Engine Air-Fuel Ratio Control for Catalyst Oxygen Storage
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Solution Overview
Problem
Existing control systems for internal combustion engines face challenges in suitably changing the speed of updating the learning value when alternately switching between rich and lean air-fuel ratios, leading to potential convergence issues.
Innovation Solution
A control system that adjusts the air-fuel ratio between rich and lean settings based on oxygen storage in the exhaust purification catalyst, using feedback from downstream air-fuel ratio sensors to update the learning value, with specific adjustment methods to manage the speed of this update.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the target air-fuel ratio is alternately switched between rich and lean air-fuel ratios, then the oxygen storage in the exhaust purification catalyst is maintained, but the learning value cannot be updated using conventional methods leading to convergence issues
Solution Approach 1:
The patent applies dynamics by making the learning value update mechanism adaptive rather than static. The control device dynamically adjusts the update frequency and incorporation ratio based on operating conditions (engine speed, load, compression ratio), allowing the system to handle both alternating air-fuel ratio control and learning value convergence requirements effectively
Solution Approach 2:
The patent changes parameters by introducing conditional logic that modifies the learning value update behavior based on engine operating parameters. When alternating between rich and lean air-fuel ratios, the system adjusts the update frequency and incorporation ratio according to engine speed, load, and compression ratio, enabling effective learning value convergence under varying operational modes
2Productivity
If the speed of updating the learning value is increased by shortening time interval and increasing incorporation ratio, then the learning value converges quickly, but the system complexity increases
Solution Approach 1:
The patent uses dynamics to adjust the learning value update speed based on real-time operating conditions. Rather than using a fixed high update rate, the system dynamically modifies the time interval and incorporation ratio according to engine speed, load, and compression ratio, achieving fast convergence when needed while maintaining simplicity under normal conditions
Solution Approach 2:
The patent changes control parameters conditionally - the time interval for incorporating learning values and the incorporation ratio are adjusted based on engine operating parameters. This allows the system to achieve fast convergence speed when required (high productivity) while maintaining simpler control logic under standard operating conditions, thus avoiding unnecessary system complexity
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
Enables effective and controlled updating of the learning value, improving the engine's ability to manage air-fuel ratios and reduce unburned gases and NOx emissions by maintaining optimal oxygen storage in the catalyst.
Implementation Method 1
when the air-fuel ratio detected by the downstream side air-fuel ratio sensor becomes a rich judged air-fuel ratio (air-fuel ratio slightly richer than stoichiometric air-fuel ratio) or less, the target air-fuel ratio is set to an air-fuel ratio which is leaner than the stoichiometric air-fuel ratio
Data Source
Figure 1
Figure 2A~2B
Figure 3~4
AI summary
An internal combustion engine comprises an exhaust purification catalyst 20 and a downstream side air-fuel ratio sensor which is arranged at the downstream side of the exhaust purification catalyst. The control system performs feedback control so that the air-fuel ratio of the exhaust gas becomes the target air-fuel ratio, and performs learning control to correct the control center air-fuel ratio based on the output air-fuel ratio of the downstream side sensor. The target air-fuel ratio is switched to the lean air-fuel ratio when the output air-fuel ratio of the downstream side sensor becomes the rich judged air-fuel ratio and is switched to the rich air-fuel ratio when the output air-fuel ratio becomes the lean judged air-fuel ratio. When the learning promoting condition stands, the lean degree of the average target air-fuel ratio while the target air-fuel ratio is set to the lean air-fuel ratio and the rich degree of the average target air-fuel ratio while the target air-fuel ratio is set to the rich air-fuel ratio are increased.