Engine Control Device Abnormal Crank Angle Signal Handling
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Solution Overview
Problem
The accuracy of variable valve timing control in internal combustion engines deteriorates when the crank angle signal is abnormal, particularly during engine start-up, due to the lower frequency of engine rotation speed determination based on intake or exhaust cam signals compared to the crank angle signal.
Innovation Solution
A control device that adjusts the variable intake and exhaust valve timing mechanisms based on the crank angle signal and cam signals, setting the relative phase angle of the exhaust camshaft to a reference phase when the crank angle signal is abnormal, ensuring the phase difference between the exhaust and intake cam signals is minimized during start-up, thereby maintaining control accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the control device determines engine rotation speed based on intake or exhaust cam signal when crank angle signal is abnormal, then the control can continue, but the determination frequency is lower and accuracy deteriorates especially during start-up
Solution Approach 1:
The patent applies dynamics by making the determination frequency adaptive - using high frequency (crank angle signal) during normal operation and switching to low frequency (cam signal) only when necessary. The system dynamically adjusts the control strategy based on the operational state and signal availability, optimizing both reliability and precision under different conditions.
2Reliability
If the control device uses intake cam signal and exhaust cam signal to control variable valve timing mechanisms when crank angle signal is abnormal, then control can be maintained, but the accuracy of relative phase angle determination deteriorates during start-up
Solution Approach 1:
The patent changes the parameter of phase difference constraint based on operational state. During start-up, it constrains the phase difference between intake and exhaust cam signals to within a predetermined range, while during normal operation this constraint is relaxed. This dynamic parameter adjustment maintains control accuracy despite using lower-frequency cam signals.
3Adaptability or versatility
If the phase difference between exhaust cam signal and intake cam signal is large during start-up, then the control range is flexible, but the determination accuracy of relative phase angles deteriorates
Solution Approach 1:
The patent applies local quality by imposing specific constraints on the phase difference between cam signals only during the start-up period, while allowing greater flexibility during normal operation. This localized constraint ensures accurate phase angle determination when it matters most (during start-up) without unnecessarily limiting control flexibility during other operational phases.
Data Source
AI summary
In a control device and a control method for an internal combustion engine according to the present invention, when a crank angle signal is behaving abnormally, a phase angle of an exhaust camshaft relative to a crankshaft is set to a reference phase angle, and a phase angle of an intake camshaft relative to the crankshaft is determined based on an intake cam signal and an exhaust cam signal. Furthermore, the phase difference between the exhaust cam signal generated when the relative phase angle of the exhaust camshaft is set to the reference phase angle and the intake cam signal generated when the relative phase angle of the intake camshaft is set to a target value is greater after a start-up of the internal combustion engine than during the start-up.