Engine Air-Fuel Imbalance Detection Using Oxygen Sensor Coefficients
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Solution Overview
Problem
Internal combustion engines with multiple cylinders face challenges in determining and compensating for individual cylinder air-fuel ratio imbalances, as existing methods struggle to accurately assess imbalances using a single oxygen sensor exposed to exhaust gases from all cylinders, leading to reduced catalyst efficiency and increased emissions.
Innovation Solution
An engine operating method that adjusts fuel supply based on a cylinder lambda deviation, using a relationship between a fuel mass multiplier and a coefficient derived from oxygen sensor output to a step change in fuel mass, allowing for the determination and compensation of air-fuel ratio imbalances without increasing system hardware costs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a single oxygen sensor is used to monitor exhaust gases from all cylinders, then system cost is reduced, but the ability to accurately determine individual cylinder air-fuel ratio imbalances deteriorates
Solution Approach 1:
The patent applies segmentation by mathematically separating the combined oxygen sensor signal into individual cylinder contributions. The controller divides the exhaust gas analysis by attributing signal components to specific cylinders based on their firing sequences and temporal patterns, enabling individual cylinder air-fuel ratio determination without physical sensor segmentation.
Solution Approach 2:
The patent uses the oxygen sensor output signal as an intermediary to indirectly determine individual cylinder air-fuel ratios. By processing the combined exhaust gas signal through mathematical relationships and temporal analysis, the system extracts cylinder-specific information without requiring direct measurement from each cylinder.
2Device complexity
If traditional oxygen sensor analysis methods are used, then system complexity is low, but the ability to compensate for cylinder imbalances deteriorates
Solution Approach 1:
The patent implements feedback by continuously monitoring the oxygen sensor output and adjusting fuel injection quantities for individual cylinders based on detected air-fuel ratio deviations. The controller compares measured values against target values and applies corrective fuel adjustments to maintain optimal air-fuel ratios despite manufacturing variations and wear.
Solution Approach 2:
The patent changes the parameter being analyzed from raw oxygen sensor voltage to derived coefficients and lambda deviations. By transforming the sensor output through mathematical relationships and identifying specific signal characteristics, the system extracts meaningful cylinder-specific information that enables reliable compensation.
3Measurement precision
If fuel injection is adjusted based on noisy oxygen sensor outputs, then air-fuel ratio control precision may improve, but system reliability deteriorates due to noise
Solution Approach 1:
The patent applies preliminary action by pre-processing the oxygen sensor signal through mathematical transformations and coefficient extraction before using it for control decisions. The system establishes baseline relationships between fuel mass multipliers and sensor output coefficients, then uses these pre-established models to filter noise and extract reliable cylinder-specific information.
Solution Approach 2:
The patent transforms the noisy oxygen sensor output into more reliable parameters including time constants, coefficients, and lambda deviations. By changing from direct voltage analysis to derived mathematical parameters, the system reduces the impact of noise while maintaining sensitivity to actual air-fuel ratio conditions.
Data Source
AI summary
Systems and methods for operating an engine that includes an oxygen sensor and one or more fuel injectors for each engine cylinder are described. In one example, lines describing a relationship between a fuel mass multiplier and a coefficient of a function describing output of an oxygen sensor to a step change in fuel mass are a basis for determining air-fuel imbalance of engine cylinders.