JP2010249022A - EGR system of internal combustion engine and control method thereof - Google Patents

Abstract

An EGR system for a two-stage supercharged internal combustion engine 2 having a high-pressure stage supercharger 4 and a low-pressure stage supercharger 3 includes a low-speed low-load operation state and a high-speed high-load operation state at start-up. A highly efficient EGR system and its control method are provided in all operating states of the internal combustion engine 2.
An EGR system for a two-stage supercharged internal combustion engine 2 having a high-pressure stage supercharger 4 and a low-pressure stage supercharger 3, wherein the EGR system 1 includes the high-pressure turbine 4T and the low-pressure stage turbocharger. A first EGR passage 5 for introducing EGR gas E through a first EGR valve 6 from an exhaust passage between the stage turbine 3T and an intake passage between the low-pressure stage compressor 3C and the high-pressure stage compressor 4C; A second EGR passage 7 for introducing EGR gas E from the exhaust manifold 12 of the internal combustion engine 2 to the intake manifold 11 via the second EGR valve 8, and the rotary shaft of the low pressure stage turbine 3 T in the low pressure stage supercharger 3. A load control device 13 for applying a load to
[Selection] Figure 1

Description

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

  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 turbocharger) and a small-capacity high-pressure stage turbo turbocharger (high-pressure turbocharger). (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, It is supplied to the engine 2 through an intake system constituted by a high-pressure compressor 4C, an intercooler 15a, and an intake manifold 11. The exhaust gas G discharged from the engine 2 is discharged from the exhaust manifold 12 to the outside through an exhaust system constituted by the high-pressure stage turbine 4T and the 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. The exhaust gas G is discharged from the engine 2 through the exhaust manifold 12 and the low pressure turbine 3T when the exhaust switching valve 17 is opened. 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).

  As another EGR system, an exhaust passage between the high-pressure turbine 4T and the low-pressure turbine 3T is provided via an EGR cooler 15b for cooling the EGR gas, and a first EGR valve 6 for controlling the flow rate of the EGR gas. In some cases, the first EGR passage 5 is connected to the intake passage between the low-pressure compressor 3C and the high-pressure compressor 4C. 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 is taken in from the exhaust pipe downstream of the high pressure turbine 4T and supplied to the first EGR passage 5, so that the entire amount of the exhaust gas G is exhausted to the exhaust manifold 12. To the high pressure turbine 4T. Since the exhaust gas G sufficiently performs the work of the high-pressure turbocharger 4, the turbocharger can be used in a highly efficient region regardless of the use of LP-EGR.

  However, the exhaust gas G flowing through the first EGR passage 5 flows due to the pressure difference between the inlet and outlet portions of the first EGR passage 5, that is, the pressure difference between the downstream region of the high-pressure turbine 4T and the downstream region of the high-pressure compressor 4C. 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 downstream from the low-pressure turbine 3T, or an intake throttle is placed in the intake passage between the air cleaner 14 and the high-pressure compressor 4C. It is necessary to install a valve. When this exhaust throttle valve or intake throttle valve 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, in a state where the turbocharger is not sufficiently charged, a pressure difference cannot be obtained between the inlet portion and the outlet portion of the first EGR passage 5, There is a problem that it becomes impossible to flow an EGR gas.

Japanese Patent Laid-Open No. 2007-100608

  The present invention has been made in view of the above situation, and an object thereof is to provide a two-stage supercharged internal combustion engine EGR system including a high-pressure supercharger and a low-pressure supercharger. To provide a highly efficient EGR system and its control method in all operating states of an internal combustion engine, including a low-speed and low-load operating state and a high-speed and high-load operating state.

  In order to achieve the above object, an EGR system according to the present invention is provided with a low-pressure stage compressor of a low-pressure stage turbocharger and a high-pressure stage compressor of a high-pressure stage supercharger in order from the upstream side of an intake passage and upstream of an exhaust passage. An EGR system of an internal combustion engine provided with a high-pressure stage turbine of a high-pressure stage supercharger and a low-pressure stage turbine of a low-pressure stage supercharger in order from the side, wherein the EGR system includes the high-pressure stage turbine and the low-pressure stage turbine. A first EGR passage for introducing EGR gas via a first EGR valve, an exhaust manifold of the internal combustion engine to an intake manifold, from an exhaust passage therebetween to an intake passage between the low pressure stage compressor and the high pressure stage compressor A second EGR passage for introducing EGR gas via a second EGR valve, and a load applied to the rotary shaft of the low-pressure stage turbine to the low-pressure stage supercharger And having a load control device.

