JP2012102634A - Internal combustion engine, and method for controlling internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a technology that improves fuel economy while obtaining a desired amount of EGR gas.SOLUTION: In re-circulating a low-pressure EGR gas by a low-pressure EGR device 15 to achieve a target supercharging pressure, a compressor 5a is driven in an auxiliary manner by an electric motor 13 and a variable nozzle 14 is opened as the subsidiary driving force of the electric motor 13 becomes larger. A target supercharging pressure can be attained by the electric motor 13 while obtaining a desired amount of EGR gas. In addition, the opened variable nozzle 14 prevents an increase in an exhaust pressure on the upstream side of a turbine 5b, thereby reducing pump loss, thus improving fuel economy.

Description

  The present invention relates to an internal combustion engine and a method for controlling the internal combustion engine.

  A turbocharger having a variable nozzle in a turbine and an electric motor attached to a rotating shaft is known. By having the variable nozzle, it is possible to adjust the turbine rotation speed by changing the flow velocity of the exhaust gas flowing into the turbine by opening and closing the variable nozzle, and it is possible to adjust the supercharging pressure regardless of the exhaust gas flow rate. By having the electric motor, the boost pressure of a required magnitude can be obtained when necessary, regardless of the amount of exhaust energy received by the turbine, by rotating the compressor by operating the electric motor.

  In addition to such a supercharger, a high-pressure EGR device that connects an exhaust passage upstream of the turbine and an intake passage downstream of the compressor and recirculates part of the exhaust gas as high-pressure EGR gas to the internal combustion engine is provided. There is a case. According to the high-pressure EGR device, high-pressure EGR gas can be supplied to the internal combustion engine, and generation of NOx in the internal combustion engine can be suppressed.

  However, in the case of an internal combustion engine equipped with such a supercharger and a high pressure EGR device, the exhaust pressure upstream of the turbine changes depending on the degree of opening and closing of the variable nozzle. Particularly in the transient state of the internal combustion engine, the variable nozzle is closed to increase the supercharging pressure, so that the exhaust pressure upstream of the turbine rises. After the closing operation of the variable nozzle, there is a time lag until the turbo rotation speed increases and the boost pressure rises, so the differential pressure at the portion where the high pressure EGR gas enters and exits the high pressure EGR device temporarily increases. . As a result, the amount of high-pressure EGR gas recirculated to the internal combustion engine may increase, and smoke may deteriorate.

  Therefore, when the high pressure EGR gas is recirculated and the internal combustion engine is in a transient state, there is a technique for controlling the supercharging pressure of the supercharger by prohibiting the variable nozzle closing operation and operating the electric motor. It is disclosed (for example, see Patent Document 1). According to the technique of Patent Document 1, since the supercharging pressure is controlled by prohibiting the closing operation of the variable nozzle and operating the electric motor, the supercharging pressure can be increased without increasing the exhaust pressure. As a result, the amount of high-pressure EGR gas is not increased in a transient state of the internal combustion engine, and smoke is not deteriorated.

JP 2006-299892 A JP 2008-155101 A JP 2007-205306 A JP 2006-076604 A JP 2009-228479 A JP 2003-239755 A

However, in the technique of Patent Document 1, if the variable nozzle is kept constant by operating the electric motor in a state where the high pressure EGR gas is recirculated, the differential pressure at the portion where the high pressure EGR gas enters and exits the high pressure EGR device. Decreases and the amount of high-pressure EGR gas recirculated to the internal combustion engine becomes insufficient. Also, if the electric motor is operated and the variable nozzle is closed while the high pressure EGR gas is recirculated, the turbo efficiency is deteriorated, the pump loss is increased, and the fuel efficiency is improved even though the electric motor is operated. It can no longer be obtained.

  An object of the present invention is to provide a technique for improving fuel efficiency while obtaining a desired amount of EGR gas.

