Adaptive Exhaust Gas Sensor Signal Analysis for Valve Stroke Defect Detection
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Solution Overview
Problem
Existing methods for diagnosing defects in internal-combustion engine valve stroke adjusting systems are unreliable and prone to false positives, especially in multi-cylinder engines with only one continuous lambda sensor, due to varying operating conditions and sensitivity issues.
Innovation Solution
The method involves determining the spread width of the exhaust gas sensor's output signal and comparing it to a reference value, which is adjusted based on operating parameters, to detect defects reliably, even with a single sensor, by using techniques such as spread width measurement, rain flow classification, and standard deviation analysis.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a low defect detection threshold value is used to detect individual cylinder defects, then the sensitivity of defect detection is improved, but the probability of false positive detections increases
Solution Approach 1:
The patent applies dynamics by making the reference value adaptive rather than fixed. The reference value is determined based on the currently active valve stroke position (first or second stroke), allowing the defect detection threshold to dynamically adjust according to operating conditions. This resolves the contradiction by enabling sensitive defect detection while maintaining reliability across different operational states.
Solution Approach 2:
The patent changes the parameter of the reference value based on the valve stroke position. When the valve stroke is changed between first and second positions, the reference value is accordingly adjusted to match the expected spread width characteristics of that specific stroke position. This parameter adaptation allows accurate defect detection without false positives caused by using inappropriate reference thresholds.
2Reliability
If multiple exhaust gas sensors are used to improve defect detection reliability, then the reliability of defect detection is improved, but the device complexity and cost increase
Solution Approach 1:
The patent applies self-service by enabling a single exhaust gas sensor to perform the diagnostic function that would traditionally require multiple sensors. By analyzing the spread width of the sensor signal and comparing it against adaptive reference values based on valve stroke position, the system achieves reliable defect detection using only one sensor, thereby reducing device complexity and cost.
Solution Approach 2:
The patent uses parameter changes in the analysis methodology - specifically measuring the spread width parameter of the sensor signal and comparing it against reference values that change according to valve stroke position. This sophisticated analysis of single-sensor data compensates for the lack of multiple sensors, achieving the same diagnostic reliability with reduced hardware complexity.
3Productivity
If the valve stroke is adjusted to optimize charge for different operating conditions, then the engine efficiency is improved, but the complexity of the valve stroke adjusting system increases
Solution Approach 1:
The patent applies dynamics by implementing an adjustable valve stroke system that can dynamically change between a first valve stroke position and a second valve stroke position based on operating conditions. This dynamic adjustment optimizes the charge for different engine operating points, improving productivity while the associated control system manages the complexity.
Solution Approach 2:
The valve stroke adjusting system serves multiple functions: it optimizes engine charge for different operating conditions, enables diagnostic measurements at different stroke positions, and provides the basis for the defect detection method. This multi-functionality justifies the added complexity by delivering multiple benefits from a single system.
Data Source
AI summary
In a method for diagnosing a charge cycle valve stroke adjusting system of an internal-combustion engine having at least one exhaust gas sensor which supplies an output signal continuously varying with an exhaust gas constituent, the spread width of the output signal is determined, and compared with a reference value. Defects of the valve stroke adjusting system are detected on the basis of the comparison.