Fuel Tank Vent Valve Delayed Float Response
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Solution Overview
Problem
Existing vent control valves for fuel tanks face challenges in ensuring proper venting of fuel vapor while preventing overfilling, especially when the vertical dimension is small, as they struggle to balance the flow rate of vapor and the sensitivity to liquid fuel level changes.
Innovation Solution
A vent control valve design featuring a cylindrical housing with a float assembly and a communication hole that allows delayed liquid fuel level drop after filling, enabling controlled venting by adjusting the size and number of communication holes and rib configurations to manage float movement and pressure changes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the opening area of the small opening in the housing is reduced to delay the dropping of liquid fuel level, then overfilling prevention is improved, but fuel vapor venting flow rate deteriorates
Solution Approach 1:
The communication path for fuel vapor is segmented into two parts: a small opening for controlled delayed communication and a skirt passage for additional vapor flow path. This segmentation allows the small opening to maintain its delay function while the skirt provides an alternative path that maintains venting efficiency.
Solution Approach 2:
The invention adds a vertical dimension by extending the housing downward to form a skirt that reaches into the fuel tank. This creates a new spatial dimension for vapor communication that is independent of the small opening's flow rate limitations.
2Length of moving object
If the height of the housing is reduced to minimize vertical dimension, then space utilization is improved, but the sensitivity and effectiveness of the float valve mechanism deteriorates
Solution Approach 1:
The housing is extended vertically downward to form a skirt that reaches into the fuel tank, utilizing the vertical dimension differently. This extended skirt portion provides the necessary float movement space and liquid fuel level sensing capability without increasing the overall height of the main housing body.
Solution Approach 2:
The float valve mechanism is nested within the extended skirt portion of the housing, which itself is nested within the fuel tank's liquid fuel. This nested arrangement allows the float valve to function effectively within the available vertical space by positioning it at the appropriate depth within the fuel tank.
3Productivity
If the opening area of the small opening is made large to ensure adequate vapor flow rate, then fuel vapor venting is improved, but the liquid fuel level drops too quickly causing premature float valve closing
Solution Approach 1:
The communication path is segmented into a small opening for delayed communication and a skirt passage for additional vapor flow. This allows the system to accommodate larger effective opening areas through the skirt while maintaining the delay function of the small opening.
Solution Approach 2:
The skirt acts as an intermediary structure that provides a controlled passage for fuel vapor between the tank interior and the canister. It mediates between the conflicting requirements by providing a flow path that maintains pressure differential longer than a direct large opening would.
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 design effectively delays the liquid fuel level drop to prevent overfilling and ensures proper venting of fuel vapor, maintaining adequate flow rates even with a reduced vertical dimension, thus addressing the dual challenges of vapor venting and overfill prevention.
Implementation Method 1
a float assembly received in the housing and guided for a vertical movement therein
Implementation Method 2
the fuel vapor is gradually introduced into the housing via the small opening, and this causes the pressure in the housing to drop
Data Source
AI summary
In a vent control valve for a fuel tank, a housing receiving a float assembly therein is provided with a communication hole passed across a wall of the housing, and an opening of the communication hole facing an interior of the housing is directly exposed to an interior of the housing when the float assembly is in a low position and overlaps with a peripheral wall of the float assembly when the float assembly is in a high position. By suitably selecting the size of the communication hole and/or the number thereof, a desired delay in the dropping of the liquid fuel level in the housing following the filling up of the fuel tank can be achieved. Thereby, overfilling of the fuel tank can be avoided.