Engine Fuel Purge Control for Air-Fuel Ratio Stability
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Solution Overview
Problem
Conventional control apparatuses for internal combustion engines face challenges in maintaining a stable air-fuel ratio after the evaporated fuel gas purge is stopped, leading to excessive deviations from the stoichiometric ratio, which results in increased NOx emissions and worsened emissions control.
Innovation Solution
The control apparatus adjusts the feedback correction coefficient and purge correction coefficient by learning the evaporated fuel gas concentration and estimating the purge flow, allowing for precise correction of the fuel injection amount to maintain the air-fuel ratio close to the stoichiometric ratio even after the purge control valve is closed, thereby reducing NOx emissions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If the feedback correction coefficient is reset to base value when the purge control valve is completely closed, then the control complexity is reduced, but the air-fuel ratio deviates excessively from the stoichiometric ratio after purge stops
Solution Approach 1:
The control apparatus performs preliminary action by resetting the feedback correction coefficient to the base value at the purge control valve closing instruction timing (before the evaporated fuel gas actually stops entering the combustion chamber), rather than waiting until the purge is completely stopped. This anticipatory reset prevents excessive air-fuel ratio deviation while maintaining straightforward control logic.
2Stability of the object's composition
If the feedback correction coefficient is not reset when the purge control valve is closed, then the air-fuel ratio remains stable, but the NOx emissions increase due to excessive lean condition
Solution Approach 1:
The control apparatus uses feedback mechanism by continuously monitoring the air-fuel ratio sensor output and adjusting the feedback correction coefficient accordingly. The coefficient is reset to base value at the purge closing instruction timing, and the system responds to air-fuel ratio deviations through feedback control, preventing excessive lean conditions and reducing NOx emissions while maintaining stability.
3Measurement precision
If the purge correction coefficient is used to compensate for air-fuel ratio deviation during purge, then the air-fuel ratio control accuracy is improved, but the device complexity increases due to additional correction mechanisms
Solution Approach 1:
The control apparatus merges the feedback correction coefficient and purge correction coefficient into a unified control mechanism. Both correction coefficients work together within the same control loop, with the feedback correction coefficient being reset at the purge closing instruction timing and the purge correction coefficient compensating for air-fuel ratio deviations. This integrated approach improves control accuracy without requiring separate independent control systems.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach effectively minimizes the deviation of the air-fuel ratio from the target ratio after the purge control valve closing, leading to improved emissions control and reduced NOx emissions.
Implementation Method 1
The evaporated fuel generated in the fuel tank is introduced into the canister through the purge passage, and is adsorbed in the canister tentatively.
Data Source
Figure 1
Figure 2
Figure 3(A)~3(E)
AI summary
An evaporated fuel gas concentration learning section A8 renews an evaporated fuel gas concentration learning value based on a feedback correction amount FAF. An estimated purge rate calculating section A9 estimates, a flow of an evaporated fuel gas introduced into a combustion chamber based on a flow KP of an evaporated fuel gas passing throuth a purge control valve in consideration of a transportation delay time duration and a behavior of the evaporated fuel gas. An instructed injection amount determining section A10 calculates a purge correction amount based on the evaporated fuel gas concentration learning value and the estimated purge flow. An evaporated fuel gas purge stop timing adjusting section A11, at a purge control valve closing instruction timing, corrects the feedback correction amount to a base value and corrects the evaporated fuel gas concentration learning value so as to add, to the purge correction amount, an amount corresponding to an correction amount to correct the base injection amount provided by the feedback correction amount at a timing immediately before the feedback correction amount is corrected to the base value.