Engine Air Charge Estimation via Cylinder Firing Pattern Adjustment
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Solution Overview
Problem
In variable displacement engines, accurately estimating cylinder air charge is challenging due to the numerous firing patterns, leading to over-complexity and inaccurate estimates, which degrade engine efficiency and affect emission control.
Innovation Solution
The method involves adjusting air charge estimates for a given cylinder based on the combustion or non-combustion of a second cylinder, 180 degrees out of phase, by specific amounts depending on the firing patterns in previous and current cycles, to improve estimation accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If multiple look-up tables are generated for different firing patterns, then air charge estimation accuracy is improved, but device complexity increases significantly
Solution Approach 1:
The patent creates a single universal look-up table that can be used across all firing patterns by adjusting the air charge estimate based on the firing status of other cylinders. Instead of generating separate look-up tables for each firing pattern (2-position VDE, selective non-fueling, etc.), one table is generated and then adaptively adjusted, making the system multi-functional across different operating modes.
Solution Approach 2:
The patent changes the parameter being estimated from raw air charge to adjusted air charge estimate. By modifying the estimation parameter to account for the firing patterns of other cylinders, the system achieves accuracy across multiple firing patterns without needing multiple separate look-up tables, thus reducing complexity while maintaining precision.
2Device complexity
If a single look-up table is used for all firing patterns, then device complexity is reduced, but air charge estimation accuracy deteriorates
Solution Approach 1:
The system uses feedback from the firing status of other cylinders to adjust the air charge estimate. The controller monitors which cylinders are firing or not firing and uses this information to modify the estimate from the single look-up table, ensuring accuracy is maintained across different firing patterns without requiring multiple tables.
Solution Approach 2:
The patent performs preliminary generation of a single comprehensive look-up table that covers all possible firing patterns, then applies corrective adjustments based on actual operating conditions. This preliminary action of creating one universal table simplifies the system architecture while the subsequent adjustment ensures accuracy.
3Device complexity
If inaccurate air charge estimates are used, then fuel injection and emission control may be simplified, but engine efficiency and emission performance deteriorate
Solution Approach 1:
The system uses information already available in the control system (firing status of cylinders) to self-adjust the air charge estimate. No additional sensors or complex external systems are needed - the existing control data is repurposed to improve estimation accuracy, maintaining control simplicity while enhancing engine efficiency.
Data Source
AI summary
Systems and methods are provided. In one example, a method for an engine comprises adjusting an air charge estimate for a first cylinder based on a firing pattern of a second cylinder. In this way, cylinder air charge estimates may be improved in real-time for an arbitrary cylinder firing pattern, thereby improving engine efficiency.