JP2008002350A - Exhaust gas recirculation device for internal combustion engine - Google Patents

Abstract

In an exhaust gas recirculation device for an internal combustion engine, it is possible to reduce the amount of EGR gas immediately after an instruction to reduce the amount of EGR gas at the start of the vehicle, and to increase the ratio of fresh air flowing into the internal combustion engine, thereby suppressing the occurrence of engine stall. Provide the technology that makes it possible.
A turbocharger having a turbine disposed in an exhaust passage and a compressor disposed in an intake passage, a low pressure EGR passage, a high pressure EGR passage, a start intention determination means (S103), and a start intention determination means are provided in a vehicle. High pressure EGR that reduces the amount of low-pressure EGR gas that recirculates using the low-pressure EGR passage and recirculates using the high-pressure EGR passage, while maintaining the EGR rate in advance before starting the vehicle. EGR gas amount control means (S104) for increasing the gas amount.
[Selection] Figure 2

Description

  The present invention relates to an exhaust gas recirculation device for an internal combustion engine.

A low-pressure EGR passage that takes in a part of the exhaust gas from an exhaust passage downstream of the turbine as low-pressure exhaust gas recirculation (hereinafter referred to as EGR) gas and returns the low-pressure EGR gas to an intake passage upstream of the compressor, and an upstream of the turbine A high-pressure EGR passage that takes in part of the exhaust gas from the exhaust passage as high-pressure EGR gas and recirculates the high-pressure EGR gas to the intake passage downstream of the compressor, and according to the engine speed and the engine load, Or the technique which switches EGR using a high voltage | pressure EGR channel | path is known (for example, refer patent document 1).
JP 2004-150319 A Japanese Patent Laid-Open No. 02-185652 JP 2002-147290 A

  By the way, in an internal combustion engine mounted on a vehicle, the engine rotation speed may decrease when the vehicle starts. If the EGR gas flows into the internal combustion engine when the engine rotation speed decreases when the vehicle starts, the oxygen concentration in the cylinder decreases and the explosive force decreases. As a result, an engine stall may occur.

  Therefore, in order to suppress engine stall when the vehicle starts, it is common practice to reduce the amount of low-pressure EGR gas from the low-pressure EGR passage when the vehicle starts.

  Here, the path through which the low-pressure EGR gas flows has a long path length, a large capacity in the middle, and a large amount of low-pressure EGR gas present in an intake passage on the path. For this reason, even when an instruction to reduce the amount of low-pressure EGR gas is given, the low-pressure EGR gas existing on the passage through which the low-pressure EGR gas flows is recirculated to the internal combustion engine for a while after the instruction, and the amount of low-pressure EGR gas cannot be reduced. Therefore, it is not possible to increase the fresh air ratio of the gas flowing into the internal combustion engine immediately after the low pressure EGR gas reduction instruction.

  For this reason, engine stall may occur due to the large amount of EGR gas still flowing into the internal combustion engine for a while immediately after the low pressure EGR gas reduction instruction at the start of the vehicle.

  The present invention has been made in view of the above circumstances, and an object of the present invention is to allow an exhaust gas recirculation device for an internal combustion engine to reduce the amount of EGR gas immediately after an instruction to reduce the amount of EGR gas when starting the vehicle, and to flow into the internal combustion engine. An object of the present invention is to provide a technology that can increase the ratio of fresh air to be generated and suppress the occurrence of engine stall.

In the present invention, the following configuration is adopted. That is,
A turbocharger having a turbine disposed in an exhaust passage of an internal combustion engine mounted on a vehicle and a compressor disposed in an intake passage of the internal combustion engine;
A low pressure EGR passage that takes a part of the exhaust gas as a low pressure EGR gas from the exhaust passage downstream of the turbine and recirculates the low pressure EGR gas to an intake passage upstream of the compressor;
A high-pressure EGR passage that takes a part of exhaust gas as a high-pressure EGR gas from an exhaust passage upstream of the turbine and recirculates the high-pressure EGR gas to an intake passage downstream of the compressor;
Starting intention determination means for determining whether or not the vehicle has an intention to start;
When the start intention determination means determines that the vehicle has an intention to start, the low pressure EGR gas flowing back using the low pressure EGR passage is reduced and the high pressure is maintained while maintaining the EGR rate before starting the vehicle. EGR gas amount control means for increasing the amount of high-pressure EGR gas that recirculates using the EGR passage;
An exhaust gas recirculation device for an internal combustion engine.

