Fuel System Leak Detection Threshold Adjustment
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Solution Overview
Problem
Existing fuel system leak detection methods in vehicles are prone to false failures or passes due to temperature and pressure variations caused by factors like engine run time, parking surface temperature, and environmental conditions, particularly in hybrid vehicles where heat rejection is low, leading to inadequate vacuum generation for leak tests.
Innovation Solution
Adjusting the diagnostic threshold for fuel system leaks based on the inferred distance between the fuel tank and the ground surface, accounting for ground surface temperature and cargo load, to enhance the accuracy of leak detection by dynamically modifying the threshold pressure or vacuum.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If EONV approaches are used for leak detection, then fuel system leaks can be identified, but false failures or false passes occur due to temperature and pressure variations
Solution Approach 1:
The patent dynamically adjusts the diagnostic threshold based on fuel tank temperature and inferred ground surface temperature. Instead of using a fixed threshold, the system modifies the pressure or vacuum threshold according to thermal conditions, thereby maintaining measurement precision across varying environmental temperatures while preserving reliable leak detection
Solution Approach 2:
The system continuously monitors fuel tank temperature and ground surface temperature (inferred from vehicle weight and ambient conditions) to dynamically adjust the diagnostic threshold. This feedback mechanism ensures that the threshold adapts to current thermal conditions, preventing false positives and negatives while maintaining accurate leak detection
2Reliability
If vacuum generation relies on fuel tank cooling, then leak detection can be performed, but insufficient vacuum is generated in hybrid vehicles with low engine run times
Solution Approach 1:
The patent modifies the diagnostic approach by adjusting the diagnostic threshold rather than relying solely on achieving a fixed vacuum level. This allows the system to perform accurate leak detection even when vacuum generation is insufficient due to short engine run times in hybrid vehicles, as the threshold adapts to the actual thermal and pressure conditions
Solution Approach 2:
The system uses inferred ground surface temperature (derived from vehicle weight and ambient conditions) to compensate for insufficient vacuum generation. By self-adjusting the diagnostic threshold based on available data, the system ensures reliable leak detection without requiring extended engine operation to generate adequate vacuum
3Measurement precision
If fixed diagnostic thresholds are used, then diagnostic simplicity is maintained, but accuracy degrades due to environmental variations
Solution Approach 1:
The patent implements dynamic threshold adjustment based on fuel tank temperature and inferred ground surface temperature. The control system modifies the diagnostic threshold as a function of these thermal parameters, maintaining high diagnostic accuracy while managing complexity through algorithmic threshold calculation rather than physical system complexity
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 reduces the occurrence of false passes and false failures in fuel system leak diagnostics by compensating for the proximity of the fuel tank to the ground, thereby improving the accuracy of leak detection results.
Implementation Method 1
as a fuel tank cools down, a vacuum is generated therein
Implementation Method 2
how much heat was rejected from the running engine to the fuel tank
Data Source
AI summary
Methods and systems are provided for a fuel system. In one example, a method includes adjusting a threshold of a diagnostic based on a distance between a fuel tank and a ground surface. The distance is inferred based on a vehicle weight.