In the present invention, the following configuration is adopted. That is, the present invention
An excess of intake air taken into the internal combustion engine using a turbine disposed in the exhaust passage of the internal combustion engine and a compressor disposed in the intake passage of the internal combustion engine using exhaust energy discharged from the internal combustion engine A supercharger for feeding,
A variable nozzle that opens and closes to change the flow rate of the exhaust gas blown to the turbine; and
An electric motor for driving the compressor;
A low pressure EGR device that connects the exhaust passage downstream of the turbine and the intake passage upstream of the compressor, and recirculates a part of the exhaust gas as low pressure EGR gas to the intake passage;
When the low pressure EGR device is used to recirculate the low pressure EGR gas and control the target boost pressure, the compressor is driven auxiliary by the electric motor and the variable driving force increases as the auxiliary driving force of the electric motor increases. A control unit for opening the nozzle;
An internal combustion engine characterized by comprising:

  Since the low-pressure EGR gas is supplied to the intake passage in accordance with the intake pressure upstream of the compressor, the amount of the low-pressure EGR gas does not change regardless of the supercharging pressure even if the compressor is driven auxiliary by an electric motor. Therefore, in the present invention, when the low pressure EGR gas is recirculated and controlled to the target supercharging pressure, the compressor is auxiliary driven by the electric motor, and the variable nozzle is opened as the auxiliary driving force by the electric motor increases. . According to this, it is possible to control the target supercharging pressure with the electric motor while obtaining a desired low-pressure EGR gas amount. Furthermore, since the exhaust nozzle upstream of the turbine is not increased by the variable nozzle that has been opened, pump loss can be reduced, thereby improving fuel efficiency.

  When the low-pressure EGR gas is recirculated by the low-pressure EGR device and the engine load of the internal combustion engine is an extremely light load, the control unit fixes the variable nozzle, and the electric motor drives the compressor. It is preferable to boost the boost pressure by driving the auxiliary.

  Here, the extremely light load means that when the low pressure EGR gas is recirculated and controlled to the target supercharging pressure, the compressor is auxiliary driven by the electric motor, and the variable nozzle is increased as the auxiliary driving force by the electric motor becomes larger. When the opening operation is performed, the variable nozzle is opened too much and the turbo efficiency and the fuel consumption deteriorate.

  According to the present invention, it is possible to avoid deterioration of turbo efficiency and fuel consumption due to excessive opening of the variable nozzle in the case of an extremely light load.

The present invention also provides
An excess of intake air taken into the internal combustion engine using a turbine disposed in the exhaust passage of the internal combustion engine and a compressor disposed in the intake passage of the internal combustion engine using exhaust energy discharged from the internal combustion engine A supercharger for feeding,
A variable nozzle that opens and closes to change the flow rate of the exhaust gas blown to the turbine; and
An electric motor for driving the compressor;
A low pressure EGR device that connects the exhaust passage downstream of the turbine and the intake passage upstream of the compressor, and recirculates a part of the exhaust gas as low pressure EGR gas to the intake passage;
An internal combustion engine control method comprising:
When the low pressure EGR device is used to recirculate the low pressure EGR gas and control the target boost pressure, the compressor is driven auxiliary by the electric motor and the variable driving force increases as the auxiliary driving force of the electric motor increases. A control method for an internal combustion engine, wherein a nozzle is opened.

  Also according to the present invention, it is possible to control the target supercharging pressure with an electric motor while obtaining a desired low-pressure EGR gas amount. Furthermore, since the exhaust nozzle upstream of the turbine is not increased by the variable nozzle that has been opened, pump loss can be reduced, thereby improving fuel efficiency.

  According to the present invention, fuel efficiency can be improved while obtaining a desired amount of EGR gas.

1 is a diagram illustrating a schematic configuration of an internal combustion engine according to Embodiment 1 of the present invention. It is the figure which contrasted the case where an electric motor is driven and a supercharging pressure is raised, and the case where a variable nozzle is opened by maintaining (equal supercharging) which is the 1st control which concerns on a present Example. . 3 is a flowchart illustrating an EGR operation control routine according to the first embodiment.

  Specific examples of the present invention will be described below.

<Example 1>
(Internal combustion engine)
FIG. 1 is a diagram showing a schematic configuration of an internal combustion engine according to Embodiment 1 of the present invention. An internal combustion engine 1 shown in FIG. 1 is a water-cooled four-stroke cycle diesel engine having four cylinders. The internal combustion engine 1 is mounted on a vehicle. Each cylinder 2 is provided with a fuel injection valve 3. The fuel injection valve 3 is supplied with fuel such as light oil pumped up from a fuel tank by a supply pump and whose fuel injection pressure is determined by a common rail, and injects the fuel into the cylinder 2 at an appropriate amount and at an appropriate timing.