  In the present invention, when it is determined that the vehicle has an intention to start, the low-pressure EGR gas that is recirculated using the low-pressure EGR passage is reduced and the high-pressure EGR passage is used while maintaining the EGR rate in advance before starting the vehicle. The amount of high-pressure EGR gas that is refluxed is increased.

  Here, the route through which the high-pressure EGR gas flows is short, and the amount of high-pressure EGR gas existing on the route is small. For this reason, when instructing the reduction of the high-pressure EGR gas, the high-pressure EGR gas is difficult to be recirculated to the internal combustion engine immediately after the reduction instruction, and the amount of the high-pressure EGR gas can be reduced. Can increase the rate of fresh air.

  Therefore, according to the present invention, before starting the vehicle, the low pressure EGR gas that cannot be reduced immediately after the reduction instruction is reduced, and the high pressure EGR gas that can be reduced is increased immediately after the reduction instruction. . As a result, the high pressure EGR gas amount can be reduced immediately after the EGR gas reduction instruction at the start of the vehicle, and the fresh air ratio of the gas flowing into the internal combustion engine can be increased, so that the engine stall can be suppressed.

  The EGR gas amount control means performs control to maintain the EGR rate, decrease the amount of low-pressure EGR gas recirculated using the low-pressure EGR passage, and increase the amount of high-pressure EGR gas recirculated using the high-pressure EGR passage. If the engine speed of the internal combustion engine falls below a predetermined speed, the amount of high-pressure EGR gas that is recirculated using the high-pressure EGR passage may be reduced.

  Here, if the EGR gas flows into the internal combustion engine when the engine speed at the start of the vehicle is lower than a predetermined speed, the oxygen concentration in the cylinder is lowered and the explosive force is lowered. As a result, an engine stall may occur. The predetermined speed means that if the engine speed at the start of the vehicle is lower than this speed and the EGR gas is flowing into the internal combustion engine, the oxygen concentration in the cylinder will decrease, the explosive power will decrease, and the engine stall will It is the speed that can happen.

  However, according to the present invention, when the engine speed of the internal combustion engine falls below a predetermined speed, the amount of high-pressure EGR gas that is recirculated using the high-pressure EGR passage is reduced. Is reduced, the ratio of fresh air flowing into the internal combustion engine is increased, and engine stall is suppressed.

  According to the present invention, in an exhaust gas recirculation device for an internal combustion engine, an engine stall occurs because the EGR gas amount can be reduced immediately after the EGR gas reduction instruction is given at the start of the vehicle, and the fresh air ratio of the gas flowing into the internal combustion engine can be increased. Can be suppressed.

  Specific examples of the present invention will be described below.

<Example 1>
FIG. 1 is a diagram showing a schematic configuration of an internal combustion engine to which the exhaust gas recirculation apparatus for an internal combustion engine according to this embodiment is applied and its intake / exhaust system.

  An internal combustion engine 1 shown in FIG. 1 is a water-cooled four-cycle diesel engine having four cylinders 2. The internal combustion engine 1 is mounted on a vehicle.

  An intake passage 3 is connected to the internal combustion engine 1. A compressor housing 5 a of a turbocharger 5 that operates using exhaust energy as a drive source is disposed in the intake passage 3. A first throttle 6 for adjusting the flow rate of intake air flowing through the intake passage 3 is disposed in the intake passage 3 upstream of the compressor housing 5a. The first throttle 6 is opened and closed by an electric actuator. An air flow meter 7 that outputs a signal corresponding to the flow rate of the intake air flowing through the intake passage 3 is disposed in the intake passage 3 upstream of the first throttle 6. The air flow meter 7 measures the intake air amount of 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 3 downstream of the compressor housing 5a. A second throttle 9 for adjusting the flow rate of the intake air flowing through the intake passage 3 is disposed in the intake passage 3 downstream of the intercooler 8. The second throttle 9 is opened and closed by an electric actuator.

