Variable Valve Timing Control Apparatus Reference Phase Learning
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Solution Overview
Problem
The accuracy of calculating and controlling variable valve timing in internal combustion engines is compromised due to reduced frequency of learning the reference phase, especially with the introduction of the Atkinson cycle, which enlarges the variable range of the VCT phase, leading to prolonged intervals between learning and potential inaccuracies.
Innovation Solution
A variable valve timing control apparatus that includes means to determine if a learning requirement for the reference phase exists, and if so, enlarges the operation area where the target VCT phase is set into the reference phase, allowing for increased opportunities to learn the reference phase, while also controlling actuators like the EGR device and throttle to maintain combustion stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If the variable range of the VCT phase is enlarged to improve engine output and gas mileage through Atkinson cycle, then the adaptability of the engine is improved, but the frequency of learning the reference phase is reduced, leading to lower measurement precision of the actual VCT phase
Solution Approach 1:
The patent dynamically adjusts the target VCT phase based on engine operating conditions. When the actual VCT phase is close to the reference phase, the control apparatus actively changes the target VCT phase to force the system away from the reference point, thereby creating opportunities for reference phase learning. This dynamic adjustment ensures that the learning process occurs frequently enough to maintain measurement precision while still allowing the VCT phase to vary across its full operational range for adaptability.
Solution Approach 2:
The control apparatus continuously monitors the actual VCT phase and compares it with the reference phase. Based on this feedback, the system determines whether the actual VCT phase is sufficiently close to the reference phase and accordingly adjusts the target VCT phase. This feedback mechanism ensures that the system maintains awareness of its reference point while allowing operational flexibility, resolving the contradiction between adaptability and measurement precision.
2Measurement precision
If the target VCT phase is frequently changed to increase learning opportunities, then the measurement precision is improved, but the combustion state may deteriorate due to changes in intake air amount
Solution Approach 1:
The patent applies different control strategies based on the local operating conditions. When the actual VCT phase is close to the reference phase, the system actively changes the target VCT phase to enable learning. However, when the actual VCT phase is far from the reference phase, the system maintains the target VCT phase to avoid unnecessary disturbances to combustion. This localized control approach ensures that reference phase learning occurs without compromising overall combustion stability.
Solution Approach 2:
The control apparatus carefully manages parameter changes by only adjusting the target VCT phase when necessary for reference phase learning. The system monitors the difference between actual and reference phases and only initiates target phase changes when this difference is within a predetermined threshold. This selective parameter change approach minimizes disruptions to combustion while still enabling sufficient learning opportunities.
Data Source
AI summary
A variable valve timing control apparatus includes a variable valve timing device and a valve timing controller to control the variable valve timing device in a manner that an actual VCT phase coincides with a target VCT phase. When the target VCT phase is set into a predetermined phase, learning means learn the predetermined phase as a reference phase. When determining means determine that there is a learning requirement of the reference phase, enlarging means enlarge an engine operation area where the target VCT phase is set into the reference phase by shifting the target VCT phase to the reference phase in an area where the target VCT phase is close to the reference phase.