  An intake passage 4 is connected to the internal combustion engine 1. In the middle of the intake passage 4 connected to the internal combustion engine 1, a compressor 5a of a turbocharger 5 is disposed as a supercharger that operates using exhaust energy as a drive source. A first throttle valve 6 that adjusts the amount of fresh air flowing through the intake passage 4 is disposed in the intake passage 4 upstream of the compressor 5a. An air cleaner 7 is disposed in the intake passage 4 upstream of the first throttle valve 6. The air cleaner 7 removes dust and dirt in fresh air sucked into the internal combustion engine 1. An intercooler 8 that performs heat exchange between the intake air and the outside air is disposed in the intake passage 4 downstream of the compressor 5a. A second throttle valve 9 that adjusts the amount of intake air flowing through the intake passage 4 is disposed in the intake passage 4 downstream of the intercooler 8. The intake passage 4 and the devices arranged in the intake passage 4 constitute an intake system of the internal combustion engine 1.

  On the other hand, an exhaust passage 10 is connected to the internal combustion engine 1. In the middle of the exhaust passage 10 connected to the internal combustion engine 1, a turbine 5b of the turbocharger 5 is disposed. An oxidation catalyst 11 is disposed in the exhaust passage 10 downstream of the turbine 5b. A DPF 12 is disposed in the exhaust passage 10 downstream of the oxidation catalyst 11. The DPF 12 collects PM (Particulate matter) in the exhaust gas flowing through the exhaust passage 10. The DPF 12 carries an NOx storage reduction catalyst. The exhaust passage 10 and the devices arranged in the exhaust passage 10 constitute an exhaust system of the internal combustion engine 1.

  Here, the turbocharger 5 is a variable nozzle turbocharger with an electric motor. The turbocharger 5 includes a turbine 5b disposed in the exhaust passage 10, a compressor 5a disposed in the intake passage 4, a motor 13 attached to a rotary shaft between the turbine 5b and the compressor 5a, and driving the compressor 5a. And a variable nozzle 14 that opens and closes so as to change the flow rate of the exhaust gas blown to the turbine 5b. The turbine 5b and the compressor 5a are integrally connected by a rotating shaft, and the compressor 5a uses the energy of the exhaust gas discharged from the internal combustion engine 1 and input to the turbine 5b to supercharge the intake air taken into the internal combustion engine. . Further, when the electric motor 13 is driven, the rotating shaft can be forcibly rotated, and thereby the compressor 5a can be forcibly driven.

  The internal combustion engine 1 is provided with a low pressure EGR device 15 that recirculates (refluxs) part of the exhaust gas flowing through the exhaust passage 10 to the intake passage 4 at a low pressure. The exhaust gas recirculated by the low pressure EGR device 15 is referred to as low pressure EGR gas. The low-pressure EGR device 15 includes a low-pressure EGR passage 16 through which low-pressure EGR gas flows, a low-pressure EGR valve 17 that adjusts the amount of low-pressure EGR gas through the low-pressure EGR passage 16, and low-pressure EGR gas through the low-pressure EGR passage 16. A low pressure EGR cooler 18 for cooling the temperature. The low pressure EGR passage 16 connects the exhaust passage 10 downstream of the DPF 12 and the intake passage 4 upstream of the compressor 5 a and downstream of the first throttle valve 6. Through this low pressure EGR passage 16, the exhaust gas is sent as low pressure EGR gas to the internal combustion engine 1 at a low pressure. The low pressure EGR valve 17 is disposed in the low pressure EGR passage 16 and adjusts the amount of the low pressure EGR gas flowing through the low pressure EGR passage 16 by adjusting the passage sectional area of the low pressure EGR passage 16. In addition to the low pressure EGR valve 17, the amount of the low pressure EGR gas can also be adjusted by adjusting the first throttle valve 6. The low-pressure EGR cooler 18 is disposed in the low-pressure EGR passage 16 upstream of the low-pressure EGR valve 17 and exchanges heat between the low-pressure EGR gas passing through the low-pressure EGR cooler 18 and the engine coolant of the internal combustion engine 1 to Reduce the temperature of the EGR gas.

