This control is the first control.

  When the engine 2 is in a high speed and high load operation state and the low pressure supercharger 3 is in an overspeed state (second operation state), the EGR system performs EGR through the second EGR passage 7 (f2), The system performs the generator operation (F2) of the low-pressure stage supercharger 3. This control is the second control.

  Further, when the engine 2 is in the medium speed / medium load operation state to the high speed / high load operation state (third operation state), the EGR system performs EGR through the second EGR passage 7 (f2), and the supercharging system is the low pressure stage supercharger. 3 performs the exhaust turbine operation (F3). This control is the third control.

  Next, as a specific example of control, for example, control when the engine 2 accelerates from a stopped state and reaches a high speed and high load operation state will be described. First, when the engine is started, the first control is selected (S3, 4, 10-12), and the engine 2 accelerates while performing EGR in the first EGR passage 5. At this time, supercharging of the intake air A is performed by a high-pressure supercharger (supercharger) 9. In addition, since the EGR gas E is supercharged by operating the electric motor of the low-pressure stage supercharger 3, an EGR amount is increased, a highly efficient EGR is realized, and an exhaust gas is reduced and a control method thereof is provided. It becomes possible to do.

  Next, with the acceleration of the engine 2, the EGR is switched to the second EGR passage 7 (S5), and a third control (S30) is performed in which the low-pressure supercharger 3 is operated as an exhaust turbine. At this time, the high-pressure supercharger (supercharger) 9 has stopped operating.

  Next, when the number of revolutions of the engine 2 further increases and the number of revolutions of the low-pressure supercharger 3 exceeds the first threshold value and it is determined that the engine is overspeeding (S7), the second control (S20) is performed. At this time, the low-pressure stage supercharger 3 performs the generator operation (S21) and stores the energy in the power storage device (S22), thereby recovering the energy of the exhaust gas, so that the energy efficiency can be improved.

  As described above, according to the configuration in which the first control, the second control, and the third control are selected according to the operation state of the engine 2 and the control of the multistage supercharging system and the EGR system is performed, Thus, EGR can be performed efficiently. In particular, EGR at the time of starting the engine 2 or in a low-speed and low-load operation state, which has been difficult in the past, can be improved by supercharging the EGR gas E by the low-pressure stage supercharger 3, and NOx reduction has been realized. It becomes possible to provide an EGR system.

1 EGR system 2 Engine (internal combustion engine)
3 Low pressure turbocharger (low pressure turbocharger)
3C Low-pressure stage compressor 3T Low-pressure stage turbine 4 High-pressure stage supercharger (High-pressure stage turbocharger)
4C High-pressure compressor 5 First EGR passage 6 First EGR valve 7 Second EGR passage 8 Second EGR valve 9 Supercharger 10 Intake passage switching valve 11 Intake manifold 12 Exhaust manifold 25 First intake passage 26 Second intake passage

Claims (4)

In an internal combustion engine having a multistage supercharging system in which a low pressure stage supercharger and a high pressure stage supercharger are installed,
A first intake passage that communicates from the air cleaner to the branch section, the high-pressure stage compressor, the merging section, the intercooler, and the intake manifold, and a second intake passage that communicates from the branch section to the low-pressure stage compressor and the merging section. A two-stage supercharging system,
A first EGR passage for introducing EGR gas via a first EGR valve from an exhaust passage downstream of the low-pressure stage turbine to an intake passage upstream of the low-pressure stage compressor, and from the exhaust manifold of the internal combustion engine to the intake manifold, An EGR system having a second EGR passage for introducing EGR gas via a 2EGR valve and an intake passage switching valve installed in an intake passage between the branch portion and the low-pressure compressor;
An internal combustion engine characterized in that the high-pressure stage supercharger is constituted by a supercharger, and the low-pressure stage supercharger is configured to be able to perform an operation by an exhaust turbine and a motor operation or a generator operation. In an internal combustion engine having a multistage supercharging system in which a low pressure stage supercharger and a high pressure stage supercharger are installed,
A first intake passage that communicates from the air cleaner to the branch section, the high-pressure stage compressor, the merging section, the intercooler, and the intake manifold, and a second intake passage that communicates from the branch section to the low-pressure stage compressor and the merging section. A two-stage supercharging system,
A first EGR passage for introducing EGR gas via a first EGR valve from an exhaust passage downstream of the low-pressure stage turbine to an intake passage upstream of the low-pressure stage compressor, and from the exhaust manifold of the internal combustion engine to the intake manifold, An EGR system having a second EGR passage for introducing EGR gas via a 2EGR valve and an intake passage switching valve installed in an intake passage between the branch portion and the low-pressure compressor;
The high-pressure stage supercharger is constituted by a supercharger, and the low-pressure stage supercharger is a control method for an internal combustion engine configured to perform an operation by an exhaust turbine and a motor operation or a generator operation,
When the internal combustion engine is in the first operating state, the intake passage switching valve is closed, and the high pressure supercharger is supercharged through the first intake passage,
In addition, the low-pressure supercharger is operated as an electric motor, the opening degree of the first EGR valve is controlled, and the first control for introducing EGR gas into the low-pressure compressor through the first EGR passage is performed. A control method for an internal combustion engine. When the internal combustion engine is in the second operating state, the intake passage switching valve is opened, and supercharging is performed by the low pressure compressor through the second intake passage,
And performing a second control of operating the low-pressure stage supercharging as a generator, controlling the opening degree of the second EGR valve, and introducing EGR gas into the intake manifold via the second EGR passage. The method for controlling an internal combustion engine according to claim 2. When the internal combustion engine is in the third operating state, the intake passage switching valve is opened, and supercharging is performed by the low-pressure compressor through the second intake passage.
4. The internal combustion engine according to claim 2, wherein an opening degree of the second EGR valve is controlled, and third control for introducing EGR gas into the intake manifold is performed via the second EGR passage. 5. Control method.

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