  On the other hand, an exhaust passage 4 is connected to the internal combustion engine 1. In the middle of the exhaust passage 4, a turbine housing 5b of the turbocharger 5 is disposed. A particulate filter (hereinafter simply referred to as a filter) 10 is disposed in the exhaust passage 4 downstream of the turbine housing 5b. The filter 10 carries an NOx storage reduction catalyst (hereinafter simply referred to as NOx catalyst). The filter 10 collects particulate matter in the exhaust gas. Further, the NOx catalyst occludes nitrogen oxide (NOx) in the exhaust gas when the oxygen concentration of the exhaust gas flowing into the NOx catalyst is high, and on the other hand, when the oxygen concentration of the exhaust gas flowing into the NOx catalyst decreases. Releases the stored NOx. At that time, if a reducing component such as hydrocarbon (HC) or carbon monoxide (CO) is present in the exhaust, NOx released from the NOx catalyst is reduced. Note that an oxidation catalyst or a three-way catalyst may be supported on the filter 10 instead of the NOx catalyst.

  The internal combustion engine 1 is provided with a low pressure EGR device 30 that recirculates (recirculates) part of the exhaust gas flowing through the exhaust passage 4 to the intake passage 3 at a low pressure. The low pressure EGR device 30 includes a low pressure EGR passage 31, a low pressure EGR valve 32, and an EGR cooler 33.

  The low pressure EGR passage 31 connects the exhaust passage 4 downstream of the filter 10 and the intake passage 3 upstream of the compressor housing 5 a and downstream of the first throttle 6. Through this low-pressure EGR passage 31, the exhaust gas is recirculated to the internal combustion engine at a low pressure. In this embodiment, the exhaust gas recirculated through the low pressure EGR passage 31 is referred to as low pressure EGR gas.

  Further, the low pressure EGR valve 32 adjusts the amount of the low pressure EGR gas flowing through the low pressure EGR passage 31 by adjusting the passage sectional area of the low pressure EGR passage 31. Further, the EGR cooler 33 exchanges heat between the low-pressure EGR gas passing through the EGR cooler 33 and the cooling water of the internal combustion engine 1 to lower the temperature of the low-pressure EGR gas.

  The internal combustion engine 1 is provided with a high-pressure EGR device 40 that recirculates a part of the exhaust gas flowing through the exhaust passage 4 to the intake passage 3 at a high pressure. The high pressure EGR device 40 includes a high pressure EGR passage 41 and a high pressure EGR valve 42.

The high pressure EGR passage 41 connects the exhaust passage 4 upstream of the turbine housing 5 b and the intake passage 3 downstream of the second throttle 9. Through this high-pressure EGR passage 41, the exhaust gas is recirculated to the internal combustion engine at a high pressure. In this embodiment, the exhaust gas recirculated through the high pressure EGR passage 41 is referred to as high pressure EGR gas.

  Further, the high pressure EGR valve 42 adjusts the amount of high pressure EGR gas flowing through the high pressure EGR passage 41 by adjusting the passage sectional area of the high pressure EGR passage 41.

  The internal combustion engine 1 configured as described above is provided with an ECU 11 that is an electronic control unit for controlling the internal combustion engine 1. The ECU 11 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.

  Further, the ECU 11 outputs an electric signal corresponding to the amount of depression of the accelerator pedal 12 by the driver to detect an engine load, and an electric opening degree sensor 13 capable of detecting the engine load, and electric according to the amount of depression of the clutch pedal 14 by the driver. A clutch opening sensor 15 that outputs a signal and can detect the engagement / disengagement of the clutch, and a crank position sensor 16 that detects the engine rotational speed are connected via electric wiring, and output signals of these various sensors are input to the ECU 11. It is like that.

