Engine Throttle and Cam Phaser Coordination for Dilution Control
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Solution Overview
Problem
Internal combustion engines with variable camshaft phasing face challenges in maintaining optimal fuel mixture dilution during transient speed and load changes, leading to unstable combustion, reduced fuel economy, and increased NOx emissions due to mismatched phaser response rates.
Innovation Solution
A method involving an Engine Control Module (ECM) that dynamically adjusts throttle position and cam phaser positions to maintain desired dilution levels by predicting engine conditions and calculating optimal airflow and phaser positions at sequential transient positions, allowing phasers to move as fast as possible while coordinating airflow to achieve optimal dilution.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If the cam phaser response rate is increased to quickly adjust valve timing during transient operation, then the ability to maintain optimal dilution improves, but excessive dilution occurs when engine load is increasing, causing unstable combustion
Solution Approach 1:
The ECM predicts future engine load conditions and proactively adjusts the cam phaser position in advance to anticipate the required dilution level. This predictive approach allows the phaser to be positioned optimally before the transient condition fully develops, preventing both excessive and insufficient dilution during rapid load changes.
Solution Approach 2:
The system dynamically adjusts the cam phaser response characteristics based on real-time engine operating conditions. The ECM modulates the phaser position commands to deliver the desired residual dilution fraction dynamically, coordinating phaser movement with throttle response to maintain optimal dilution across varying transient scenarios.
2Reliability
If the cam phaser is calibrated conservatively to avoid excessive dilution and unstable combustion, then combustion stability improves, but fuel economy deteriorates and NOx emissions increase
Solution Approach 1:
By predicting future engine load conditions and proactively adjusting the cam phaser position in advance, the system maintains optimal dilution levels during transient operation without requiring conservative calibration. This eliminates the trade-off between combustion stability and fuel economy that plagues traditional approaches.
Solution Approach 2:
The ECM continuously monitors actual engine performance and phaser position, using this feedback to dynamically adjust control commands. This closed-loop control ensures optimal dilution is maintained while adapting to varying operating conditions, improving both combustion stability and fuel economy compared to open-loop conservative calibration.
3Manufacturing precision
If the throttle is dynamically adjusted to coordinate airflow with phaser movement during transients, then optimal dilution is maintained, but control complexity increases
Solution Approach 1:
The control of the cam phaser and throttle is merged into a coordinated system managed by the ECM. The ECM simultaneously adjusts both components to achieve the desired dilution level, with the throttle dynamically adjusted to properly coordinate airflow with phaser movement. This integrated approach maintains precise dilution control while using a single control module to manage both actuators.
Data Source
AI summary
A method for coordinating engine throttle position with camshaft phaser motion during transient engine operation such that desired internal residual dilution is maintained. A dilution model for residual mass fraction and a table of desired dilution values are embedded in the engine control algorithm. The dilution model is applied to calculate the desired throttle and camshaft phaser positions for the next intake event. In a first method, if the throttle is capable of changing the airflow into the engine cylinders faster than the camshaft phasers can respond, the throttle is modulated to maintain desired dilution levels while the phasers are allowed to move as fast as they can. In a second method, if the phaser response faster than the engine intake port airflow response to a throttle position change, the throttle is allowed to move as fast as it can while phaser motion is modulated to maintain desired dilution levels.