  The internal combustion engine 1 configured as described above is provided with an ECU (electronic control unit) 19 for controlling the internal combustion engine 1. The ECU 19 is a unit that controls the operation state of the internal combustion engine 1 in accordance with the operation conditions of the internal combustion engine 1 and the request of the driver. Various sensors such as a crank position sensor 20 and an accelerator position sensor 21 are connected to the ECU 19 via electric wiring, and output signals of these various sensors are input to the ECU 19. On the other hand, the fuel injection valve 3, the first throttle valve 6, the second throttle valve 9, the motor 13, the variable nozzle 14, and the low-pressure EGR valve 17 are connected to the ECU 19 via electric wiring. By controlling these devices. The ECU 19 receives the output signals from the crank position sensor 20, the accelerator position sensor 21, etc., determines the operating state of the internal combustion engine 1, and electrically controls the internal combustion engine 1 and the above devices based on the determined operating state.

(EGR operation control)
In this embodiment, the amount of low pressure EGR gas is controlled using the low pressure EGR valve 17 in accordance with the operating state of the internal combustion engine 1. As a result, a so-called EGR operation is performed in which the low-pressure EGR gas is included in the intake air sucked into the internal combustion engine 1, so that the oxygen concentration in the intake air is reduced to reduce the combustion temperature and the combustion speed. Thus, the effect of reducing NOx generated during combustion is exhibited.

Here, the electric motor 13 of the turbocharger 5 may be operated in the EGR operation state. For example, the deceleration energy of the vehicle on which the internal combustion engine 1 is mounted is regenerated by an alternator, and the electric motor 13 of the turbocharger 5 is operated by the regenerated electric power. As a case where the electric motor 13 is operated in such an EGR operation state, conventionally, there is a case where the high-pressure EGR gas is recirculated by a high-pressure EGR device that connects an exhaust passage upstream of the turbine and an intake passage downstream of the compressor. is there. However, if the electric motor is operated and the variable nozzle is kept constant while the high pressure EGR gas is recirculated, the differential pressure at the portion where the high pressure EGR gas enters and exits the high pressure EGR device decreases, and the internal combustion engine The amount of high-pressure EGR gas that is recirculated is insufficient. Also, if the electric motor is operated and the variable nozzle is closed while the high pressure EGR gas is recirculated, the turbo efficiency is deteriorated, the pump loss is increased, and the fuel efficiency is improved even though the electric motor is operated. It can no longer be obtained.

  Therefore, in this embodiment, when the low-pressure EGR gas is recirculated by the low-pressure EGR device 15 and controlled to the target supercharging pressure, the compressor 5a is driven auxiliary by the electric motor 13 and auxiliary driving by the electric motor 13 is performed. The variable nozzle 14 was opened as the force increased. This control is called the first control, and the ECU 19 that performs the first control corresponds to the control unit of the present invention.

  Since the low-pressure EGR gas is supplied to the intake passage 4 in accordance with the intake pressure upstream of the compressor 5a, the amount of the low-pressure EGR gas changes regardless of the supercharging pressure even if the compressor 5a is driven auxiliary by the electric motor 13. Absent. Therefore, when the first control as in the present embodiment is performed, the motor 13 can be controlled to the target supercharging pressure while obtaining a desired low-pressure EGR gas amount. Furthermore, since the variable nozzle 14 that has been opened does not increase the exhaust pressure upstream of the turbine 5b, it is possible to reduce pump loss and thereby improve fuel efficiency.

