Cylinder Air Charge Estimation for Variable Displacement Engines
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
In engines with rolling variable displacement engine (VDE) systems, the order of cylinder deactivation and reactivation leads to significant cylinder-to-cylinder air flow variability, causing imbalances in air-fuel ratios and affecting engine operation and emissions due to differences in intake and exhaust valve operations.
Innovation Solution
An air charge estimation method that adjusts based on the induction pattern history, using two different calibrations to account for the presence or absence of valve overlap, ensuring accurate volumetric efficiency calibration and reducing computation intensity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If rolling variable displacement engine (VDE) systems deactivate and reactivate cylinders in different orders, then fuel economy is improved, but cylinder-to-cylinder air flow variability increases causing air-fuel ratio imbalances
Solution Approach 1:
The system performs preliminary classification of cylinders into two groups based on their induction pattern history before calculating air charge estimates. This preliminary action allows the system to apply different volumetric efficiency calibrations to each group, thereby maintaining accurate air-fuel ratio control while enabling rolling VDE operation that improves fuel economy.
Solution Approach 2:
The patent applies different volumetric efficiency calibrations to different cylinders based on their individual induction patterns. Instead of using a uniform calibration for all cylinders, the system tailors the calibration to each cylinder's specific operational history, thereby maintaining precise air-fuel ratio control across all cylinders despite varying deactivation and reactivation orders.
2Measurement precision
If different volumetric efficiency calibrations are applied to cylinders based on induction pattern history, then air charge estimation accuracy is improved, but computation intensity increases
Solution Approach 1:
The system segments cylinders into two distinct groups based on their induction pattern history (whether the cylinder was inducted or skipped in the previous cycle). This segmentation allows the use of two different but simpler volumetric efficiency calibrations instead of requiring a complex single calibration that would account for all possible induction patterns, thereby reducing overall computation intensity while maintaining accuracy.
Data Source
AI summary
Systems and methods are provided for increasing the accuracy of air charge estimation for a cylinder that is selectively deactivatable. A controller may deactivate the cylinder in accordance with a firing pattern selected based on torque demand. An air charge estimate of the firing cylinder is then adjusted based on whether the cylinder was fired or skipped on a previous engine cycle when operating according to the selected firing pattern.