  On the other hand, the ECU 11 is connected to the first throttle 6, the second throttle 9, the low pressure EGR valve 32, and the high pressure EGR valve 42 through electric wiring, and these devices are controlled by the ECU 11.

  The amount of low-pressure EGR gas recirculated to the internal combustion engine 1 is adjusted by at least one of the low-pressure EGR valve 32 or the first throttle 6. Further, the amount of high pressure EGR gas recirculated to the internal combustion engine 1 is adjusted by at least one of the high pressure EGR valve 42 and the second throttle 9.

  By the way, in the internal combustion engine 1 mounted on the vehicle, the engine rotation speed may decrease when the vehicle starts. If the EGR gas flows into the internal combustion engine 1 when the engine rotational speed decreases when the vehicle starts, the oxygen concentration in the cylinder 2 decreases and the explosive force decreases. As a result, an engine stall may occur.

  Therefore, in order to suppress engine stall at the time of vehicle start, it is generally performed to reduce the amount of low-pressure EGR gas that is recirculated using the low-pressure EGR passage 31 at the time of vehicle start.

  Here, the path through which the low-pressure EGR gas flows is long because the path length is long and the intercooler 8 and the like are large, and the amount of low-pressure EGR gas present in the intake passage 3 and the intercooler 8 on the path is large. For this reason, even when the low pressure EGR gas is instructed to be reduced and the low pressure EGR valve 32 is moved to the closed side, the low pressure existing in the intake passage 3 or the intercooler 8 on the path through which the low pressure EGR gas flows for a while thereafter. Since the EGR gas is recirculated to the internal combustion engine 1 and the amount of low-pressure EGR gas cannot be reduced, the ratio of fresh air flowing into the internal combustion engine 1 immediately after the low-pressure EGR gas reduction instruction cannot be increased.

  For this reason, engine stall may occur because the amount of EGR gas still flowing into the internal combustion engine 1 is still large for a while after the instruction to reduce the amount of low-pressure EGR gas when the vehicle starts.

  Therefore, in this embodiment, when it is determined that the vehicle has an intention to start, the low-pressure EGR passage 31 is used for refluxing while maintaining the overall EGR rate of the gas flowing into the internal combustion engine 1 in advance before starting the vehicle. The amount of low-pressure EGR gas to be reduced is decreased, and the amount of high-pressure EGR gas to be recirculated using the high-pressure EGR passage 41 is increased.

Specifically, when the clutch pedal 14 is depressed and the clutch opening sensor 15 detects that the vehicle has an intention to start, the entire EG of the gas flowing into the internal combustion engine 1 before the vehicle starts.
Although the R ratio is maintained, as the recirculating EGR gas, the low pressure EGR valve 32 is moved to the close side and the high pressure EGR valve 42 so that the low pressure EGR gas amount decreases and the high pressure EGR gas amount increases. Move to the open side.

  Here, the route through which the high-pressure EGR gas flows is short, and the amount of high-pressure EGR gas existing on the route is small. For this reason, when instructing the reduction of the high-pressure EGR gas, the high-pressure EGR gas is hardly recirculated to the internal combustion engine 1 immediately after the reduction instruction, and the high-pressure EGR gas amount can be reduced, so that the high-pressure EGR gas flows into the internal combustion engine 1 immediately after the reduction instruction. It is possible to increase the ratio of fresh air to be generated.

  Therefore, according to the present embodiment, before starting the vehicle, the low pressure EGR gas that cannot be reduced immediately after the reduction instruction is reduced, and the high pressure EGR gas that can be reduced immediately after the reduction instruction is increased. Become. As a result, the high pressure EGR gas amount can be reduced immediately after the EGR gas reduction instruction at the start of the vehicle, and the fresh air ratio of the gas flowing into the internal combustion engine 1 can be increased, so that the engine stall can be suppressed.