  FIG. 2 shows a case where the motor is driven to increase the supercharging pressure (B) and a case where the variable nozzle is opened while maintaining the target supercharging pressure which is the first control according to this embodiment (equal supercharging). It is the figure which contrasted with (A). As shown in FIG. 2A, when the supercharging pressure of B is increased, the fuel consumption rate is not reduced even if the driving force of the electric motor 13 is increased. On the other hand, when the variable nozzle 14 is opened with the equal supercharging of A, the fuel consumption rate decreases as the driving force of the electric motor 13 increases. Further, as shown in FIG. 2B, when the supercharging pressure of B is increased, the opening degree of the variable nozzle 14 is kept constant even when the driving force of the electric motor 13 is increased. On the other hand, when the variable nozzle 14 is opened by the equal supercharging of A, when the driving force of the electric motor 13 is increased, the variable nozzle 14 is opened by a large opening amount in proportion thereto. Further, as shown in FIG. 2C, when the supercharging pressure of B is increased, the supercharging pressure (intake manifold pressure) increases as the driving force of the electric motor 13 increases. On the other hand, when the variable nozzle 14 is opened by the equal supercharging of B, the supercharging pressure (in manifold pressure) is maintained even if the driving force of the electric motor 13 increases. When increasing the supercharging pressure of B, since the variable nozzle 14 is not opened even when the driving force of the electric motor 13 increases, the exhaust pressure (exhaust manifold pressure) also increases in the same way as the supercharging pressure. The pump loss is kept almost constant. On the other hand, when the variable nozzle 14 is opened with the equal supercharging of A, the variable nozzle 14 is opened when the driving force of the electric motor 13 is increased, so that the exhaust pressure (exhaust manifold pressure) decreases and the pump loss occurs. Decreases. Further, as shown in FIG. 2 (d), when the boost pressure of B is increased, the fuel consumption rate in FIG. 2 (a) is not significantly reduced even when the driving force of the electric motor 13 is increased. Since the pump loss in (c) is almost constant, the fuel efficiency improvement rate is only slightly increased. On the other hand, when the variable nozzle 14 is opened by the equal supercharging of A, when the driving force of the electric motor 13 is increased, the fuel consumption rate in FIG. 2 (a) is reduced and the pump loss in FIG. 2 (c) is further reduced. As a result, the fuel efficiency improvement rate will rise significantly. As described above, according to this embodiment, it is possible to improve fuel efficiency while obtaining a desired amount of EGR gas. In this embodiment, no high pressure EGR device is provided. This is because the fuel efficiency improvement effect by the first control is higher than when the high-pressure EGR device is installed. Therefore, the internal combustion engine 1 according to the present embodiment does not have a high-pressure EGR device, and simplification of the configuration and simplification of control during EGR operation can be achieved.

On the other hand, in the first control, there is a load in which the variable nozzle 14 opens too much and the turbo efficiency and fuel consumption deteriorate. This load is a case where the engine load of the internal combustion engine 1 is an extremely light load. Here, the extremely light load means that when the low-pressure EGR gas is recirculated and controlled to the target supercharging pressure, the compressor 5a is supplementarily driven by the electric motor 13, and the auxiliary driving force by the electric motor 13 is increased. When the variable nozzle 14 is opened, the variable nozzle 14 opens too much and the turbo efficiency and fuel consumption deteriorate.

  Therefore, when the low-pressure EGR gas is recirculated by the low-pressure EGR device 15 and the engine load of the internal combustion engine 1 is an extremely light load, the variable nozzle 14 is fixed and the electric motor 13 assists the compressor 5a. To boost the boost pressure. This control is referred to as second control, and the ECU 19 that performs the second control corresponds to the control unit of the present invention.

  Even if the first control is performed in the case of an extremely light load, the variable nozzle 14 opens too much and the turbo efficiency and fuel consumption deteriorate, so the second control is performed. Thereby, it can avoid that the variable nozzle 14 opens too much and turbo efficiency and fuel consumption deteriorate. Note that performing either the first control or the second control in this way means that the first control and the second control are selected according to the engine load of the internal combustion engine 1.

(EGR operation control routine)
The EGR operation control routine in the ECU 19 will be described based on the flowchart shown in FIG. FIG. 3 is a flowchart showing an EGR operation control routine. This routine is repeatedly executed by the ECU 19 every predetermined time. The ECU 19 that executes this routine corresponds to the control unit of the present invention.

  When the routine shown in FIG. 3 is started, in S101, it is determined whether or not the EGR operation is being performed. If it is determined in S101 that the EGR operation is being performed, the process proceeds to S102. On the other hand, if it is determined in S101 that the EGR operation is not being performed, this routine is temporarily terminated.

  In S102, it is determined whether or not the remaining amount of battery mounted on the vehicle is greater than or equal to a predetermined amount. In S102, when an affirmative determination is made that the remaining battery level is equal to or greater than the predetermined amount, the process proceeds to S103. On the other hand, if it is determined in S102 that the remaining battery level is less than the predetermined amount, this routine is temporarily terminated, for example, when the deceleration energy of the vehicle on which the internal combustion engine 1 is mounted is regenerated by the alternator. The regenerative energy is not used for the electric motor 13 but is used for charging the battery.