  With this configuration, a load is applied to the rotating shaft of the low-pressure stage turbine, the pressure on the upstream side of the low-pressure stage turbine can be increased, and the pressure on the inlet side of the first EGR passage connected thereto can be increased. Thus, it can pass through the first EGR passage and circulate to the intake side. In addition, the entire amount of exhaust gas discharged from the internal combustion engine is supplied to the high-pressure turbine, and the high-pressure turbocharger performs work efficiently, and the intake air amount to the internal combustion engine increases. It can be carried out.

  In addition, the configuration that controls the flow rate of the EGR gas flowing through the first EGR passage with the load control device eliminates the need to install an exhaust throttle valve on the exhaust passage and an intake throttle valve on the intake passage, thereby suppressing the occurrence of pumping loss. can do.

  In the above EGR system, the load control device is a power generation device. With this configuration, electricity can be extracted from the load control device as energy, so that energy efficiency can be improved.

In order to achieve the above object, the EGR system control method according to the present invention is provided with a low-pressure stage compressor of a low-pressure stage turbocharger and a high-pressure stage compressor of a high-pressure stage supercharger in order from the upstream side of the intake passage. A high-pressure stage turbine of a high-pressure stage supercharger and a low-pressure stage turbine of a low-pressure stage supercharger are provided in order from the upstream side of the passage, and from the exhaust passage between the high-pressure stage turbine and the low-pressure stage turbine, A first EGR passage for introducing EGR gas to the intake passage between the high-pressure compressor and the first high-pressure compressor via the first EGR valve, and an EGR gas to the intake manifold from the exhaust manifold of the internal combustion engine to the intake manifold via the second EGR valve EGR system control method comprising: a second EGR passage to be introduced; and a load control device that applies a load to the rotary shaft of the low-pressure turbine in the low-pressure turbocharger When the internal combustion engine is in the first operating state, the internal combustion engine is supercharged by the high pressure stage supercharger, and a load is applied to the rotary shaft of the low pressure stage turbine by the load control device. And the first EGR valve is opened, and E is
The first control for performing GR is performed.

  With this configuration, for example, at the start of the internal combustion engine or in the first operating state such as the low-speed and low-load operating state, the entire amount of exhaust gas is caused to flow to the high-pressure turbine to quickly start up the high-pressure turbocharger, and The pressure on the inlet side of the first EGR passage can be increased by applying a load with the load control device. In other words, the high pressure supercharger can perform work regardless of the use of EGR, and can supply sufficient exhaust gas to the intake side via the first EGR passage.

  In the EGR system control method, the load control device is used as a power generator, and the internal combustion engine is supercharged by the high-pressure stage supercharger when the internal combustion engine is in a first operating state. The first control that applies a load to the rotating shaft of the low-pressure turbine by the power generator, stores the energy generated by the power generator in the power storage device, and performs EGR in the first EGR passage by opening the first EGR valve It is characterized by performing. With this configuration, electricity generated in the power generation device can be recovered as energy, so that energy efficiency can be improved.

  In the above EGR system control method, when the internal combustion engine is in the second operating state, the internal combustion engine is supercharged by the high-pressure stage supercharger and EGR is performed by the second EGR passage. The second control is performed. With this configuration, for example, in the second operation state such as a state where the high-pressure stage supercharger is sufficiently rotated, EGR using the second EGR passage is used rather than supplying exhaust gas to the high-pressure stage supercharger. Therefore, the EGR effect can be sufficiently obtained. Furthermore, the configuration for releasing the operation of the load control device and accelerating the rotation of the low-pressure stage turbine enables simultaneous preparation for smoothly switching from the high-pressure stage supercharger to the low-pressure stage supercharger. .

  In the above EGR system control method, when the internal combustion engine is in the third operating state, the internal combustion engine is supercharged by the low-pressure stage supercharger and EGR is performed by the second EGR passage. The third control is performed. With this configuration, for example, in the third operation state such as the high-speed and high-load operation state of the internal combustion engine, the low-pressure stage supercharger performs sufficient work and uses the second EGR passage while realizing large-capacity supercharging. Since the exhaust gas can efficiently recirculate the exhaust gas to the internal combustion engine, highly efficient EGR can be realized.

