Camshaft Sensor Calibration for Engine Timing Precision
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Solution Overview
Problem
Camshaft sensors face precision issues due to 'out-of-roundness' defects in the target's geometry and varying air gaps, leading to erroneous signal detection and potential non-detection of teeth, especially when teeth have different heights and spacings, causing phase shifts and parasitic pulses in the electrical signal.
Innovation Solution
A method for automatically calibrating the camshaft sensor by continuously measuring the magnetic field and adjusting the switching threshold based on a hysteresis threshold dependent on the new maximum value, ensuring the electrical signal remains in a high state until the hysteresis threshold is crossed, thereby avoiding false detections and recalculating the switching threshold after each tooth passage to correct for 'out-of-roundness' and air gap defects.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If a fixed switching threshold is used for detecting tooth passages, then the detection method is simple, but detection precision deteriorates due to out-of-roundness and varying air gaps
Solution Approach 1:
The patent applies dynamics by transitioning from a fixed switching threshold to a dynamic threshold that adapts to varying magnetic field conditions. The switching threshold is continuously adjusted based on the detected magnetic field amplitude and hysteresis characteristics, allowing the system to maintain high detection precision despite out-of-roundness and air gap variations while preserving operational simplicity through automated adaptation.
Solution Approach 2:
The patent implements parameter changes by modifying the switching threshold parameter in response to detected magnetic field variations. The threshold is dynamically recalculated based on the amplitude of the magnetic field signal and hysteresis measurements, enabling the system to compensate for geometric defects and maintain accurate tooth passage detection without requiring complex mechanical adjustments.
2Measurement precision
If the switching threshold is dynamically adjusted based on magnetic field amplitude, then detection precision improves, but device complexity increases
Solution Approach 1:
The patent applies self-service by enabling the sensor system to automatically adjust its own switching threshold without external intervention. The system uses its detected magnetic field signal to autonomously calculate and update the threshold based on amplitude and hysteresis characteristics, eliminating the need for complex external calibration mechanisms while maintaining high detection precision.
Solution Approach 2:
The patent implements feedback by using the detected magnetic field signal to continuously update the switching threshold. The system measures the magnetic field amplitude and hysteresis, then feeds this information back to adjust the threshold dynamically, creating a closed-loop system that maintains optimal detection precision without requiring complex open-loop control mechanisms.
3Reliability
If a hysteresis threshold is introduced to avoid false detections, then reliability improves, but response time increases
Solution Approach 1:
The patent applies partial action by implementing a selective hysteresis mechanism that is activated only when necessary to eliminate parasitic pulses. The hysteresis threshold is applied conditionally based on the detected signal characteristics, allowing the system to maintain high reliability by filtering false detections while minimizing response time delays by not applying hysteresis continuously to all signal transitions.
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
This approach eliminates parasitic pulses and ensures accurate detection of tooth passages, improving the precision of cylinder position determination in the engine cycle by dynamically adjusting the switching threshold in response to varying magnetic field amplitudes, thus enhancing the reliability of camshaft timing, especially in variable valve timing systems.
Implementation Method 1
a magnetic field sensor placed near the target to detect variations in magnetic field values induced by the passage of the teeth of the target in proximity to the sensor
Data Source
AI summary
A method for automatically calibrating an engine camshaft sensor, the sensor measuring variations in magnetic field value and delivering an electrical signal having a high state after the passage of the values of the magnetic field above the switching threshold on a rising edge and a low state after the passage of the values of the magnetic field below the switching threshold on a falling edge. After the passage of the values of the magnetic field above the switching threshold and measuring a new maximum value, the electrical signal remains in a high state as long as the magnetic field values are higher than a hysteresis threshold, which is dependent on the amplitude of the magnetic field calculated with the measured new maximum value; after the passage of the values of the magnetic field below the hysteresis threshold, a new switching threshold is calculated according to the new maximum value.