Evaporative Emissions Leak Detection Using Variable-Speed Pump Control
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Solution Overview
Problem
Existing leak detection methods for evaporative emissions systems in gasoline powered vehicles are inefficient and inaccurate due to the effects of entropy, particularly at high ambient temperatures, leading to excessive venting of gasoline vapors and difficulty in achieving precise pressure control.
Innovation Solution
A method using a variable speed pump to dynamically adjust pressure by alternating between different speeds to reach target pressures, mitigating the effects of entropy and ensuring accurate leak detection by monitoring and correcting pressure deviations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a constant speed pump is used to create vacuum or pressurize the system, then the system can be sealed and pressure can be monitored to detect leaks, but the effects of entropy make it difficult to perform the test quickly and accurately
Solution Approach 1:
The patent applies a variable speed pump instead of a constant speed pump, allowing the pump speed to be dynamically adjusted during the leak test. The controller varies the pump speed to different levels (e.g., first speed, second speed, third speed) at different stages of the test to optimize both the speed of pressure achievement and the accuracy of leak detection, thereby resolving the contradiction between test duration and detection accuracy
Solution Approach 2:
The patent changes the operating parameters of the pump by varying its speed at different stages of the leak test. The controller adjusts the pump speed parameter to achieve target pressure levels more quickly while maintaining detection accuracy. This parameter variation allows the system to overcome entropy effects and complete the test faster without sacrificing precision
2Manufacturing precision
If the pump operates at a fixed set speed, then the system structure is simple, but the pressure control precision deteriorates due to entropy effects at high ambient temperatures
Solution Approach 1:
The patent implements a dynamic pump speed control system that adjusts the pump operating speed based on real-time pressure feedback and test stage requirements. The controller varies the pump speed to maintain precise pressure control throughout the test, especially at high ambient temperatures where entropy effects are most pronounced. This dynamic adjustment improves pressure control precision while the added control complexity is managed through automated feedback mechanisms
3Productivity
If the pump speed is increased to reach target pressure faster, then the test time is reduced, but the pressure control accuracy decreases due to entropy effects
Solution Approach 1:
The patent employs periodic variation of pump speed during the leak test. The controller cycles the pump through different speed levels (first speed to reach initial target pressure, then second speed for intermediate pressure, and third speed for final pressure) at different stages. This periodic speed variation allows the system to achieve target pressure quickly while maintaining accuracy by adjusting speed based on real-time pressure feedback and test progression
Solution Approach 2:
The patent implements a feedback control mechanism where the controller continuously monitors actual pressure and compares it to target pressure values. Based on this feedback, the controller adjusts pump speed to correct any deviations, ensuring both fast pressure achievement and high measurement accuracy. The feedback loop allows the system to compensate for entropy effects and maintain precision even at high test speeds
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 method enables rapid and precise leak detection by minimizing the impact of entropy, reducing the time required to achieve target pressures, and accurately identifying leaks, thereby complying with regulatory limits.
Implementation Method 1
A variable speed pump is used to create or maintain a pressure differential in the system
Implementation Method 2
A pressure transducer is used to monitor pressure changes in the system
Data Source
AI summary
A method of detecting a leak in an evaporative emissions system includes sealing a system, operating a variable speed pump at a first speed to reach a first target pressure in the system, monitoring an actual pressure in the system, determining whether an error between the actual pressure and the first target pressure exceeds a threshold, and operating the variable speed pump at a second speed different than the first speed when the error exceeds the threshold to reach a second target pressure different than the first target pressure.