Fuel Tank Pressure Sensor Offset Determination Without Vapor Release
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Solution Overview
Problem
Existing methods for determining the inherent offset of a fuel tank pressure transducer in sealed fuel systems of hybrid electric vehicles are inefficient, particularly for vehicles with limited engine run-time, as they can lead to undesired evaporative emissions and increased fuel efficiency loss, and are not suitable for autonomous or car-sharing models.
Innovation Solution
A method that wakes the vehicle controller when the fuel system is expected to be at atmospheric pressure, unseals the system, and determines the pressure sensor offset based on pressure changes, avoiding the release of fuel vapors and the use of onboard pumps.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the fuel tank is vented to atmosphere for a lengthy vehicle-off soak to test FTPT offset, then the FTPT offset can be determined, but fuel vapor trafficking to the fuel vapor canister occurs which is undesirable for vehicles with limited engine run-time
Solution Approach 1:
The system performs preliminary actions to prepare for FTPT offset testing by monitoring vehicle-off duration and determining when to wake the controller, ensuring the fuel tank is at atmospheric pressure before unsealing the system for offset determination
Solution Approach 2:
The fuel tank naturally returns to atmospheric pressure through temperature and pressure equalization during vehicle-off periods, eliminating the need for active venting or pumping systems to create the test conditions
2Measurement precision
If the engine is forced on to purge the fuel vapor canister, then the FTPT offset can be determined, but fuel efficiency of the vehicle is reduced
Solution Approach 1:
The system utilizes the natural atmospheric pressure conditions that occur during vehicle-off periods to perform FTPT offset testing, eliminating the need to run the engine for purging operations and thereby preserving fuel efficiency
Solution Approach 2:
The patent replaces the mechanical/engine-based purging system with a passive atmospheric pressure equalization process that occurs naturally during vehicle-off periods, eliminating the need for engine operation
3Measurement precision
If long vehicle-off soak times are used for FTPT offset determination, then offset can be accurately determined, but such vehicles may not regularly occur for autonomous or car-sharing models
Solution Approach 1:
The system continuously monitors vehicle-off duration and fuel tank pressure conditions, using feedback from these measurements to determine the optimal time to wake the controller and perform FTPT offset testing
Solution Approach 2:
The system dynamically adjusts the timing of FTPT offset determination based on real-time monitoring of vehicle-off duration and pressure conditions, rather than relying on fixed predetermined soak times
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 allows for accurate determination of the fuel tank pressure transducer offset without increasing evaporative emissions and reduces fuel efficiency losses, making it suitable for vehicles with limited engine run-time and various usage models.
Implementation Method 1
a fuel tank pressure transducer (FTPT) to measure the pressure or vacuum within the fuel system
Implementation Method 2
opportunities for using engine manifold vacuum to purge a fuel vapor storage canister
Implementation Method 3
engine-off natural vacuum (EONV) generated due to a change in temperature and pressure within the fuel tank following engine shutdown
Data Source
AI summary
Methods and systems are provided for determining an offset of a pressure sensor that is used for monitoring pressure in a fuel system that is sealed expect for refueling and other diagnostic events. In one example, a method includes waking a controller of a vehicle when it is expected that a pressure in a fuel system that is sealed from atmospheric pressure is at atmospheric pressure, unsealing the fuel system, and indicating an offset of the pressure sensor based on a pressure change after the fuel system is unsealed. In this way, pressure sensor offset may be determined regularly without undesirably loading a fuel vapor storage canister with vapors, which may be particularly advantageous for hybrid vehicles.