Fuel Vapor Canister Temperature Refueling Detection
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Solution Overview
Problem
Refueling events can skew leak detection results in evaporative emission control systems, leading to false positives or negatives during diagnostics, especially when sensors like fuel tank pressure sensors are unreliable or unavailable.
Innovation Solution
Monitoring temperature changes in the fuel vapor canister to detect refueling events, allowing for the discontinuation of leak diagnostics and preventing false results, even in the absence of a fuel tank pressure sensor or when it is degraded.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a fuel tank pressure sensor is used to detect refueling events, then refueling detection capability is improved, but false refueling determinations occur during towing, trunk slamming, or vehicle shaking conditions
Solution Approach 1:
The patent introduces a canister temperature sensor as an intermediary detection mechanism to detect refueling events. Instead of directly measuring fuel tank pressure which is susceptible to false signals from external disturbances, the system uses temperature changes in the canister as an indirect indicator of refueling, which occurs when fresh fuel contacts the canister and causes detectable temperature changes.
Solution Approach 2:
The patent replaces the mechanical/pressure-based detection system with a thermal-based detection system. By substituting pressure sensor measurements with temperature sensor measurements, the system achieves more reliable refueling detection that is not affected by mechanical disturbances such as towing, trunk slamming, or vehicle shaking.
2Measurement precision
If leak diagnostics are performed during engine off conditions, then diagnostic accuracy is improved by reducing noise factors, but refueling events during diagnostics cause false pass or false fail results
Solution Approach 1:
The patent implements a feedback mechanism where the canister temperature sensor continuously monitors temperature during leak diagnostics. When a temperature change indicating refueling is detected, the system provides feedback to abort or pause the leak diagnostics, preventing false diagnostic results. This feedback loop ensures that diagnostics are only performed when conditions are appropriate.
Solution Approach 2:
The patent performs preliminary detection of refueling conditions by monitoring canister temperature before completing leak diagnostics. By detecting temperature changes that indicate refueling is occurring, the system can preliminarily determine that diagnostics should be aborted, preventing false results before they occur.
3Volume of stationary object
If the carbon canister capacity is limited, then system size is reduced, but engine running manifold vacuum is required to desorb vapor which increases system complexity
Solution Approach 1:
The patent utilizes dynamic operation of the purge valve and canister system, switching between adsorption mode during refueling and desorption mode during engine operation. The system dynamically adjusts based on operating conditions, using engine manifold vacuum when available to desorb vapors, and relying on passive adsorption during refueling events when the engine is off.
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
Effectively identifies refueling events and aborts leak detection algorithms, ensuring accurate diagnostics by using temperature changes in the fuel vapor canister to differentiate between refueling and other noise factors, thereby improving the reliability of emission control system diagnostics.
Implementation Method 1
a carbon canister is also coupled to the fuel tank to adsorb fuel vapors under some conditions when the internal combustion engine is not running
Implementation Method 2
during refueling, vapors dispensed by a refueling pump may be adsorbed in the canister leading to a temperature rise in the canister
Data Source
AI summary
Methods and systems for detecting a refueling event for diagnostics are disclosed. In one example approach a method comprises discontinuing leak diagnostics in response to a temperature change in a fuel vapor canister coupled to a fuel tank in an emission control system while the leak diagnostics are being performed in the emission control system.