Fresh Air Estimation Using Valve Timing Correction
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Solution Overview
Problem
Existing methods for estimating the quantity of fresh air admitted into a combustion chamber of an engine cycle are inaccurate, especially when the engine operates at temperatures different from its nominal temperature, leading to increased errors, particularly when starting the engine cold.
Innovation Solution
A method that corrects the opening and closing angles of the valves based on estimated timing clearances between the valves and their rocker arms or camshaft, using a physical quantity representative of the engine temperature and time since start-up, allowing for precise estimation of fresh air quantity without measuring pressure or temperature inside the combustion chamber.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If the engine operates at temperatures different from nominal temperature, then the engine can start cold or operate under varying thermal conditions, but the estimation error of fresh air quantity increases
Solution Approach 1:
The patent applies parameter changes by dynamically adjusting the valve timing parameters (opening and closing angles) based on engine temperature and time since start-up. The ECU modifies these parameters to compensate for thermal expansion effects on valve clearance, thereby maintaining estimation accuracy across varying temperature conditions without requiring additional sensors.
Solution Approach 2:
The patent implements preliminary action by pre-calculating and storing correction values for valve timing parameters at different temperature conditions and time intervals. During cold start or temperature transitions, the ECU retrieves and applies these pre-determined corrections to the valve timing, eliminating the need for real-time complex calculations and ensuring immediate accuracy improvement.
2Device complexity
If valve timing clearances are not corrected for temperature effects, then the model calibration remains simple, but the opening and closing angles become inaccurate at non-nominal temperatures
Solution Approach 1:
The patent modifies the valve timing parameters (opening and closing angles) by applying temperature and time-based corrections. The ECU adjusts these parameters dynamically according to engine temperature and time since start-up, compensating for thermal expansion effects on valve clearance without requiring complex mechanical adjustments or additional sensors.
Solution Approach 2:
The patent replaces complex mechanical valve timing adjustment mechanisms with an electronic control system. Instead of physically adjusting valve clearances through mechanical means, the ECU calculates corrected timing parameters based on temperature and time data, substituting mechanical complexity with computational simplicity while maintaining high precision.
3Measurement precision
If pressure and temperature sensors are installed inside the combustion chamber to measure fresh air quantity, then measurement accuracy improves, but device complexity and cost increase
Solution Approach 1:
The patent introduces an intermediary approach by using readily available sensors (temperature and time since start-up) to infer valve timing variations, which then serve as the basis for correcting fresh air quantity estimation. Instead of directly measuring pressure and temperature inside the combustion chamber, the system uses external measurements and computational models to achieve the same objective with simpler hardware.
Solution Approach 2:
The patent substitutes complex sensing hardware (pressure and temperature sensors inside the combustion chamber) with a computational approach using existing sensors and mathematical models. The ECU calculates fresh air quantity by integrating valve timing corrections with standard engine parameters, eliminating the need for intrusive internal sensors and reducing overall system complexity.
Data Source
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AI summary
The invention relates to a method for estimating an amount of fresh air, taken into an engine cylinder combustion chamber during an engine cycle, from a model parameterized with angles for opening and closing intake and exhaust valves. Said method comprises calibrating (120) the model to a nominal temperature for operating the engine, said calibration also involving setting the value of the opening and closing angles. During operation of the engine at a temperature different from the nominal temperature, the method comprises correcting (126) the set opening and closing angles on the basis of an estimate of the distribution clearance between the valves and the rocker arms thereof.