Closed Tank Fuel System Shut-Off Valve Control
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Solution Overview
Problem
In closed tank systems for vehicles, there is a risk of fuel in liquid form reaching the canister through the shut-off valve during supplemental refueling, causing differential pressure and fuel suction from the tank, especially when the fuel level exceeds the full tank liquid level.
Innovation Solution
A closed tank system that includes a fuel tank, a canister connected via a communication passage, a fill-up limiting valve, a shut-off valve, and a fuel remaining amount detector, where a hardware processor inhibits the opening of the shut-off valve when the engine is in operation and the fuel remaining amount exceeds a predetermined threshold, preventing fuel from reaching the canister.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the shut-off valve is opened during supplemental refueling when fuel level exceeds full tank liquid level, then fuel can be supplied to the engine, but fuel in liquid form reaches the canister through the shut-off valve causing differential pressure and fuel suction from the tank
Solution Approach 1:
The control section checks the fuel level against the threshold (over-full tank liquid level) before allowing the shut-off valve to open. This preliminary check prevents the valve from opening when fuel level is too high, avoiding the harmful effect of liquid fuel reaching the canister while still allowing normal operation when fuel level is appropriate
Solution Approach 2:
The system continuously monitors fuel level and uses this feedback to control the shut-off valve state. When fuel level exceeds the threshold, the control section receives feedback and automatically closes the shut-off valve, creating a closed-loop control system that prevents liquid fuel from reaching the canister
2Reliability
If the fill-up limiting valve is used to close the communication passage when fuel level reaches full tank liquid level, then overfilling is prevented, but supplemental refueling cannot be performed when fuel level exceeds this level
Solution Approach 1:
The system introduces a second threshold (over-full tank liquid level) that is higher than the full tank liquid level. This parameter change allows the system to distinguish between normal full tank conditions (where refueling should stop) and supplemental refueling conditions (where refueling can continue with shut-off valve closed), providing both overfill protection and supplemental refueling capability
Solution Approach 2:
The control section acts as an intermediary between the fill-up limiting valve and the shut-off valve. It receives signals from the fuel level detector and coordinates both valves appropriately: the fill-up limiting valve handles normal overfill prevention, while the control section manages the shut-off valve to enable supplemental refueling when needed
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
Prevents fuel in liquid form from reaching the canister through the shut-off valve, ensuring effective control and reducing the risk of fuel loss during engine operation and supplemental refueling.
Implementation Method 1
adapted to operate to close the communication passage by allowing a float to float on the fuel when a fuel level reaches a predetermined full tank liquid level
Implementation Method 2
a canister that is connected via a communication passage to the fuel tank and adapted to adsorb evaporative fuel generated in the fuel tank
Data Source
AI summary
A closed tank system includes: a fuel tank; a canister adapted to adsorb evaporative fuel generated in the fuel tank; a fill-up limiting valve provided inside the fuel tank so as to be communicated with the evaporative fuel discharge passage and adapted to operate to close the evaporative fuel discharge passage when a fuel level reaches a predetermined full tank liquid level; a shut-off valve adapted to operate to open or close the evaporative fuel discharge passage; a fuel remaining amount sensor adapted to detect a remaining amount of fuel; and a hardware processor that causes a control section to carry out control for allowing the shut-off valve to be opened or closed. The hardware processor causes the control section to inhibit the control for allowing the shut-off valve to be opened when an engine is in operation and the detected remaining amount of fuel exceeds a predetermined threshold.