Camshaft Sensor Calibration Using Dynamic Threshold Adjustment
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Solution Overview
Problem
Existing camshaft sensor calibration methods fail to achieve the required accuracy due to 'out-of-roundness' defects in the target and airgap variations between the sensor and target, leading to erroneous position determination of engine cylinders.
Innovation Solution
A method that continuously measures magnetic field values during a camshaft revolution, calculates and adjusts switching thresholds based on new maximum and minimum values, and updates averages to account for changes in target geometry, thereby improving signal accuracy and correcting for 'out-of-roundness' and airgap defects.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a fixed switching threshold (e.g., 75% of amplitude) is used for sensor calibration, then the calibration process is simple and fast, but measurement precision deteriorates due to out-of-roundness defects and airgap variations in the target
Solution Approach 1:
The patent applies dynamics by transitioning from a fixed switching threshold to a dynamic threshold adjustment mechanism. The system continuously adapts the switching threshold based on real-time signal characteristics during target rotation, allowing the threshold to vary with each tooth passage. This dynamic adaptation compensates for out-of-roundness defects and airgap variations, resolving the contradiction between simple fixed-threshold calibration and precise variable-condition measurement.
Solution Approach 2:
The patent implements parameter changes by modifying the switching threshold parameter based on observed signal characteristics. The system measures the magnetic field signal during target rotation, detects variations caused by target imperfections, and adjusts the switching threshold parameter accordingly. This parameter adaptation enables accurate position determination despite manufacturing defects, resolving the precision issue while maintaining calibration efficiency.
2Adaptability or versatility
If the sensor and target are kept at variable separation distances, then the system is more tolerant of manufacturing variations, but measurement precision deteriorates due to phase shift in the magnetic field signal
Solution Approach 1:
The patent applies feedback by continuously monitoring the magnetic field signal characteristics during target rotation and using this information to adjust the switching threshold. The system measures the actual signal amplitude and timing, compares it against expected values, and compensates for phase shifts caused by variable airgaps. This feedback mechanism maintains measurement precision despite variations in sensor-target separation, resolving the contradiction between adaptability and precision.
3Ease of operation
If traditional calibration methods are used that assume perfect target geometry, then the calibration process is straightforward, but reliability deteriorates due to out-of-roundness defects causing non-detection of teeth
Solution Approach 1:
The patent implements self-service by enabling the calibration system to automatically detect and compensate for its own target imperfections. During the calibration process, the system measures the actual signal characteristics, identifies out-of-roundness defects and airgap variations, and autonomously adjusts the switching threshold without requiring manual intervention or perfect target geometry. This self-correcting mechanism maintains calibration simplicity while significantly improving tooth detection reliability.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The method delivers a more accurate signal output by dynamically adjusting switching thresholds, enhancing the precision of cylinder position determination and mitigating non-detection issues caused by target geometry imperfections and airgap variations.
Implementation Method 1
a magnetic field sensor placed in proximity to the target to detect the magnetic field variations induced by the passage of the teeth of the target in proximity to the sensor
Data Source
AI summary
A method for automatic calibration of an engine camshaft sensor, the engine including at least one camshaft, a coded toothed target associated with this camshaft and a magnetic field sensor placed in the vicinity of the target to detect magnetic field variations induced by passage of the target's teeth in the vicinity of the sensor, the sensor delivering an electrical signal representative of teeth and gaps of the target depending on a predetermined switching threshold as a function of the magnetic field's amplitude, the method continuously measuring the value of the magnetic field. The method calculating switching thresholds of the leading edges of the teeth over a new turn of the target to improve the precision of detection of the leading edges of the teeth.