Fuel Tank Vapor Passage Blockage Detection
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Solution Overview
Problem
The existing diagnostic systems for evaporated fuel treatment systems face challenges in accurately determining vapor passage blockages due to the float valve's closing mechanism, which can lead to unreliable results, especially when the float valve is closing the opening, and errors in remaining fuel amount detection.
Innovation Solution
The diagnostic system includes a fuel tank, a canister, a vapor passage, a float valve, a remaining amount sensor, a pressure reducing mechanism, and a diagnostic device that executes specific processes to determine blockages by analyzing pressure changes and remaining fuel amounts, invalidating results when the float valve is likely closing the opening, and validating results when no blockage is present, ensuring accurate determination.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the float valve is used to shut off the vapor passage opening when liquid fuel level is high, then the fuel tank can be protected from overfilling, but the blockage detection accuracy deteriorates because the float valve closing state cannot be distinguished from an actual blockage
Solution Approach 1:
The diagnostic device continuously monitors the liquid level sensor output and uses this feedback to determine the operational state of the float valve. By comparing the detected liquid level with the float valve activation threshold, the system can distinguish between float valve closing and actual blockage conditions, resolving the measurement precision issue while maintaining fuel tank protection
Solution Approach 2:
The liquid level sensor acts as an intermediary element that provides information about the float valve state without directly interfering with the float valve mechanism. This intermediary measurement enables the diagnostic device to differentiate between float valve operation and vapor passage blockage, maintaining both fuel tank protection and detection accuracy
2Difficulty of detecting and measuring
If the diagnostic device executes blockage determination by reducing vapor passage pressure, then blockage detection capability is improved, but erroneous determination occurs when the float valve is closing the opening due to high liquid fuel levels
Solution Approach 1:
The diagnostic device performs a preliminary check of the liquid level sensor state before executing the blockage determination process. By verifying that the liquid level is below the float valve activation threshold beforehand, the system prevents erroneous determinations caused by float valve closing, while still maintaining the ability to detect actual blockages when conditions are appropriate
Solution Approach 2:
The diagnostic device dynamically adjusts its determination logic based on the liquid level condition. When the liquid level indicates the float valve may be closing, the device modifies its interpretation of pressure reduction results, invalidating blockage determinations that would otherwise be erroneous. This dynamic adaptation maintains determination accuracy across varying operational conditions
3Loss of time
If the determination process is executed when the ignition switch turns off, then diagnostic timing is improved, but the remaining fuel amount may change during the period before determination, leading to unreliable results
Solution Approach 1:
The system replaces physical observation of fuel level changes with electronic sensor monitoring. The liquid level sensor continuously provides electronic signals to the diagnostic device, enabling real-time tracking of fuel level without requiring physical measurement during the diagnostic period. This substitution maintains determination reliability while preserving timely execution
Solution Approach 2:
The liquid level sensor continuously monitors the fuel tank state automatically during the period between ignition switch-off and blockage determination. This self-monitoring service provides the diagnostic device with up-to-date information about fuel level changes, enabling the system to account for any fuel level variations that occur during the diagnostic window and maintain determination reliability
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 configuration enhances the reliability of blockage detection in the vapor passage by differentiating between blockages and the float valve's closing state, providing accurate results and preventing erroneous determinations, thus ensuring proper diagnosis of vapor passage conditions.
Implementation Method 1
The canister adsorbs evaporated fuel generated in the fuel tank to collect the evaporated fuel
Implementation Method 2
The pressure reducing mechanism is capable of reducing the pressure in the vapor passage
Data Source
AI summary
A diagnostic device is configured to execute a first acquisition process of acquiring a remaining amount of evaporated fuel in a fuel tank when an ignition switch turns off, as an end remaining amount, a determination process of, after the first acquisition process, determining whether there is a blockage of a vapor passage by reducing a pressure in a vapor passage with a pressure reducing pump when the end remaining amount is smaller than a prescribed value while the ignition switch is off, a second acquisition process of, after the determination process, acquiring a remaining amount of liquid fuel in the fuel tank when the ignition switch turns on, as a start remaining amount, and an invalidation process of invalidating a determination result that a blockage is present in the vapor passage in the determination process when the start remaining amount is larger than or equal to a set value.