  In this embodiment, while maintaining the overall EGR rate of the gas flowing into the internal combustion engine 1, the amount of low-pressure EGR gas that is recirculated using the low-pressure EGR passage 31 is reduced, and the recirculation is performed using the high-pressure EGR passage 41. During the execution of the control before starting the vehicle to increase the amount of the high-pressure EGR gas, when the vehicle actually starts and the engine speed of the internal combustion engine 1 falls below a predetermined speed when the vehicle starts, the low-pressure EGR passage 31 is opened. The amount of the high-pressure EGR gas to be recirculated is reduced using the high-pressure EGR passage 41 while the amount of the low-pressure EGR gas to be recirculated is kept as it is.

  Specifically, when the crank position sensor 16 detects that the engine speed of the internal combustion engine 1 at the start of the vehicle is lower than a predetermined speed, the low-pressure EGR gas amount remains small, and the high-pressure EGR gas amount also decreases. In this manner, the low pressure EGR valve 32 is kept closed and the high pressure EGR valve 42 is moved to the closed side.

  Here, if the EGR gas flows into the internal combustion engine 1 when the engine rotational speed of the internal combustion engine 1 at the time of starting the vehicle is lower than a predetermined speed, the oxygen concentration in the cylinder 2 is reduced and the explosive force is reduced. . As a result, an engine stall may occur.

  However, according to the present embodiment, when the engine speed of the internal combustion engine 1 falls below a predetermined speed, the amount of low-pressure EGR gas that is recirculated using the low-pressure EGR passage 31 is kept reduced, and the high-pressure EGR passage 41 is further reduced. Since the amount of the high-pressure EGR gas to be recirculated is reduced, immediately after the start of the control, the amount of the high-pressure EGR gas that has been recirculated in a large amount until then is reduced, and the amount of the EGR gas is reduced to flow into the internal combustion engine 1. Increases the rate of fresh air and suppresses engine stalls.

  Next, the flow of EGR gas supply control accompanying the vehicle start according to this embodiment will be described. FIG. 2 is a flowchart showing a flow of EGR gas supply control associated with vehicle start-up according to this embodiment. This routine is repeatedly executed every predetermined time.

  In step S101, the ECU 11 determines whether or not the internal combustion engine 1 is in an idling state. Whether the engine is idling or not is determined based on the engine load detected by the accelerator opening sensor 13, the engine speed detected by the crank position sensor 16, the intake air amount detected by the air flow meter 7, and the like. This is determined by determining whether the motor is driven with no load.

If it is determined in step S101 that the engine is not idling, the ECU 11 once ends this routine. If it is determined that the vehicle is idling,
Proceed to step S102.

  In step S102, the ECU 11 acquires a control value for the opening degree of the low pressure EGR valve 32 and a control value for the opening degree of the high pressure EGR valve 42. The opening degree of the low pressure EGR valve 32 and the opening degree of the high pressure EGR valve 42 are low pressures corresponding to the intake air amount detected by the air flow meter 7, the target EGR rate stored in the ROM of the ECU 11, and the engine speed and the engine load. Control is performed based on a target mixture ratio of the EGR gas and the high-pressure EGR gas. For this reason, the control value of the opening degree of the low-pressure EGR valve 32 and the control value of the opening degree of the high-pressure EGR valve 42 can be acquired by receiving the numerical value on the control.

  In step S103 following step S102, the ECU 11 detects whether or not the clutch pedal 14 is depressed. Thus, it is determined whether or not there is a vehicle start intention to start the vehicle by connecting the rotation of the crankshaft of the internal combustion engine 1 to the drive shaft. Whether or not the clutch pedal 14 is depressed is determined based on the clutch opening detected by the clutch opening sensor 15. The ECU 11 that executes this step corresponds to the start intention determination means of the present invention.

  If it is determined in step S103 that the clutch pedal 14 is not depressed, the ECU 11 once ends this routine. When it is determined that the clutch pedal 14 is depressed, the process proceeds to step S104.

