Variable Valve Timing Control Device Sensor Diagnosis
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Solution Overview
Problem
In variable valve timing mechanisms, errors in calculated actual valve timing values during low engine rotation speeds can lead to erroneous diagnosis of motor angle sensor abnormalities, risking false normality detection.
Innovation Solution
A control device and method that include a first measuring unit for rotational phase measurement based on cam and crank angle signals, a second unit for measuring phase change over time using motor angle signals, and a diagnosing unit to assess pulse patterns and determine sensor normality, reducing erroneous diagnoses by verifying signal integrity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the threshold for abnormality diagnosis is set to ensure accurate detection of motor angle sensor faults, then the reliability of fault detection is improved, but the risk of erroneous diagnosis increases when actual valve timing values contain errors during low engine rotation speeds
Solution Approach 1:
The control device determines whether the cam angle signal and crank angle signal have prescribed pulse patterns before performing abnormality diagnosis of the motor angle sensor. This preliminary verification ensures that the actual valve timing calculation is based on valid signal data, preventing erroneous diagnosis when signals contain errors during low engine rotation speeds.
Solution Approach 2:
The control device uses feedback from the pulse pattern verification to control whether the abnormality diagnosis is executed. When the prescribed pulse patterns are confirmed, the diagnosis proceeds; when not confirmed, the diagnosis is withheld. This feedback mechanism dynamically adjusts the diagnosis execution based on signal quality, resolving the contradiction between detection reliability and measurement precision.
2Object-affected harmful factors
If the threshold for abnormality diagnosis is set to a high value to prevent erroneous diagnosis during low rotation speeds, then false abnormality detection is reduced, but the ability to detect actual motor angle sensor abnormalities deteriorates
Solution Approach 1:
Instead of adjusting the diagnosis threshold, the control device performs a preliminary verification of the pulse patterns in the cam angle signal and crank angle signal. This preliminary action ensures that diagnosis is only performed when the signals are valid, eliminating false abnormality detection without compromising the detection capability for actual faults.
Solution Approach 2:
The pulse pattern verification acts as an intermediary condition between the actual valve timing calculation and the abnormality diagnosis. This intermediary step filters out invalid signal conditions that would cause false detection, while allowing valid signals to proceed to diagnosis, thus resolving the contradiction between reducing false detection and maintaining detection capability.
3Duration of action of stationary object
If abnormality diagnosis is performed based on actual valve timing values during low engine rotation speeds, then continuous monitoring is improved, but the accuracy of diagnosis deteriorates due to errors in calculated valve timing values
Solution Approach 1:
The control device performs a preliminary verification of the pulse patterns in the cam angle signal and crank angle signal before executing the abnormality diagnosis. This preliminary action ensures that diagnosis is only performed when the signals are valid, preventing inaccurate diagnosis during low rotation speeds while maintaining continuous monitoring coverage across all operating conditions.
Solution Approach 2:
The control device dynamically adjusts the execution of abnormality diagnosis based on the verification results of pulse patterns. When the engine operates at low rotation speeds with valid signals, diagnosis is performed; when signals are invalid, diagnosis is withheld. This dynamic adjustment ensures continuous monitoring coverage while maintaining diagnosis accuracy across varying operating conditions.
Data Source
AI summary
In a control device and a control method for a variable valve timing mechanism according to the present invention, the rotational phase of a camshaft is measured based on the cam angle signal and crank angle signal upon receiving each pulse of the cam angle signal, and the rotational phase change over time within a period of the cam angle signal is measured based on the motor angle signal. It is decided whether the cam angle signal and/or crank angle signal has a prescribed pulse pattern at a diagnostic timing that comes after the last pulse of the cam angle signal. When this decision result is positive, it is then decided whether the motor angle sensor operates normally or abnormally based on the rotational phase and the amount of rotational phase change that are measured when the last pulse of the cam angle signal is received before the diagnostic timing.