Fuel Tank Vent Valve Relief Openings Reduce Hysteresis
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Solution Overview
Problem
Vent valves for fuel tanks face challenges in preventing overfilling due to switching hysteresis, which allows additional fuel to enter the tank during refilling, especially when the pressure holding valve responds at 30 mbar, leading to a pressure rise and potential overfilling.
Innovation Solution
Incorporating relief openings in the valve element and guide to minimize pressure loss and reduce switching hysteresis, allowing for smaller component tolerances and reduced rattling noises, with optional second relief openings for pressure compensation and non-return functionality.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the pressure holding valve responds at 30 mbar to prevent overfilling, then overfill protection is improved, but switching hysteresis causes additional fuel to enter the tank during refilling
Solution Approach 1:
The patent modifies the pressure parameters by introducing relief openings that create a pressure differential across the valve element. The first relief opening at the lower end and second relief opening at the upper end establish different pressure zones, changing the pressure conditions under which the valve opens and closes, thereby reducing hysteresis and preventing overfilling.
Solution Approach 2:
The relief openings act as intermediary channels that mediate the pressure transmission between the valve housing and the external environment. By introducing these intermediate pressure relief paths, the system achieves more precise pressure control and reduces the switching hysteresis that causes overfilling.
2Reliability
If relief openings are incorporated to reduce switching hysteresis, then overfill protection is improved, but pressure loss during operation increases
Solution Approach 1:
The patent applies local quality by positioning relief openings at specific locations - the first relief opening at the lower end of the valve element and the second relief opening at the upper end. This localized placement ensures that pressure relief occurs only where necessary to reduce hysteresis, while maintaining pressure integrity in other critical areas of the vent valve system.
3Volume of moving object
If smaller compensating volumes are used to optimize installation space, then space utilization is improved, but overfill protection becomes more difficult to maintain
Solution Approach 1:
The patent changes the pressure parameters through the relief opening configuration, enabling the vent valve to maintain effective overfill protection even with reduced compensating volumes. The modified pressure differential created by the relief openings compensates for the smaller volume, allowing the valve to respond more precisely to pressure changes and prevent overfilling in compact tank designs.
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 reduces switching hysteresis, preventing overfilling by minimizing pressure loss and ensuring reliable venting system operation, even with smaller compensating volumes, and reduces rattling noises.
Implementation Method 1
closes the first connection by the force of gravity and/or by spring loading
Implementation Method 2
closes the first connection by the force of gravity and/or by spring loading
Implementation Method 3
relief openings in the valve element and guide to minimize pressure loss and reduce switching hysteresis
Data Source
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AI summary
Vent valve (1) for controlling the internal tank pressure of a fuel tank, having at least one valve housing (2) having at least one first connection (3) to the fuel tank and at least one second connection (4), which can be connected to a vent line leading to a fuel vapour filter, having at least one valve element (9), which is held in a valve seat (8) in a position in which it closes the first connection (3) by the force of gravity and/or by spring loading and, after a given pressure threshold is exceeded, is raised from the valve seat (8) and, when a given pressure threshold is undershot, returns to the initial position, wherein the valve element is arranged so that it can move within a valve element guide, the valve element has at least one first relief opening (10), which forms a bypass for a gap flow which arises during a return movement of the valve element characterized in that the valve element (9) has at least one second relief opening (14), which is closed by means of a nonreturn valve acting counter to the direction of closing of the vent valve (1) or which is open permanently in order to obtain forced leakage.