  According to the EGR system for an internal combustion engine and the control method therefor according to the present invention, an EGR system having a first EGR passage and a second EGR passage is introduced into a two-stage turbo system having a low-pressure stage supercharger and a high-pressure stage supercharger. In addition, by installing a load control device that applies a load to the rotary shaft of the low-pressure stage turbine, it is highly efficient in all operating states of the internal combustion engine, including low speed and low load operating conditions, high speed and high load operating conditions, etc. It is possible to provide an EGR system capable of EGR and a control method thereof.

It is the figure which showed the structure of the EGR system of embodiment which concerns on this invention. It is the figure which showed the structure of the EGR system of embodiment which concerns on this invention. It is the figure which showed the structure of the EGR system of embodiment which concerns on this invention. It is the figure which showed the control flow of the EGR system of embodiment which concerns on this invention. It is the figure which showed the structure of the conventional 2 stage turbo EGR system.

Hereinafter, an EGR system and a control method thereof according to embodiments of the present invention will be described with reference to the drawings. FIG. 1 shows a configuration of an EGR system 1 according to an embodiment of the present invention, in which a first EGR passage 5 and a second EGR passage 7 are installed in a two-stage turbo system, and a load is applied to the rotating shaft of the low-pressure turbine 3T. A control device 13 is installed.

  The first EGR passage 5 has an inlet portion provided in the exhaust passage downstream of the high-pressure stage turbine 4T and upstream of the low-pressure stage turbine 3T, an outlet portion provided upstream of the low-pressure stage compressor 3C, and the high-pressure stage compressor. It is provided in the intake passage downstream of 4C.

  In FIG. 1, the flow of intake air A, exhaust gas G, and EGR gas E is indicated by arrows, and the flow of each gas is determined when the engine (internal combustion engine) 2 is started or in a low-speed and low-load operation state. This shows a state of the first control in which the supercharging is performed by the high-pressure stage turbocharger (high-pressure stage supercharger) 4 and the EGR is performed by the first EGR passage 5.

  First, the flow of each gas 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 via the low pressure compressor 3C, the high pressure compressor 4C, the intercooler 15a, and the intake manifold 11.

  Exhaust gas G indicated by a black arrow is discharged from the engine 2 to the outside through the exhaust manifold 12, the high pressure turbine 4T, and the low pressure turbine 3T through a muffler (not shown). The EGR gas E indicated by the linear arrow passes through the first EGR passage 5, the EGR cooler 15b, and the first EGR valve 6 that are branched from the exhaust passage downstream of the high pressure turbine 4T and upstream of the low pressure turbine 3T. The air is supplied to the intake passage downstream of the low-pressure compressor 3C and upstream of the high-pressure compressor 4C. The EGR gas E is sent to the high-pressure compressor 4C together with the intake air A.

  Here, in order to efficiently flow the EGR gas E from the inlet portion to the outlet portion of the first EGR passage 5, a load is applied to the rotation of the low-pressure turbine 3T by the load control device 13. This is done by applying a load to the rotor blades of the low-pressure turbine 3T, thereby increasing the resistance when the exhaust gas G passes through the low-pressure turbine 3T. For this reason, the pressure upstream of the low-pressure turbine 3T, that is, the pressure at the inlet of the first EGR passage 5 increases. Since the pressure difference between the first EGR passage 5 and the outlet portion of the first EGR passage 5 increases due to the pressure increase at the inlet portion of the first EGR passage 5, the EGR gas E can flow efficiently.

  Further, since the entire amount of the exhaust gas G passes through the high-pressure stage turbine 4T, the high-pressure stage turbocharger 4 works sufficiently and the supercharging efficiency can be improved. Furthermore, energy efficiency can be improved by setting it as the structure which collect | recovers the rotational energy of the low pressure stage turbine 3T by using the load control apparatus 13 as a power generator.

  The control of the load control device 13 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 (ECU or the like) 19 shown in FIG.

  FIG. 2 shows the state of the second control. This second control is a control of the process in which the engine 2 shifts from the low speed and low load operation state to the second operation state such as the high speed and high load operation state. Supercharging is performed by the high pressure turbocharger 4 and EGR. Is a control for performing the above in the second EGR passage 7. This second control is a control in a state where the high-pressure stage turbocharger 4 is sufficiently working, that is, a state where the high-pressure stage compressor 3C is sufficiently rotated to perform supercharging (second operating state).

At this time, the intake air A and the exhaust gas G flow in the same passage as in the first control. The EGR gas E is supplied from the exhaust manifold 12 to the intake manifold 11 via the EGR cooler 15 c and the second EGR valve 8. That is, in this second control, EGR is performed via the second EGR passage 7 in which the inlet portion is provided in the exhaust manifold 12 and the outlet portion is provided in the intake manifold 11.

