Engine Controller Air-Fuel Ratio Sub-Feedback Control
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Solution Overview
Problem
The existing engine control systems face challenges in precisely controlling the oxygen supply to oxidation catalysts, which is necessary for removing ammonia generated by three-way catalysts, as the amount of ammonia varies with engine running conditions.
Innovation Solution
An engine controller is configured with air-fuel ratio sensors upstream and downstream of the three-way and oxidation catalysts, performing sub-feedback control to switch between rich and lean air-fuel ratios, and variably setting the lean determination value based on ammonia generation amounts to optimize oxygen storage in the oxidation catalyst.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the amount of oxygen in the oxidation catalyst is increased to remove ammonia, then ammonia removal efficiency is improved, but the control precision becomes difficult when ammonia generation amount varies
Solution Approach 1:
The engine controller uses feedback from the air-fuel ratio sensor to continuously monitor and adjust the air-fuel ratio. When the detected air-fuel ratio deviates from the target value, the controller automatically adjusts fuel injection or air intake to restore the target ratio, ensuring precise control of oxygen availability for ammonia removal despite varying engine conditions
Solution Approach 2:
The system dynamically adjusts the air-fuel ratio based on real-time engine operating conditions and ammonia generation rates. The controller varies the air-fuel ratio within a range including the stoichiometric ratio, allowing flexible adaptation to changing ammonia amounts while maintaining optimal oxygen supply for the oxidation catalyst
2Productivity
If the air-fuel ratio is switched between rich and lean to control oxygen supply, then oxygen storage in oxidation catalyst is optimized, but control complexity increases
Solution Approach 1:
The engine controller periodically switches the air-fuel ratio between rich and lean conditions in a cyclic manner. This periodic switching allows the oxidation catalyst to alternately store and release oxygen, optimizing ammonia removal efficiency while using a simple, repeatable control pattern that does not significantly increase system complexity
Solution Approach 2:
The system changes the air-fuel ratio parameter between different operating modes (rich and lean). By varying this single critical parameter, the controller optimizes oxygen supply to the oxidation catalyst without requiring complex multi-parameter control systems, maintaining relatively simple control architecture
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 enhances the efficiency of ammonia removal by adjusting oxygen storage in the oxidation catalyst according to varying ammonia generation rates, ensuring effective ammonia removal regardless of engine conditions.
Implementation Method 1
The oxidation catalyst of such an engine removes ammonia generated by the three-way catalyst by oxidizing the ammonia using oxygen supplied from the injector
Implementation Method 2
The three-way catalyst oxidizes and purifies hydrocarbon (HC) and carbon monoxide (CO) in exhaust gas
Implementation Method 3
the three-way catalyst reduces nitrogen oxide (NOx) in exhaust gas to purify the exhaust gas
Data Source
AI summary
An engine controller performs air-fuel ratio sub-feedback control in which a target air-fuel ratio is switched from a rich air-fuel ratio to a lean air-fuel ratio when a rear air-fuel ratio detected by an air-fuel ratio sensor becomes less than or equal to a rich determination value, and the target air-fuel ratio is switched from the lean air-fuel ratio to the rich air-fuel ratio when the rear air-fuel ratio becomes greater than or equal to a lean determination value. To perform the sub-feedback control, the controller variably sets the lean determination value to a value indicating a leaner air-fuel ratio when an amount of overshoot of the rear air-fuel ratio to a richer value than a stoichiometric air-fuel ratio after switching the target air-fuel ratio from the rich air-fuel ratio to the lean air-fuel ratio is relatively large than when the amount of overshoot is relatively small.