Fuel Vapor Canister Load Inference via Recovery Line Pressure
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Solution Overview
Problem
Vehicle emission control systems fail to accurately determine fuel vapor canister load due to undiagnosed blockages in the vapor recovery line, leading to underestimated canister loading and increased bleed emissions, as blockages do not necessarily result in premature fuel dispenser shutoff and can be masked by fuel tank pressure fluctuations.
Innovation Solution
A method and system that monitor steady-state pressure in the vapor recovery line during refueling to infer fuel vapor canister load and adjust purging operations, using a vapor recovery line pressure sensor to diagnose restrictions and update canister purge schedules based on actual loading rates, ensuring accurate canister load determination and reduced emissions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the vapor recovery line is blocked, then the canister loading rate increases, but the blockage cannot be detected and canister load is underestimated
Solution Approach 1:
The system uses a pressure sensor to continuously monitor vapor recovery line pressure and compares it against expected pressure values. When the actual pressure deviates from expected pressure, the system detects the blockage and adjusts canister load determination accordingly, creating a feedback loop that maintains measurement accuracy despite system degradation
Solution Approach 2:
The pressure sensor acts as an intermediary element that indirectly detects blockage conditions by measuring pressure changes in the vapor recovery line. This intermediary measurement allows the system to infer blockage status without directly observing the blockage itself, enabling accurate canister load determination
2Device complexity
If fuel tank pressure is used to estimate canister loading rate, then estimation is simple, but accuracy decreases when vapor recovery line is degraded
Solution Approach 1:
The system incorporates pressure sensor feedback to continuously monitor vapor recovery line conditions and adjusts canister loading rate estimation based on actual pressure readings. This feedback mechanism maintains estimation accuracy even when the vapor recovery line becomes blocked, without requiring complex additional hardware
Solution Approach 2:
The system changes the measurement parameter from solely fuel tank pressure to vapor recovery line pressure, which provides more accurate information about actual vapor flow conditions. This parameter change enables accurate canister loading rate estimation while maintaining relatively simple system complexity
3Productivity
If the vapor recovery line circulates vapors, then canister loading rate is limited, but blockages go undiagnosed
Solution Approach 1:
The pressure sensor provides continuous feedback on vapor recovery line pressure during refueling operations. By comparing actual pressure against expected pressure values, the system can detect blockages while the vapor recovery line is actively circulating vapors, maintaining both refueling productivity and blockage detectability
Solution Approach 2:
The system uses the existing pressure sensor and control unit to perform self-diagnosis of the vapor recovery line. The control unit automatically compares measured pressure against expected values and detects blockages without requiring external diagnostic equipment, enabling the system to monitor its own functionality during normal operation
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 fuel vapor canister load post-refueling, adjusting purging operations to minimize bleed emissions by accounting for vapor recovery line degradation, thereby improving emission control and reducing the risk of failing emissions tests.
Implementation Method 1
monitor pressure in the vapor recovery line during a refueling event
Implementation Method 2
contains adsorbent material, such as activated carbon, capable of adsorbing hydrocarbon fuel vapor
Data Source
AI summary
A method is provided, comprising indicating a fuel vapor canister load based on a steady-state pressure in a vapor recovery line during a refueling event; and adjusting a canister purging operation in response to the indicated fuel vapor canister load. Restrictions in the vapor recovery line may increase the rate of fuel vapor canister loading during a refueling event. In this way, an accurate canister load may be determined following a refueling event, and canister purging operations adjusted accordingly.