Evaporated Fuel Leak Detection Using Pressure Differential
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Solution Overview
Problem
Existing evaporated fuel leak detecting systems are limited in their ability to efficiently detect leaks when the ignition switch is off, requiring electricity for a decompressing pump and a soak timer, and may result in incorrect detections due to unstable internal pressure in the fuel tank.
Innovation Solution
An evaporated fuel leak detecting apparatus that generates a pressure difference between the fuel tank and the atmosphere, using a decompressing pump, switch valve, pressure sensors, and a control unit to determine leak presence based on stable internal pressure conditions, eliminating the need for a soak timer and reducing power consumption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the ignition switch is turned off to conduct leak detection, then the detection can be performed when pressure is stable, but the number of detection opportunities is limited and additional components (soak timer, pump) are required
Solution Approach 1:
The system performs preliminary pressure stabilization by controlling the passage valve to isolate the fuel tank from the canister before conducting leak detection, ensuring stable pressure conditions without requiring the ignition switch to be off for an extended period
Solution Approach 2:
The system dynamically adjusts the detection process by monitoring pressure stability in real-time and proceeding with detection only when stability criteria are met, allowing flexible detection timing regardless of ignition switch state
2Measurement precision
If a pump is used to decompress the fuel tank for leak detection, then the detection can be conducted, but electricity is required and the system becomes more complex
Solution Approach 1:
The system utilizes the existing pressure differential that naturally occurs during normal vehicle operation (when the engine runs and creates vacuum in the intake manifold) to drive fuel vapor through the detection passage, eliminating the need for an external decompression pump
Solution Approach 2:
The passage valve serves multiple functions: it isolates the fuel tank from the canister for detection, controls pressure differential for vapor flow, and integrates with the existing evaporative emission control system without adding dedicated pump components
3Productivity
If leak detection is conducted when the ignition switch is on, then detection frequency increases, but incorrect detections may occur due to unstable internal pressure
Solution Approach 1:
The system continuously monitors fuel tank pressure and uses this feedback to determine whether pressure has stabilized before proceeding with leak detection, preventing false positives by ensuring stable baseline conditions
Solution Approach 2:
The system performs preliminary pressure stabilization by controlling the passage valve to isolate the fuel tank and allow pressure to equalize before conducting the actual leak detection measurement
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
Enables frequent and accurate leak detection without turning off the ignition switch, reducing power consumption and avoiding incorrect detections by ensuring internal pressure stability before conducting the detection process.
Implementation Method 1
an evaporated fuel leak detecting apparatus that detects a leak of fuel evaporated from a fuel tank by generating a pressure difference between an inside and an outside of the fuel tank
Implementation Method 2
The pressure controlling portion is disposed in the detection passage, and compresses or decompresses inside of the fuel tank
Data Source
AI summary
A first determiner determines whether a pressure in a fuel tank is within a predetermined range when an ignition switch of an engine is on. A second determiner determines whether a valve allows or prohibits a communication between the fuel tank and a switch valve, when the first determiner determines that the pressure in the fuel tank is within the predetermined range. A control unit controls a pressure controlling portion based on a determination result of the first determiner and a determination result of the second determiner. A leak determiner determines whether the fuel tank has a leak of evaporated fuel based on a signal output from a first detector detecting a pressure in a detection passage and a signal output from a second detector detecting a pressure in the fuel tank.