Cylinder-by-Cylinder Air-Fuel Ratio Controller with Time Correction
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Solution Overview
Problem
Existing cylinder-by-cylinder air-fuel ratio control systems for internal combustion engines face challenges in accurately and efficiently correcting air-fuel ratio detecting time deviations, leading to prolonged correction times and potential deterioration in exhaust emission and sensor malfunction detection.
Innovation Solution
A cylinder-by-cylinder air-fuel ratio controller that includes a first time-correction portion to maximize dispersion of detection values in one engine cycle and a second time-correction portion to adjust air-fuel ratio detecting time based on the correlation coefficient between estimated air-fuel ratio and correction value variations, allowing for rapid and accurate correction of detecting time deviations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the air-fuel ratio detecting time is retarded by a specified crank angle repeatedly to correct significant deviation, then the air-fuel ratio detecting time can be corrected, but it takes a long time period which may cause deterioration in exhaust emission and delayed malfunction detection
Solution Approach 1:
The system performs preliminary identification of the most appropriate air-fuel ratio detecting time by analyzing the relationship between estimated air-fuel ratio variations and corrected fuel amounts before actual correction is needed. This allows the system to pre-calculate and store correction values, so when significant deviation occurs, the correction can be applied immediately without repeated iterative adjustments.
Solution Approach 2:
The system continuously monitors the relationship between estimated air-fuel ratio variations and corrected fuel amounts to provide feedback on detecting time accuracy. By analyzing this feedback information, the system can determine whether the current detecting time is appropriate and make precise corrections without requiring multiple repeated adjustments.
2Measurement precision
If the air-fuel ratio detecting time is corrected by repeatedly computing correlation coefficients with incremental retardation, then the most appropriate detecting time can be learned, but the correction process takes excessively long when significant deviation exists
Solution Approach 1:
Instead of incrementally retarding the detecting time by fixed crank angle steps, the system changes the approach by directly calculating the optimal detecting time based on the correlation between estimated air-fuel ratio variations and corrected fuel amounts. This parameter-based calculation method allows for direct determination of the optimal time point without iterative stepping, significantly improving correction speed while maintaining accuracy.
3Device complexity
If incremental correction by fixed crank angle steps is used, then the correction process is simple, but it cannot achieve high accuracy when the most appropriate time significantly deviates from current time
Solution Approach 1:
The system introduces an intermediary analysis step that examines the relationship between estimated air-fuel ratio variations and corrected fuel amounts. This intermediary analysis acts as a bridge between the simple incremental correction approach and the need for high accuracy, allowing the system to determine the optimal detecting time through correlation analysis rather than simple fixed-step iteration.
Data Source
AI summary
When executing a Local-learning, an air-fuel ratio detecting time is corrected so that a dispersion of detection values of an air-fuel ratio sensor becomes a maximum value in one cycle of an engine. While executing a cylinder-by-cylinder air-fuel ratio control, a Global-learning is executed. In the Global-learning, the air-fuel ratio detecting time is corrected based on a relationship between a variation in estimated air fuel ratio of each cylinder and a variation in fuel quantity correction value of each cylinder. In the Global-learning, a computer computes a correlation coefficient between the variation in estimated air-fuel ratio and the variation in fuel quantity correction value of the cylinder for each case where the cylinder assumed to correspond to the estimated air fuel ratio is hypothetically varied in multiple ways. Then, the air-fuel ratio detecting time is corrected so that this correlation coefficient becomes a maximum value.