  Here, in the second control, the operation of the load control device 13 is stopped, and the low-pressure turbine 3T is controlled to accelerate the rotation by the passage of the exhaust gas G. In the state in which the second control is performed, the high-pressure turbocharger 4 works sufficiently, so that the intake negative pressure rises and the EGR gas E can be efficiently introduced into the intake manifold 11, thereby improving the EGR efficiency. .

  When the load control device 13 is a power generation device such as a motor, in this second control, a rotational force is applied to the low-pressure turbine 3T by this motor, and the low-pressure turbocharger (low-pressure turbocharger) 3 starts up. You may add control which shortens time.

  FIG. 3 shows the state of the third control. In the third control, the engine 2 is in a third operation state such as a high-speed and high-load operation state, and supercharging is performed by the low-pressure stage turbocharger (low-pressure stage supercharger) 3 and EGR is performed by the second EGR passage 7. It is the control performed in.

  At this time, intake air A is introduced from the air cleaner 14 and supplied to the engine 2 via the low-pressure compressor 3C, the intercooler 15a, and the intake manifold 11. That is, the intake air A is supplied to the engine 2 by bypassing the high-pressure compressor 4 </ b> C under the control of the intake air switching valve 16. The exhaust gas G is discharged from the exhaust manifold 12 to the outside through the low pressure turbine 3T. That is, the exhaust gas G is discharged to the outside by bypassing the high-pressure turbine 4T by the control for opening the exhaust gas switching valve 17. The EGR gas E is supplied to the intake manifold 11 via the second EGR passage 7. Here, the intake switching valve 16 and the exhaust switching valve 17 are controlled by a control device (not shown).

  In the third control, the operation of the load control device 13 is stopped, and the low-pressure stage turbocharger performs sufficient work, so that EGR using the second EGR passage 7 while realizing large-capacity supercharging, Since the exhaust gas G can be efficiently recirculated to the engine 2, a highly efficient EGR can be realized.

  FIG. 4 shows a control flow of the EGR system 1. When the EGR system 1 determines that the high-pressure turbocharger 4 is used in S2, and determines that the engine 2 is in the starting state or the low-speed and low-load operation state in S3 (first operation state), 1st control is performed (S10-S13 and S41-S42). That is, the first control using the first EGR passage 5 is started in S10, first, the load control device 13 is operated (S11), the pressure at the inlet of the first EGR passage 5 is increased (S12), and the first EGR valve 6 is opened (S13), and EGR gas E is supplied to the intake side (S4). When the load control device 13 is a power generation device, the load control device 13 generates power (S41) and performs control to store power in a power storage device such as a battery (S42).

  The control of the load control device 13 and the first EGR valve 6 and the like, the determination of the operating state of the engine 2 and the determination of the pressure increase in the exhaust passage, etc., are installed as appropriate with the control device (ECU etc.) 19 shown in FIG. This can be done by various sensors 18.

  Further, when the EGR system 1 determines in S2 that the high-pressure turbocharger 4 is used, and determines in S3 that the engine 2 is not in a starting state or a low-speed and low-load operating state (second operating state) ) Performs the second control (S20 to S23). That is, the second control using the second EGR passage 7 is started in S20, first the load control device 13 is stopped (S21), the second EGR valve 8 is opened (S23), and the EGR gas E is moved to the intake side. Supply (S4) control is performed.

  Further, when the load control device 13 is a power generation device such as a motor, the motor may be supplied from a power storage device such as a battery and a rotational force may be applied to the low-pressure turbine 3T. With this configuration, the rise time of the low-pressure stage turbocharger 3 is shortened, and the supercharging efficiency can be improved.

  Further, when the EGR system 1 determines that the high-pressure stage turbocharger 4 is not used in S2, that is, the supercharging is performed by the low-pressure stage turbocharger 3 (the third operation state), 3 control is performed (S30-S33). That is, the third control is started in S30. First, the stop of the load control device 13 is confirmed (S31), the second EGR valve 8 is opened (S33), and the EGR gas E is supplied to the intake side (S4). Take 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 (S10), and the engine 2 accelerates while performing EGR in the first EGR passage 5. As the engine 2 accelerates, the rotational speed of the high-pressure turbocharger 4 increases, and when it is determined that the rotational speed is sufficient (S3), the shift to the second control (S20) is started. That is, the load control device 13 is stopped, the first EGR valve 6 is closed, and the second EGR valve 8 is opened. Here, the determination of the rotational speed of the high-pressure stage turbocharger 4 (S3) can be made by measuring the intake negative pressure with, for example, the pressure sensor 18 installed in the intake passage upstream of the high-pressure stage compressor 4C.