  In step S104, the ECU 11 adjusts the opening degree of the low pressure EGR valve 32 so as to be smaller than the control value, and reduces the low pressure EGR gas amount. At the same time, the opening degree of the high pressure EGR valve 42 is adjusted to be larger than the control value to increase the amount of high pressure EGR gas. At this time, the target EGR rate of the gas flowing into the internal combustion engine 1 is maintained at the value in step S101.

  The amount by which the low pressure EGR gas amount is reduced or the amount by which the high pressure EGR gas amount is increased is set such that the predetermined correction amount is reduced or increased so as to maintain the target EGR rate. The opening degree of 42 may be adjusted, or the opening degree of the low pressure EGR valve 32 or the high pressure EGR valve 42 may be adjusted to a predetermined target opening degree so as to maintain the target EGR rate.

  Thus, in step S104, when there is a vehicle start intention before starting the vehicle, the low-pressure EGR gas that cannot be reduced immediately after the weight reduction instruction is reduced in advance, and the high pressure that can be reduced immediately after the weight reduction instruction. Increase the amount of EGR gas. As a result, the high pressure EGR gas amount can be reduced immediately after the EGR gas reduction instruction at the start of the vehicle, and the fresh air ratio of the gas flowing into the internal combustion engine 1 can be increased, so that the engine stall can be suppressed.

  In step S105 following step S104, the ECU 11 detects whether or not the depression of the clutch pedal 14 has been released. Thereby, it is determined whether or not the vehicle is started by connecting the rotation of the crankshaft of the internal combustion engine 1 to the drive shaft from a state in which the vehicle has an intention to start (that is, whether or not the vehicle has started). Whether or not the depression of the clutch pedal 14 has been released is determined based on the clutch opening detected by the clutch opening sensor 15.

  If it is determined in step S105 that the depression of the clutch pedal 14 has not been released, the ECU 11 returns to step S104 to form a loop until the vehicle starts to release the depression of the clutch pedal 14. If it is determined that the depression of the clutch pedal 14 has been released, the process proceeds to step S106.

In step S106, the ECU 11 acquires the engine rotational speed NE of the internal combustion engine 1. The engine rotational speed NE can be acquired from a detection value detected by the crank position sensor 16.

  In step S107 following step S106, the ECU 11 determines whether or not the engine speed NE of the internal combustion engine 1 is lower than the predetermined speed Ne1. The predetermined speed Ne1 is such that when the engine rotational speed NE at the time of starting the vehicle is lower than this speed and the EGR gas flows into the internal combustion engine 1, the oxygen concentration in the cylinder 2 decreases and the explosive power decreases. However, the speed is such that an engine stall may occur.

  If it is determined in step S107 that the engine speed NE does not fall below the predetermined speed Ne1, the ECU 11 once ends this routine. If it is determined that the engine speed NE is lower than the predetermined speed Ne1, the process proceeds to step S108.

  In step S108, the ECU 11 adjusts the opening degree of the high pressure EGR valve 42 so as to be smaller than the control value, and reduces the amount of high pressure EGR gas. Here, the opening degree of the low pressure EGR valve 32 is maintained in a state adjusted to be smaller than the control value in step S104, and the low pressure EGR gas amount is kept reduced.

  The amount by which the amount of high-pressure EGR gas is reduced may be adjusted by adjusting the opening degree of the high-pressure EGR valve 42 so as to reduce a predetermined correction amount, or the opening degree of the high-pressure EGR valve 42 may be set to a predetermined target. It may be adjusted to the opening.

  Thus, in step S108, when the engine speed NE of the internal combustion engine 1 at the start of the vehicle is lower than the predetermined speed Ne1, the amount of high-pressure EGR gas that recirculates using the high-pressure EGR passage 41 is reduced. Immediately after the start of this control, the amount of high-pressure EGR gas that has been recirculated in large quantities until then is decreased, and consequently the amount of EGR gas that recirculates to the internal combustion engine is decreased to increase the ratio of fresh air flowing into the internal combustion engine 1; Suppresses engine stall.

