Cylinder Imbalance Detection Using Multi-Sensor Torque Control
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Solution Overview
Problem
Existing methods for detecting cylinder-to-cylinder air-fuel ratio (AFR) imbalances in internal combustion engines are unreliable due to insufficient exhaust gas mixing and sensor warm-up issues, especially during cold-start conditions, leading to torque errors and reduced engine performance.
Innovation Solution
A method that combines exhaust air-fuel ratio estimates from an exhaust gas sensor, exhaust manifold pressure from a pressure sensor, and individual cylinder torque from a crankshaft torque sensor, with confidence factors adjusted based on operating conditions to improve the reliability of imbalance detection across a broader range of engine operating conditions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If exhaust gas sensor is used to detect AFR imbalance, then AFR detection is possible, but detection reliability deteriorates during cold-start and insufficient mixing conditions
Solution Approach 1:
The patent combines multiple detection approaches (exhaust gas sensor, exhaust manifold pressure sensor, and crankshaft torque sensor) into a unified detection system. By merging these different measurement methods, the system achieves reliable AFR imbalance detection across all operating conditions, including cold-start and insufficient mixing conditions where individual sensors would fail.
Solution Approach 2:
The control system is designed to perform multiple functions: it can detect AFR imbalance using exhaust gas sensors during normal operation, switch to exhaust manifold pressure-based detection during cold-start, and use crankshaft torque analysis for verification. This multi-functional approach ensures universal detection capability across diverse operating conditions.
2Measurement precision
If exhaust manifold pressure sensor is used to detect AFR imbalance, then detection is possible, but reliability deteriorates with increased distance from cylinder
Solution Approach 1:
The patent combines exhaust manifold pressure sensor detection with crankshaft torque sensor detection. By merging these two measurement methods, the system compensates for the distance-related reliability issues of the pressure sensor alone, as the torque sensor provides independent verification that is not affected by sensor positioning.
3Device complexity
If single detection method is used, then system complexity is low, but detection reliability varies based on operating conditions
Solution Approach 1:
The detection system dynamically selects and weights different detection methods based on current operating conditions. During cold-start, the system relies more on exhaust manifold pressure and torque data; during normal operation, it incorporates exhaust gas sensor data. This dynamic adaptation maintains high reliability across varying conditions without requiring a permanently complex system architecture.
Solution Approach 2:
The system changes the weighting parameters of different detection methods based on operating conditions. The confidence factor assigned to each detection method varies dynamically - for example, exhaust gas sensor data is weighted higher during warm operating conditions while torque-based detection is weighted higher during cold-start. This parameter adjustment allows reliable detection without permanent system complexity.
Data Source
AI summary
Methods and systems are provided for detecting air-fuel ratio imbalances across all engine cylinders. In one example, a method (or system) may include indicating cylinder imbalance based on each of the exhaust air-fuel ratio, exhaust manifold pressure, and cylinder torque weighted by a confidence factor, where in the confidence factor is determined based on operating conditions.