  When the engine 2 is further accelerated and switched from the high-pressure turbocharger 4 to the supercharging by the low-pressure turbocharger 3, the shift to the third control (S30) is started. The switching from the high-pressure stage turbocharger 4 to the low-pressure stage turbocharger 3 can utilize the control of the conventional two-stage turbo system. That is, the EGR system 1 is configured to simultaneously perform EGR control and two-stage turbo control.

  As described above, the first control, the second control, and the third control are selected according to the operating state of the engine 2 and the EGR is performed, so that the EGR is efficiently performed in all the operating states of the engine 2. It becomes possible. In particular, it is possible to provide an EGR system that improves the efficiency of EGR when starting the engine 2 or during low speed and low load, and realizes NOx reduction.

  In other operation states, the second EGR passage 7 is basically used, and the operation region of the turbochargers 3 and 4 is controlled by an operation map created on the assumption that the second EGR passage 7 is used.

1 EGR system 2 Engine (internal combustion engine)
3 Low-pressure turbocharger (low-pressure turbocharger)
3C Low-pressure compressor 3T Low-pressure turbine 4 High-pressure turbocharger (high-pressure turbocharger)
4C High-pressure stage compressor 4T High-pressure stage turbine 5 First EGR passage 6 First EGR valve 7 Second EGR passage 8 Second EGR valve 11 Intake manifold 12 Exhaust manifold 13 Load control device

Claims (6)

A low-pressure stage compressor of the low-pressure stage supercharger and a high-pressure stage compressor of the high-pressure stage supercharger are provided in order from the upstream side of the intake passage, and the high-pressure turbine and low-pressure stage supercharger of the high-pressure stage turbocharger are arranged in order from the upstream side of the exhaust passage. An EGR system for an internal combustion engine provided with a low-pressure turbine of a feeder,
The EGR system introduces EGR gas from an exhaust passage between the high-pressure stage turbine and the low-pressure stage turbine to an intake passage between the low-pressure stage compressor and the high-pressure stage compressor via a first EGR valve. A first EGR passage to
A second EGR passage for introducing EGR gas from the exhaust manifold of the internal combustion engine to the intake manifold via a second EGR valve;
An EGR system comprising a load control device for applying a load to a rotary shaft of the low-pressure stage turbine in the low-pressure stage supercharger.   The EGR system according to claim 1, wherein the load control device is a power generation device. A low-pressure stage compressor of the low-pressure stage supercharger and a high-pressure stage compressor of the high-pressure stage supercharger are provided in order from the upstream side of the intake passage, and the high-pressure turbine and low-pressure stage supercharger of the high-pressure stage turbocharger are arranged in order from the upstream side of the exhaust passage. A low-pressure turbine for the feeder,
A first EGR passage for introducing EGR gas from an exhaust passage between the high-pressure turbine and the low-pressure turbine to an intake passage between the low-pressure compressor and the high-pressure compressor via a first EGR valve; ,
A second EGR passage for introducing EGR gas from the exhaust manifold of the internal combustion engine to the intake manifold via a second EGR valve;
A control method for an EGR system having a load control device for applying a load to a rotary shaft of the low-pressure stage turbine on the low-pressure stage supercharger,
When the internal combustion engine is in the first operating state, the internal combustion engine is supercharged by the high pressure stage supercharger, and a load is applied to the rotary shaft of the low pressure stage turbine by the load control device, A control method for an EGR system, wherein the first control for performing EGR in the first EGR passage is performed by opening the first EGR valve. A control method of the EGR system using the load control device as a power generation device,
When the internal combustion engine is in the first operating state, the internal combustion engine is supercharged by the high-pressure stage supercharger, a load is applied to the rotating shaft of the low-pressure stage turbine by the power generator, A control method for an EGR system that performs first control for storing energy generated in a power generation device in a power storage device and performing EGR in a first EGR passage by opening the first EGR valve.   When the internal combustion engine is in a second operating state, the internal combustion engine is supercharged by the high-pressure stage supercharger, and second control is performed to perform EGR in the second EGR passage. The control method of the EGR system according to claim 3 or 4.   When the internal combustion engine is in a third operating state, the internal combustion engine is supercharged by the low-pressure stage supercharger and third control is performed to perform EGR in the second EGR passage. The method for controlling an EGR system according to any one of claims 3 to 5.

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