V8 Fuel Control Using Cylinder-Pair Oxygen Sensor Feedback
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Solution Overview
Problem
Cylinder firing intervals in cross-plane crankshaft V8 engines cause uneven residency times of exhaust pulses, leading to discrepancies in air-fuel ratio imbalance signals, which existing closed-loop fuel control systems struggle to accurately detect and correct.
Innovation Solution
Implementing four upstream oxygen sensors per cylinder bank and a controller with both decoupled and coupled fuel controllers to precisely adjust fuel mass based on individual and averaged lambda values, respectively, ensuring precise air-fuel ratio control and reduced emissions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a single oxygen sensor is used per cylinder bank to monitor air-fuel ratio, then the system complexity is reduced, but the measurement precision of air-fuel ratio imbalance deteriorates due to varying exhaust pulse residency times
Solution Approach 1:
The patent divides the monitoring function by assigning a dedicated oxygen sensor to each cylinder pair (1-2, 3-4, 5-6, 7-8), allowing independent measurement of air-fuel ratios for each pair. This segmentation eliminates the measurement precision deterioration caused by varying exhaust pulse residency times that would occur with a single shared sensor, as each sensor measures only its own cylinder pair's exhaust without interference from other cylinders.
Solution Approach 2:
The patent implements a feedback mechanism where the controller continuously monitors lambda values from each oxygen sensor and adjusts fuel injection quantities for individual cylinder pairs accordingly. The controller calculates air-fuel ratio imbalances by comparing lambda values between different cylinder pairs and provides corrective feedback by modifying fuel delivery to maintain balanced operation across all cylinders.
2Measurement precision
If multiple oxygen sensors are deployed for each cylinder pair, then the air-fuel ratio control precision is improved, but the device complexity and cost increase
Solution Approach 1:
The patent segments the cylinder bank into pairs (1-2, 3-4, 5-6, 7-8) and assigns one oxygen sensor to each pair, rather than using a single sensor for the entire bank or multiple sensors for each individual cylinder. This segmentation approach achieves the necessary measurement precision for detecting inter-cylinder imbalances while avoiding the excessive complexity that would result from more extensive sensor deployment.
Solution Approach 2:
The patent merges the monitoring of two cylinders into a single sensor assignment per cylinder pair. By combining cylinders 1 and 2 under one sensor, cylinders 3 and 4 under another, and so on, the system achieves sufficient measurement precision to detect imbalances between pairs while reducing the total sensor count compared to individual cylinder monitoring.
3Productivity
If traditional single-sensor per bank control is used, then the system is simpler to implement, but the convergence speed to requested air-fuel ratio is slower and emissions are higher
Solution Approach 1:
The patent implements a feedback control system where the controller continuously receives lambda values from oxygen sensors, compares them against target values, and adjusts fuel injection quantities in real-time. This closed-loop feedback mechanism enables faster convergence to the requested air-fuel ratio by immediately correcting deviations, thereby reducing emissions compared to open-loop or less sophisticated control systems.
Solution Approach 2:
The patent employs dynamic fuel control by continuously adjusting fuel injection quantities based on real-time oxygen sensor feedback. The controller dynamically modifies fuel delivery to each cylinder pair according to measured air-fuel conditions, enabling rapid adaptation to changing operating conditions and faster convergence to target air-fuel ratios compared to static or pre-programmed fuel maps.
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
Enhances air-fuel ratio control precision and reduces engine emissions by allowing faster convergence to the requested ratio, particularly during cold starts, while maintaining stability and efficiency.
Implementation Method 1
The measured air-fuel ratio may be inferred via an oxygen sensor that senses exhaust gases
Data Source
AI summary
Systems and methods for controlling fuel that is supplied to cylinders of an internal combustion engine are described. In one example, oxygen sensors are placed in an exhaust system of an engine such that each oxygen sensor may detect exhaust gas from a pair of engine cylinders. The oxygen sensors may then provide feedback to coupled and decoupled fuel controllers.