Intake Oxygen Sensor Diagnostics via EGR Valve Position
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Solution Overview
Problem
Current diagnostic systems fail to accurately detect malfunctions in intake oxygen sensors due to low pressure drop across the EGR valve, leading to inadequate feedback for controlling the EGR system.
Innovation Solution
A diagnostic system that includes an intake oxygen sensor and an EGR valve position sensor, with a controller performing non-intrusive and intrusive rationality diagnostics by measuring oxygen concentration differences across predetermined EGR valve positions to detect sensor malfunctions, ensuring accurate measurement verification.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If current diagnostic systems are used to detect intake oxygen sensor malfunctions, then the system structure remains simple, but the measurement precision deteriorates due to low pressure drop across the EGR valve
Solution Approach 1:
The diagnostic approach is segmented into two distinct methods: non-intrusive diagnostic that monitors existing EGR valve position changes, and intrusive diagnostic that actively commands EGR valve to specific positions. This segmentation allows the system to choose between simplicity and accuracy based on diagnostic needs.
Solution Approach 2:
The system performs preliminary checks by monitoring oxygen concentration changes during normal EGR valve position transitions before resorting to more complex intrusive diagnostics. This preliminary action allows accurate detection when possible while avoiding unnecessary system complexity.
2Reliability
If non-intrusive rationality diagnostic is performed during normal EGR operation, then the system complexity remains low, but the reliability deteriorates when EGR valve position changes are insufficient
Solution Approach 1:
The diagnostic system dynamically switches between non-intrusive and intrusive diagnostic modes based on operating conditions. When non-intrusive diagnostic proves insufficient (oxygen concentration change below threshold), the system transitions to intrusive diagnostic that actively controls EGR valve positions, ensuring reliable detection across all operating conditions.
Solution Approach 2:
The system uses feedback from oxygen concentration measurements to determine whether non-intrusive diagnostic was successful. If the oxygen concentration change does not exceed the threshold, the feedback triggers a transition to intrusive diagnostic mode, ensuring reliable malfunction detection.
3Measurement precision
If intrusive rationality diagnostic is performed by commanding EGR valve to predetermined positions, then the measurement precision improves, but the productivity deteriorates due to additional diagnostic steps
Solution Approach 1:
The intrusive diagnostic performs partial action by commanding EGR valve to only two predetermined positions (low and high) rather than testing all possible positions. This partial action is sufficient to verify sensor functionality while minimizing the time penalty compared to comprehensive testing.
Solution Approach 2:
The diagnostic system performs intrusive diagnostic periodically or on-demand rather than continuously. This periodic action reduces the overall impact on productivity while maintaining measurement precision when diagnostics are executed.
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 system provides robust and accurate detection of intake oxygen sensor malfunctions, preventing false service trips and ensuring reliable engine operation by differentiating between acceptable and unacceptable oxygen concentration ranges.
Implementation Method 1
an intake oxygen sensor configured to measure an oxygen concentration in an induction system of an engine
Data Source
AI summary
Rationality diagnostic techniques for an intake oxygen sensor are utilized to detect sensor malfunction. A non-intrusive diagnostic technique includes passively detecting when an exhaust gas recirculation (EGR) valve position crosses low/high position thresholds, whereas an intrusive diagnostic technique includes actively commanding the EGR valve to predetermined low/high positions. During a period after the EGR valve position reaches/crosses at least one of the low/high positions/position thresholds, respectively, maximum and minimum intake oxygen concentration is monitored. When the EGR valve position has crossed both the low/high positions/position thresholds and a difference between the maximum and minimum oxygen concentrations is less than a respective difference threshold, a malfunction of the intake oxygen sensor is detected. A malfunction indicator lamp (MIL) could be set to indicate the malfunction. The intrusive technique is additionally or alternatively implemented, such as part of a verification or backup to the non-intrusive technique.