  In S103, the electric motor 13 is turned on to determine whether or not the electric motor 13 can drive the compressor 5a in an auxiliary manner. The state where the electric motor 13 cannot be turned on is, for example, when the deceleration energy of the vehicle on which the internal combustion engine 1 is mounted is regenerated by the alternator, and the regenerative energy is preferentially used for devices other than the electric motor 13. . If it is determined in S103 that the electric motor 13 can be turned on, the process proceeds to S104. On the other hand, if it is determined in S103 that the electric motor 13 cannot be turned on, this routine is temporarily terminated.

  In S104, it is determined whether or not the engine load of the internal combustion engine 1 corresponds to an extremely light load. Whether or not it corresponds to an extremely light load is determined from the operating state of the internal combustion engine 1 calculated by receiving output signals from the crank position sensor 20, the accelerator position sensor 21, and the like. If it is determined in S104 that the load is not an extremely light load, the process proceeds to S105. On the other hand, if it is determined in S104 that the load is extremely light, the process proceeds to S106.

  In S105, the compressor 5a is driven auxiliary by the electric motor 13, and the first control is performed to open the variable nozzle 14 as the auxiliary driving force of the electric motor 13 increases. After the processing of this step, this routine is once ended.

  In S106, while the variable nozzle 14 is fixed, the 2nd control which raises a supercharging pressure by driving the compressor 5a supplementarily with the electric motor 13 is implemented. After the processing of this step, this routine is once ended.

  In this routine described above, the first control and the second control can be selected according to the engine load of the internal combustion engine 1. Thereby, fuel consumption can be improved as an effect of operating the electric motor 13 while obtaining a desired low-pressure EGR gas amount.

<Others>
The internal combustion engine according to the present invention is not limited to the above-described embodiments, and various modifications may be made without departing from the gist of the present invention. Further, the above embodiment is not only an internal combustion engine but also an embodiment of a control method for the internal combustion engine.

1: internal combustion engine, 2: cylinder, 3: fuel injection valve, 4: intake passage, 5: turbocharger, 5a: compressor, 5b: turbine, 6: first throttle valve, 7: air cleaner, 8: intercooler, 9 : Second throttle valve, 10: exhaust passage, 11: oxidation catalyst, 12: DPF, 13: electric motor, 14: variable nozzle, 15: low pressure EGR device, 16: low pressure EGR passage, 17: low pressure EGR valve, 18: low pressure EGR cooler, 19: ECU, 20: crank position sensor, 21: accelerator position sensor

Claims (3)

An excess of intake air taken into the internal combustion engine using a turbine disposed in the exhaust passage of the internal combustion engine and a compressor disposed in the intake passage of the internal combustion engine using exhaust energy discharged from the internal combustion engine A supercharger for feeding,
A variable nozzle that opens and closes to change the flow rate of the exhaust gas blown to the turbine; and
An electric motor for driving the compressor;
A low pressure EGR device that connects the exhaust passage downstream of the turbine and the intake passage upstream of the compressor, and recirculates a part of the exhaust gas as low pressure EGR gas to the intake passage;
When the low pressure EGR device is used to recirculate the low pressure EGR gas and control the target boost pressure, the compressor is driven auxiliary by the electric motor and the variable driving force increases as the auxiliary driving force of the electric motor increases. A control unit for opening the nozzle;
An internal combustion engine comprising:   When the low-pressure EGR gas is recirculated by the low-pressure EGR device and the engine load of the internal combustion engine is an extremely light load, the control unit fixes the variable nozzle, and the electric motor drives the compressor. The internal combustion engine according to claim 1, wherein the boost pressure is increased by driving the engine auxiliary. An excess of intake air taken into the internal combustion engine using a turbine disposed in the exhaust passage of the internal combustion engine and a compressor disposed in the intake passage of the internal combustion engine using exhaust energy discharged from the internal combustion engine A supercharger for feeding,
A variable nozzle that opens and closes to change the flow rate of the exhaust gas blown to the turbine; and
An electric motor for driving the compressor;
A low pressure EGR device that connects the exhaust passage downstream of the turbine and the intake passage upstream of the compressor, and recirculates a part of the exhaust gas as low pressure EGR gas to the intake passage;
An internal combustion engine control method comprising:
When the low pressure EGR device is used to recirculate the low pressure EGR gas and control the target boost pressure, the compressor is driven auxiliary by the electric motor and the variable driving force increases as the auxiliary driving force of the electric motor increases. A control method for an internal combustion engine, wherein the nozzle is opened.

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