  In step S108, the high pressure EGR valve 42 may be controlled to be fully closed so that the high pressure EGR gas amount does not flow at all. By doing so, it is possible to further reduce the amount of EGR gas recirculated to the internal combustion engine and increase the fresh air ratio of the gas flowing into the internal combustion engine 1, thereby further suppressing the occurrence of engine stall.

  In this embodiment, the ECU 11 that executes the processes of steps S104 and S108 corresponds to the EGR gas amount control means in the present invention.

  In the flowchart of the present embodiment shown in FIG. 2, the opening degrees of the low pressure EGR valve 32 and the high pressure EGR valve 42 are adjusted in order to change the low pressure EGR gas amount and the high pressure EGR gas amount. Alternatively, the opening degree of the first throttle 6 and the second throttle 9 may be adjusted. In this case, by moving the first throttle 6 to the open side, the differential pressure between the exhaust passage 4 side and the intake passage 3 side of the low pressure EGR passage 31 is reduced, so that the amount of low pressure EGR gas can be reduced. Further, by moving the second throttle 9 to the closing side, the differential pressure between the exhaust passage 4 side and the intake passage 3 side of the high pressure EGR passage 41 is increased, so that the amount of high pressure EGR gas can be increased.

  In the above-described embodiment, the description has been given by taking as an example a vehicle including a clutch pedal of an MT vehicle. However, the present invention is not limited to this, and the present invention can also be applied to an AT vehicle by replacing the operation of the clutch pedal in the above embodiment with the operation of the brake pedal.

The exhaust gas recirculation apparatus for an 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.

1 is a diagram illustrating an internal combustion engine and an intake / exhaust system thereof according to Embodiment 1. FIG. 3 is a flowchart showing a flow of EGR gas supply control that accompanies vehicle start according to Embodiment 1;

Explanation of symbols

Reference Signs List 1 internal combustion engine 2 cylinder 3 intake passage 4 exhaust passage 5 turbocharger 5a compressor housing 5b turbine housing 6 first throttle 7 air flow meter 8 intercooler 9 second throttle 10 filter 12 accelerator pedal 13 accelerator opening sensor 14 clutch pedal 15 clutch open Degree sensor 16 Crank position sensor 30 Low pressure EGR device 31 Low pressure EGR passage 32 Low pressure EGR valve 33 EGR cooler 40 High pressure EGR device 41 High pressure EGR passage 42 High pressure EGR valve

Claims (2)

A turbocharger having a turbine disposed in an exhaust passage of an internal combustion engine mounted on a vehicle and a compressor disposed in an intake passage of the internal combustion engine;
A low pressure EGR passage that takes a part of the exhaust gas as a low pressure EGR gas from the exhaust passage downstream of the turbine and recirculates the low pressure EGR gas to an intake passage upstream of the compressor;
A high-pressure EGR passage that takes a part of exhaust gas as a high-pressure EGR gas from an exhaust passage upstream of the turbine and recirculates the high-pressure EGR gas to an intake passage downstream of the compressor;
Starting intention determination means for determining whether or not the vehicle has an intention to start;
When the start intention determination means determines that the vehicle has an intention to start, the low pressure EGR gas flowing back using the low pressure EGR passage is reduced and the high pressure is maintained while maintaining the EGR rate before starting the vehicle. EGR gas amount control means for increasing the amount of high-pressure EGR gas that recirculates using the EGR passage;
An exhaust gas recirculation device for an internal combustion engine, comprising: The EGR gas amount control means performs control to maintain the EGR rate, decrease the amount of low-pressure EGR gas recirculated using the low-pressure EGR passage, and increase the amount of high-pressure EGR gas recirculated using the high-pressure EGR passage. 2. The internal combustion engine according to claim 1, wherein when the engine rotational speed of the internal combustion engine is lower than a predetermined speed, the amount of high-pressure EGR gas that is recirculated using the high-pressure EGR passage is reduced. Exhaust gas recirculation device.

Images