JP-2026074700-A - Exhaust gas recirculation system

JP2026074700AJP 2026074700 AJP2026074700 AJP 2026074700AJP-2026074700-A

Abstract

[Problem] To enable the discharge of condensed water generated in the low-pressure EGR passage into the exhaust passage while suppressing a decrease in the NOx reduction effect contained in the exhaust. [Solution] The exhaust gas recirculation device 100 comprises a high-pressure EGR device 40, a low-pressure EGR device 50, and a control device 60. The high-pressure EGR device 40 has a high-pressure EGR passage 41 connected to the portion of the intake passage 13 downstream of the compressor 32. The low-pressure EGR device 50 has a low-pressure EGR passage 51 connected to the portion of the intake passage 13 upstream of the compressor 32. The control device 60 identifies the operating range of the internal combustion engine 10 and calculates the retention amount, which is an estimated value of the amount of condensed water accumulated in the low-pressure EGR passage 51. If the retention amount is greater than a determination value corresponding to the current operating range, the control device 60 operates the low-pressure EGR device 50 to reduce the return flow rate of the low-pressure EGR gas. [Selection Diagram] Figure 1

Inventors

高野雅臣
近末吉人

Assignees

トヨタ自動車株式会社
株式会社豊田自動織機

Dates

Publication Date: 20260507
Application Date: 20241021

Claims (4)

An exhaust gas recirculation device provided in an internal combustion engine comprising a cylinder, an intake passage through which air introduced into the cylinder flows, an exhaust passage through which exhaust gas discharged from the cylinder flows, and a supercharger for supercharging the air flowing through the intake passage, The supercharger comprises a turbine installed in the exhaust passage and a compressor installed in the intake passage and operating in sync with the turbine. The exhaust gas recirculation device is, A high-pressure EGR device that recirculates the exhaust gas flowing through the exhaust passage as high-pressure EGR gas into the intake passage, A low-pressure EGR device that recirculates the exhaust gas flowing through the exhaust passage as low-pressure EGR gas into the intake passage, The system includes a control device for controlling the high-pressure EGR device and the low-pressure EGR device in order to adjust the return flow rate of the high-pressure EGR gas and the return flow rate of the low-pressure EGR gas, The high-pressure EGR device has a high-pressure EGR passage, the first end of which is connected to the portion of the exhaust passage upstream of the turbine, and the second end of which is connected to the portion of the intake passage downstream of the compressor. The low-pressure EGR device is A low-pressure EGR passage, the first end of which is connected to the portion of the exhaust passage downstream of the turbine, and the second end of which is connected to the portion of the intake passage upstream of the compressor, The system includes a cooling device for cooling the low-pressure EGR gas flowing through the low-pressure EGR passage, The control device is Based on the output torque and engine rotational speed of the internal combustion engine, the operating range of the internal combustion engine is determined. The accumulation amount is calculated as an estimated value of the amount of condensed water remaining in the low-pressure EGR passage. An exhaust gas recirculation device that performs the following: when the amount of stagnant gas is greater than a determination value corresponding to the operating range, it operates the low-pressure EGR device to reduce the return flow rate of the low-pressure EGR gas.
The operating region includes a first operating region in which the recirculation of the high-pressure EGR gas into the intake passage is prohibited, and a second operating region in which both the high-pressure EGR gas and the low-pressure EGR gas are permitted to be recirculated into the intake passage. The exhaust gas recirculation device according to claim 1, wherein the determination value corresponding to the second operating region is smaller than the determination value corresponding to the first operating region.
The second operating region includes a third operating region and a fourth operating region in which, compared to the third operating region, the effect of improving exhaust characteristics by recirculating the low-pressure EGR gas into the intake passage is lower. The exhaust gas recirculation device according to claim 2, wherein the determination value corresponding to the fourth operating region is smaller than the determination value corresponding to the third operating region.
The control device is The amount of condensed water generated in the low-pressure EGR passage and the amount of condensed water discharged from the low-pressure EGR passage are estimated at predetermined control cycles. The amount of material left is derived by accumulating the difference between the amount of material generated and the amount of material discharged for each control cycle. The exhaust gas recirculation device according to any one of claims 1 to 3, wherein the control device calculates the discharge amount as the sum of the discharge amount of condensed water from the low-pressure EGR passage to the exhaust passage and the discharge amount of condensed water from the low-pressure EGR passage to the intake passage.

