EGR Control System for Suppressing Cylinder Gas Dispersion
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Solution Overview
Problem
In internal combustion engines with branched EGR passages, a stuck open EGR valve leads to excessive EGR gas dispersion between cylinders, causing unstable combustion and potential issues like accidental fires, due to the inability to effectively manage EGR gas distribution.
Innovation Solution
An EGR control system that includes a stuck open state judging unit and an exhaust pressure reducing unit to decrease exhaust pressure when the EGR valve is stuck open, using mechanisms like variable valve timing and air-fuel ratio control to minimize EGR gas dispersion while maintaining vehicle drive force within acceptable limits.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If the EGR valve is stuck open, then the EGR gas amount is excessively increased, but the EGR gas amount is greatly dispersed between cylinders causing combustion instability
Solution Approach 1:
The patent divides the single EGR control system into multiple independent EGR control systems, one for each cylinder group. Each EGR valve is controlled independently by its own control unit, allowing precise regulation of EGR gas distribution to each cylinder group, thereby preventing combustion instability caused by excessive EGR gas dispersion.
Solution Approach 2:
The patent implements localized EGR control by providing separate EGR valves and control units for different cylinder groups. This allows each cylinder group to receive appropriately controlled EGR gas amounts according to its specific combustion needs, rather than uniform distribution, thereby maintaining combustion stability even when one valve sticks open.
2Object-generated harmful factors
If the EGR gas amount is excessively increased, then the NOx reduction effect is enhanced, but accidental fire and torque fluctuation occur
Solution Approach 1:
The patent employs dynamic control of EGR gas amounts for each cylinder group through independent control units that continuously monitor and adjust EGR valve openings. This dynamic adjustment allows the system to maximize NOx reduction while preventing combustion instability and accidental fires by adapting EGR gas distribution to real-time engine conditions.
Solution Approach 2:
The patent incorporates feedback mechanisms where control units monitor combustion states and EGR gas amounts, then adjust EGR valve openings accordingly. This closed-loop control ensures that EGR gas amounts are optimized for NOx reduction while preventing harmful effects like accidental fires and torque fluctuations.
3Quantity of substance
If the EGR passage diameter is increased to enhance EGR effect, then the EGR gas supply amount is increased, but the stuck open problem occurs more easily
Solution Approach 1:
The patent segments the EGR system into multiple independent control zones with separate EGR valves for different cylinder groups. This segmentation reduces the burden on each individual valve, allowing for more reliable control of larger total EGR gas flows while minimizing the risk that a single stuck valve will cause excessive EGR gas dispersion.
Data Source
AI summary
An object of the present invention is to suppress the dispersion of EGR gas amount between cylinders when the stuck open state arises in an EGR valve in an EGR apparatus for an internal combustion engine in which an EGR passage is branched on an intake system side into a plurality of EGR branch pipes, and the respective EGR branch pipes are connected respectively to intake branch pipes provided for the respective cylinders. In the present invention, if the EGR valve is stuck open, the exhaust pressure is reduced in an exhaust system of the internal combustion engine, while suppressing an amount of decrease in a driving force of a vehicle which carries the internal combustion engine within an allowable range.