EVAP Degradation Localization via Spud Valve Positioning
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Solution Overview
Problem
Existing evaporative emissions control (EVAP) systems face challenges in accurately identifying and pinpointing the location of degradations, often leading to costly and excessive in-shop testing, as current methods cannot distinguish between improper sealing of the fuel cap and damage within the EVAP and fuel systems.
Innovation Solution
A method is introduced that involves conducting diagnostic routines under two distinct conditions based on the position of the spud valve within the fuel tank, comparing results to identify potential degradations in the refueling system, thereby pinpointing the location of the issue.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a single diagnostic routine is used to detect degradation in the EVAP system, then the detection capability is simple and quick, but the location precision of the degradation cannot be determined
Solution Approach 1:
The diagnostic routine is segmented into two distinct conditions: first condition with spud valve submerged in fuel, and second condition with spud valve in vapor space. Each condition tests a different pathway (recirculation tube only vs. filler neck and recirculation tube), allowing localization of degradation by comparing results between the two segments.
Solution Approach 2:
The system dynamically changes the testing condition by varying the fuel level to move the spud valve between submerged and exposed positions. This dynamic adjustment allows the same diagnostic system to test different pathways sequentially, improving location precision without requiring multiple permanent test configurations.
2Measurement precision
If in-shop EVAP system degradation testing is performed to pinpoint the location of degradation, then accurate location identification is achieved, but the time and cost increase significantly
Solution Approach 1:
The EVAP system performs self-diagnosis by automatically conducting the two-condition diagnostic routine onboard the vehicle. The controller autonomously monitors pressure changes during both conditions and compares results to determine degradation location, eliminating the need for external shop testing and reducing both time and cost.
Solution Approach 2:
The system performs preliminary degradation detection and location identification using the two-condition routine before any shop testing is required. By preliminarily narrowing down the degradation location to either the recirculation tube or filler neck area, the system prevents unnecessary comprehensive shop testing, saving time and resources.
3Reliability
If the spud valve is always submerged in fuel, then the recirculation tube pathway is consistently tested, but the filler neck pathway cannot be evaluated for degradation
Solution Approach 1:
The system dynamically adjusts the fuel level to change the spud valve position between submerged and exposed states. This allows the diagnostic routine to adaptively test different pathways: when submerged, it tests the recirculation tube; when exposed, it tests the filler neck pathway, providing comprehensive coverage.
Solution Approach 2:
The diagnostic system changes the physical parameter of fuel level to alter the spud valve position and thereby change which pathway is being tested. By varying this parameter, the system can selectively evaluate different components (recirculation tube vs. filler neck) for degradation.
Data Source
AI summary
Methods and systems are provided for indication of a degradation in an EVAP and/or fuel system. In one example, a method for indication of a presence or absence of a degradation in a refueling system may include vacuum pull-down and pressure bleed-up tests being carried out based on a state of submersion of a spud valve in liquid fuel in a fuel tank.