Internal EGR Calculation Correction for Variable Valve Duration Engines
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Solution Overview
Problem
Existing engine technologies fail to accurately calculate internal exhaust gas recirculation (EGR) amounts when using continuously variable valve duration apparatuses, leading to inaccuracies in fuel injection and engine performance due to changes in valve duration, which affect the effective area of valve overlap and consequently the flow rate of gases.
Innovation Solution
A method and apparatus that calculate the internal EGR amount by considering the changed valve duration, using a correction factor based on the altered valve profile to adjust the basic backflow gas amount, ensuring accurate determination of residual and backflow gases during valve overlap periods, thereby optimizing fuel injection and engine efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If continuously variable valve duration apparatus is used to change valve duration, then valve duration control flexibility is improved, but internal EGR calculation accuracy deteriorates
Solution Approach 1:
The patent applies parameter changes by introducing a correction factor that modifies the basic backflow gas amount calculation based on the actual valve duration. The correction factor is determined by the ratio of actual valve duration to basic valve duration, and this parameter adjustment compensates for the calculation errors introduced by variable valve duration operation, thereby maintaining calculation accuracy while preserving control flexibility.
Solution Approach 2:
The patent implements feedback by calculating the correction factor based on the actual valve duration obtained from the continuously variable valve duration apparatus, and using this feedback to adjust the internal EGR amount calculation. The controller continuously monitors the valve duration and adjusts the correction factor accordingly, creating a closed-loop system that maintains accuracy despite variable operating conditions.
2Shape
If valve duration is changed by continuously variable valve duration apparatus, then valve profile is improved, but effective area of valve overlap calculation accuracy deteriorates
Solution Approach 1:
The patent changes the calculation parameter by introducing a correction factor that accounts for the altered valve profile. The correction factor is calculated as the ratio of actual valve duration to basic valve duration, and this parameter modification adjusts the effective area calculation to reflect the changed valve overlap conditions, thereby maintaining accuracy despite profile changes.
3Ease of manufacture
If basic backflow gas amount calculation is used without correction, then calculation simplicity is improved, but fuel injection accuracy deteriorates
Solution Approach 1:
The patent applies preliminary action by pre-calculating the correction factor based on the valve duration ratio before performing the final internal EGR calculation. The correction factor is determined in advance from the ratio of actual to basic valve duration, and this pre-computed factor is then applied to the basic backflow gas amount, simplifying the overall calculation process while improving accuracy.
Solution Approach 2:
The patent modifies the calculation by introducing a correction factor parameter that adjusts the basic backflow gas amount. This parameter change transforms the simple but inaccurate basic calculation into a more accurate calculation that accounts for variable valve duration, thereby improving fuel injection accuracy while maintaining relative calculation simplicity.
Data Source
AI summary
A method and apparatus for calculating an internal exhaust gas recirculation (EGR) amount of an engine include a continuously variable valve duration (CVVD) apparatus. The internal EGR amount is calculated by correcting a backflow gas amount based on a valve duration changed by operation of the continuously variable valve duration apparatus during valve overlap of an intake valve or an exhaust valve.