Air-Fuel Ratio Imbalance Detection Using Load Factor Normalization
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Solution Overview
Problem
Existing air-fuel ratio imbalance detecting devices for internal combustion engines fail to accurately detect imbalances due to not incorporating load factor differences, leading to potential misclassification of engine states.
Innovation Solution
The device normalizes air-fuel ratio variations using a constant associated with rotation speed and load factor, allowing for more precise detection of imbalances by averaging multiple normalized minimum values to reduce false positives from other factors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a constant based only on intake air amount is used for normalization, then the detection method is simple, but the detection accuracy deteriorates due to load factor differences
Solution Approach 1:
The patent changes the normalization parameters from using only intake air amount to using both intake air amount and load factor. This allows the normalized value to account for different operating conditions, thereby improving detection accuracy without significantly increasing system complexity.
Solution Approach 2:
The patent introduces dynamic adjustment of the normalized value based on real-time load factor changes. By continuously updating the normalized variation per unit time according to current load conditions, the system maintains high detection accuracy across varying operating states.
2Productivity
If the normalized value is calculated without considering load factor, then the calculation is fast and simple, but false detections increase
Solution Approach 1:
The patent modifies the normalization parameters to include load factor alongside intake air amount. This change ensures that variations in operating conditions are properly accounted for, reducing false detections while maintaining efficient calculation through straightforward parameter updates.
3Ease of operation
If a fixed threshold is used for imbalance detection, then the detection criterion is clear and simple, but accurate detection under varying load conditions deteriorates
Solution Approach 1:
The patent implements a dynamic threshold determination method where the threshold is adjusted based on the normalized value that incorporates current load factor. This allows the detection criterion to adapt to varying operating conditions, maintaining both clarity and accuracy across different engine states.
Data Source
AI summary
An air-fuel ratio imbalance detecting device for an internal combustion engine, which detects a rich imbalance in air-fuel ratio among a plurality of cylinders on the basis of a variation per unit time in air-fuel ratio that is detected by an air-fuel ratio sensor provided in an exhaust passage of the internal combustion engine, includes an electronic control unit that normalizes the variation per unit time in air-fuel ratio with a constant associated with a rotation speed and load factor of the internal combustion engine and that, when the normalized value is smaller than a predetermined threshold, determines that a rich imbalance in air-fuel ratio has been detected among the cylinders.