Individual Cylinder Air-Fuel Ratio Monitoring Enablement
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Solution Overview
Problem
Multi-cylinder internal combustion engines face challenges in reliably detecting air-fuel ratio imbalances among cylinders, particularly due to transient changes in torque demand and purge errors, which limits the conditions under which monitoring can be performed, and existing strategies require multiple engine cycles to complete diagnostics.
Innovation Solution
Implementing an individual cylinder-based enablement grid that activates air-fuel ratio monitoring only for subsets of cylinders determined to have reliable detectability at specific engine operating points, using a lookup table to select cylinders with predetermined criteria met, and repeating measurements until a predetermined number of air-fuel ratio determinations are obtained for each cylinder.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a single sensor is used for multiple cylinders, then device complexity is reduced, but measurement precision for individual cylinder AFR detection deteriorates
Solution Approach 1:
The patent segments the monitoring task by dividing cylinders into subsets based on their detectability characteristics. Instead of treating all cylinders equally, the system identifies and monitors subsets of cylinders that can be reliably detected under current operating conditions, allowing precise individual cylinder monitoring while using a single shared sensor.
Solution Approach 2:
The patent applies local quality by enabling monitoring only for specific subsets of cylinders that meet predetermined detectability criteria at given operating points. Rather than attempting uniform monitoring across all cylinders, the system selectively monitors only those cylinders where reliable detection is possible, improving measurement precision for monitored cylinders while maintaining system simplicity.
2Productivity
If monitoring is performed under all engine operating conditions, then productivity is improved, but measurement precision deteriorates due to transient changes and purge errors
Solution Approach 1:
The patent implements dynamic monitoring enablement where the set of monitorable cylinders changes based on current engine operating conditions. The controller dynamically determines which cylinders can be reliably monitored at each operating point using a speed-load enablement grid, allowing the system to adapt to changing conditions and maintain measurement precision while maximizing productivity across diverse operating scenarios.
Solution Approach 2:
The patent changes the operational parameters by establishing predetermined criteria for cylinder detectability based on engine speed and load regions. By defining specific operating conditions under which cylinders can be reliably monitored, the system ensures measurement precision is maintained while still achieving high diagnostic completion rates through cumulative monitoring across multiple operating points.
3Measurement precision
If the worst cylinder of the group determines the enablement grid, then measurement precision is maintained, but productivity decreases due to extended monitoring cycles
Solution Approach 1:
The patent segments the cylinder group into multiple subsets, each with its own detectability characteristics. Instead of having the worst cylinder constrain the entire group, the system identifies separate subsets of cylinders that can be monitored under different operating conditions. This allows each subset to be monitored independently, improving overall diagnostic completion rate while maintaining precision for each monitored subset.
Solution Approach 2:
The patent applies partial action by monitoring only the subset of cylinders that can be reliably detected under current operating conditions, rather than requiring all cylinders to meet the same stringent criteria. This partial monitoring approach allows the diagnostic to progress and complete faster by accumulating measurements from available subsets across different operating points, while still achieving sufficient precision for the monitored cylinders.
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
This approach enhances the diagnostic completion rate and expands air-fuel ratio imbalance monitoring beyond conditions limited by the weakest cylinder, reducing unnecessary interventions and improving fuel economy by enabling monitoring under a wider range of engine conditions.
Implementation Method 1
monitoring of exhaust gas oxygen by one or more exhaust gas oxygen (EGO) sensors
Data Source
AI summary
A vehicle includes an internal combustion engine having a plurality of cylinders, a sensor configured to generate a sensor signal correlated with an air-fuel ratio of first and second cylinders of the plurality of cylinders, and a controller in communication with the sensor and programmed to monitor the air-fuel ratio of the first cylinder in response to an indication that air-fuel ratio measurements of the first cylinder satisfy predetermined criteria for current engine operating conditions while air-fuel ratio measurements of the second cylinder do not satisfy the predetermined criteria for the current engine operating conditions.