Description

This invention relates to an exhaust gas recirculation device installed in an internal combustion engine. The exhaust gas recirculation system disclosed in Patent Document 1 comprises a high-pressure EGR system, a low-pressure EGR system, and a control device. The high-pressure EGR system includes a high-pressure EGR passage that recirculates exhaust gas flowing through the exhaust passage of an internal combustion engine as high-pressure EGR gas into the intake passage of the internal combustion engine, and an adjustment valve that adjusts the recirculation rate of the high-pressure EGR gas. The high-pressure EGR passage is connected to the portion of the intake passage downstream of the turbocharger's compressor. The low-pressure EGR system comprises a low-pressure EGR passage that recirculates exhaust gas flowing through the exhaust passage into the intake passage as low-pressure EGR gas, a cooling device that cools the low-pressure EGR gas flowing through the low-pressure EGR passage, and an adjustment valve that adjusts the recirculation rate of the low-pressure EGR gas. The low-pressure EGR passage is connected to the portion of the intake passage upstream of the turbocharger's compressor. In the low-pressure EGR passage, condensation is generated as the cooling device cools the low-pressure EGR gas. If the flow velocity of the low-pressure EGR gas in the low-pressure EGR passage is high, the condensation flows along with the low-pressure EGR gas and is discharged into the intake passage. On the other hand, if the flow velocity of the low-pressure EGR gas in the low-pressure EGR passage is low, or if the flow of the low-pressure EGR gas in the low-pressure EGR passage has stopped, the condensation flows towards the first end of the low-pressure EGR passage due to its own gravity. This condensation is then discharged into the exhaust passage. If the estimated amount of condensed water accumulated in the low-pressure EGR passage exceeds a standard value, the control device activates the adjustment valves for the high-pressure EGR system and the low-pressure EGR passage to reduce the proportion of low-pressure EGR gas in the total amount of EGR gas recirculated to the intake passage. This allows the control device to reduce the amount of condensed water remaining in the low-pressure EGR passage by discharging it from the low-pressure EGR passage to the exhaust passage. Japanese Patent Publication No. 2012-163061 Figure 1 is a schematic diagram showing an internal combustion engine equipped with one embodiment of an exhaust gas recirculation device.Figure 2 shows the operating range of the internal combustion engine shown in Figure 1.Figure 3 shows the relationship between the multiple operating regions and the judgment values in Figure 2.Figure 4 is a flowchart showing a series of processes performed by the control device included in the exhaust gas recirculation system shown in Figure 1.Figure 5 is a block diagram showing the condensate calculation process. One embodiment of the exhaust gas recirculation device will be described with reference to Figures 1 to 5. <Configuration of an internal combustion engine> Figure 1 shows an internal combustion engine 10 equipped with an exhaust gas recirculation device 100. The internal combustion engine 10 is mounted in a vehicle. The internal combustion engine 10 comprises a plurality of cylinders 11, a crankshaft 12, an intake passage 13, a plurality of fuel injectors 14, and an exhaust passage 16. The intake passage 13 is the passage through which air flows to be introduced into the multiple cylinders 11. An intercooler 21 and a throttle valve 22 are installed in the intake passage 13. The intercooler 21 cools the air flowing through the intake passage 13. The throttle valve 22 is located downstream of the intercooler 21 in the intake passage 13. The amount of air introduced into the multiple cylinders 11 changes by adjusting the opening of the throttle valve 22. The fuel injector 14 injects fuel into the corresponding cylinder 11. A fuel-air mixture is burned within the multiple cylinders 11. This causes the crankshaft 12 to rotate. The combustion of the mixture also generates exhaust gas within the multiple cylinders 11. The exhaust gas discharged from the multiple cylinders 11 then flows through the exhaust passage 16. The internal combustion engine 10 is equipped with a supercharger 30. The supercharger 30 comprises a turbine 31 installed in the exhaust passage 16 and a compressor 32 installed in the intake passage 13. The turbine 31 is operated by the force of the exhaust gas flowing through the exhaust passage 16. The compressor 32 is located in the intake passage 13, upstream of the intercooler 21. The compressor 32 operates in sync with the turbine 31, thereby supercharging the air flowing through the intake passage 13. <Configuration of the exhaust gas recirculation system> The exhaust gas recirculation system 100 includes a high-pressure EGR device 40,