Reversible Purge Pump Leak Detection in Vehicle Emission Systems
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Solution Overview
Problem
Current evaporative emission control systems for vehicles lack an effective method to detect leaks, which can lead to fuel vapors escaping into the atmosphere, affecting engine performance and emissions.
Innovation Solution
A system comprising a reversible purge pump connected between a fuel tank and an engine, along with a purge control valve, operates in both directions to supply fuel vapor and air, allowing for a leak detection method by pressurizing the system and comparing initial and test pressures to determine the presence of a leak.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a traditional evaporative emission control system is used, then fuel vapors are contained, but leak detection capability is insufficient
Solution Approach 1:
The purge pump is designed to perform multiple functions: it operates in a forward direction to supply fuel vapor from the fuel tank to the engine during normal operation, and in a reverse direction to supply air to the fuel tank for leak detection. This multi-functionality eliminates the need for a separate air supply device, improving reliability while avoiding increased system complexity
Solution Approach 2:
The system uses its own purge pump to perform leak detection by reversing its operation direction, rather than requiring an external diagnostic device. The pump's inherent bidirectional capability allows the system to self-diagnose leaks, improving detection capability without adding external complexity
2Measurement precision
If a reversible purge pump is used for leak detection, then accurate leak detection is enabled, but pump complexity increases
Solution Approach 1:
The purge pump is designed as a reversible pump that can operate in two directions: forward direction for vapor evacuation and reverse direction for air supply during leak detection. This single device performs both normal operation and diagnostic functions, achieving accurate pressure measurement for leak detection without requiring additional specialized equipment
Solution Approach 2:
The system achieves accurate leak detection by monitoring pressure changes in the fuel tank during the leak detection cycle. The reversible pump introduces air to increase pressure, and pressure sensors detect the pressure differential to determine leaks, utilizing parameter changes rather than complex mechanical detection mechanisms
3Reliability
If the purge pump operates in reverse direction, then air is supplied to the fuel tank for leak detection, but fuel vapor supply to engine is interrupted
Solution Approach 1:
The leak detection operation is performed periodically as a separate diagnostic cycle rather than continuously during normal operation. The control unit activates the reversible pump in reverse direction only during scheduled leak detection cycles, while maintaining normal forward operation for vapor supply during other times, thus achieving both detection accuracy and operational continuity
Solution Approach 2:
The system performs leak detection at predetermined intervals or under specific conditions (such as when the engine is off or during idle periods), preparing the system for accurate detection without interfering with continuous vapor supply during active engine operation. The timing is planned in advance to minimize impact on productivity
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 solution enables accurate detection of leaks in the evaporative emission control system, ensuring that fuel vapors are not lost to the atmosphere, thereby improving engine efficiency and reducing emissions by identifying and indicating leaks based on pressure differences.
Implementation Method 1
A test pressure of the evaporative emission control system is detected after closing the purge control valve and stopping operation of the reversible purge pump. A presence of a leak in the evaporative emission control system is determined when the test pressure differs from the expected system pressure based on the initial pressure
Data Source
AI summary
An evaporative emission control system for a vehicle includes an engine, a fuel tank connected to the engine and a reversible purge pump connected between the fuel tank and the engine. Fuel vapor generated in the fuel tank is supplied to the engine. The purge pump is operable in a first direction to supply the fuel vapor from the fuel tank to the engine and a second direction to supply air to the fuel tank. A purge control valve is connected between the reversible purge pump and the engine to control a flow of the fuel vapor to the engine.