Variable Valve Timing Phase Detection for Engine Speed Adaptation
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing variable valve timing apparatuses face challenges in accurately detecting actual valve timing, especially at varying engine speeds, leading to decreased control accuracy and increased computational load, particularly in cold climates or low engine speed conditions.
Innovation Solution
A variable valve timing apparatus incorporating an actuator, changing mechanism, and detectors to detect crankshaft, camshaft, and actuator rotation angles, with a phase detecting portion that selects between two calculating methods based on engine speed to optimize detection accuracy without excessive computational load, and includes abnormality processing to prevent erroneous control.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the amount of change in valve timing is continuously calculated based on the difference in rotation speed between the motor and the camshaft, then the detection accuracy of actual valve timing is improved, but the computational load increases
Solution Approach 1:
The patent dynamically switches between two detection methods based on engine speed conditions. At low engine speeds where continuous calculation is necessary for accuracy, the system uses the motor-camshaft rotation speed difference method. At high engine speeds where calculation burden becomes excessive, it transitions to using only cam angle sensor signals. This dynamic adaptation resolves the contradiction by adjusting the detection strategy according to operating conditions.
Solution Approach 2:
The system changes the detection parameter strategy based on engine speed thresholds. When engine speed is below a predetermined threshold, it uses the accumulated amount of change in rotation phase difference as the detection parameter. When engine speed exceeds the threshold, it switches to using only the cam angle signal. This parameter change approach allows the system to maintain detection accuracy while avoiding excessive computational load at different operating points.
2Measurement precision
If the cam angle signal output frequency is increased to improve detection accuracy at high engine speeds, then the detection accuracy is improved, but the computational load and processing requirements increase
Solution Approach 1:
The patent applies partial action by using only the cam angle sensor signal for valve timing detection at high engine speeds, rather than continuously processing both cam angle and motor rotation phase data. This partial use of available sensors reduces computational requirements while maintaining sufficient detection accuracy for high-speed operation, avoiding the need for excessive signal processing.
3Reliability
If the engine operates in cold climates or at startup, then the hydraulic pressure decreases and response slows down, but using an electric motor as actuator requires accurate detection at low engine speeds where detection accuracy is difficult to achieve
Solution Approach 1:
The system uses feedback control by continuously monitoring the actual valve timing detection accuracy and adjusting the detection method accordingly. At low engine speeds during cold operation or startup, the system switches to the accumulated rotation phase difference calculation method, which provides better feedback accuracy when standard sensor methods become unreliable due to unstable engine operation and low sensor signal frequency.
Data Source
Figure 1
Figure 2
Figure 3
AI summary
When the engine speed is high (determination of YES at S100), actual intake valve phase (IV(q)) is calculated based on rotation phase difference between rotation angles of crankshaft and camshaft, detected by using a crank angle signal and a cam angle signal, and actual valve timing is detected therefrom (S110). When the engine speed is low (determination of NO at S100) and the crank angle signal and cam angle signal are unstable, an amount of change in camshaft rotation phase (dIV(q)) by the VVT mechanism in accordance with the operation amount of actuator detected by a motor rotation angle signal is calculated successively (S120), and based on an accumulation of the amount of change (dIV(q)), the actual intake valve phase (IV(q)) is calculated, and the actual valve timing is detected (S130).