Fuel Vent Valve Liquid Trap Design
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Solution Overview
Problem
Fuel system venting issues in vehicles lead to slow fuel filling due to blockages in the vapour recovery system, often caused by liquid fuel entering the vent lines and clogging the charcoal canister, resulting in incomplete displacement of air and vapour, which prevents efficient refuelling.
Innovation Solution
A fuel system vent valve with a housing and movable float, incorporating a liquid trap and spring mechanism to prevent liquid fuel from entering the vent system, along with a cylindrical design and two-part float for pressure relief, ensuring the valve remains closed even when tilted, and optimized outlet positioning for efficient vapour release.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If the fuel vent valve is designed with a simple float mechanism, then the device complexity is reduced, but liquid fuel may enter the vent system causing canister clogging
Solution Approach 1:
The vent valve is divided into multiple functional components: a float mechanism for vapour venting control, a liquid trap for liquid fuel separation, and a canister isolation valve for vent line protection. This segmentation allows each component to perform its specific function effectively, preventing liquid fuel from reaching the canister while maintaining manageable complexity through modular design.
Solution Approach 2:
The liquid trap acts as an intermediary component between the fuel tank and the charcoal canister. It captures and retains liquid fuel that enters the vent system, preventing it from reaching and clogging the canister. This intermediary element protects the downstream component without requiring complete redesign of the entire venting system.
2Productivity
If the vent valve allows free vapour flow, then the refuelling speed is improved, but liquid fuel can escape during leak checks or purging operations
Solution Approach 1:
The vent valve employs dynamic control through a float mechanism that automatically adjusts the valve opening based on vapour pressure conditions. During refuelling, the float responds to pressure changes to maintain optimal vapour flow. During leak checks or purging, the system can tilt or pressurize, causing the float to position the valve to prevent liquid fuel escape while still allowing vapour management.
Solution Approach 2:
Different parts of the venting system have different functional requirements. The main vent valve is optimized for vapour flow during refuelling, while the liquid trap provides localized liquid fuel containment, and the canister isolation valve offers targeted protection during diagnostic operations. This local specialization allows each component to address specific operational conditions without compromising overall system performance.
3Reliability
If the liquid trap uses a large buffer volume, then liquid fuel containment is improved, but the device complexity and space requirement increase
Solution Approach 1:
The liquid trap is designed as a nested structure where the trap chamber is integrated within or adjacent to the existing vent valve housing. This nesting approach allows the liquid trap to utilize the space already allocated for venting components, minimizing additional space requirements while providing effective liquid fuel containment through the buffer volume.
4Reliability
If the vent valve is designed to remain closed during tilting, then liquid fuel prevention is improved, but vapour venting efficiency may be reduced
Solution Approach 1:
The float mechanism incorporates a counterbalancing design where the float's buoyancy force counteracts the effect of gravity during vehicle tilting. This ensures that the float maintains its position relative to the valve opening, keeping the valve closed when liquid fuel might escape during tilting operations, while still allowing vapour to pass through when pressure differential exists during normal refuelling.
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
The solution effectively minimizes liquid fuel entry into the vent system, allowing for smoother refuelling by creating a buffer volume and ensuring the valve remains closed, even under tilting conditions, thereby preventing clogging and enhancing fuel tank venting efficiency.
Implementation Method 1
a float (10) inside the housing (8), wherein the float (10) is movable between a first position in which the valve (7) is open and a second position in which the float (10) covers the opening (9) such that the valve (7) is closed
Implementation Method 2
The amount of liquid that leaks into the vent system under the above mentioned circumstances is not generally particularly high and by arranging a buffer volume above the valve seat the problem of getting liquid fuel in the vent system can be avoided for most cases
Data Source
AI summary
A fuel system vent valve comprises a housing with a first opening, and a float inside the housing. The float is movable between a first position in which the valve is open and a second position in which the float covers the first opening such that the valve is closed. The valve further comprises a liquid trap arranged above the housing such that it covers the first opening. The liquid trap comprises a housing in which is arranged a perimeter wall surrounding the first opening, the perimeter wall being arranged at a distance from the liquid trap housing thereby creating a first volume inside the wall and a second volume outside the wall. The first volume is larger than the second volume and the two volumes are connected via at least one gap between a top of the wall and a top of the liquid trap housing.