Evaporative Fuel Processing Device Leak and Pump Diagnosis
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Solution Overview
Problem
Conventional evaporative fuel processing devices face challenges in accurately determining leakage in evaporation piping systems and diagnosing pump abnormalities, often leading to faulty determinations and increased repair time.
Innovation Solution
The device employs a pump and pressure sensor to alter internal system pressure relative to atmospheric pressure, with an abnormality determiner using threshold values to differentiate between leaks and pump issues based on pressure changes, preventing faulty determinations by adjusting threshold values according to system pressure.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a pump and pressure sensor are used to pressurize the system for leakage determination, then leakage detection capability is improved, but the ability to accurately diagnose pump abnormalities deteriorates due to false positives
Solution Approach 1:
The patent divides the diagnosis process into two distinct phases: a leakage determination phase where the pump operates and pressure changes are monitored, and a pump abnormality determination phase where the pump is stopped and pressure changes are monitored again. This segmentation allows each phase to focus on its specific diagnostic target without interference from the other, resolving the contradiction between leakage detection accuracy and pump abnormality diagnosis reliability.
Solution Approach 2:
The patent performs leakage determination as a preliminary action before pump abnormality determination. By first establishing whether a leak exists in the evaporation piping system, the system can then attribute pressure changes during the second phase solely to pump performance issues, eliminating false positives and improving diagnostic reliability.
2Measurement precision
If the pump operates to pressurize the system for leakage determination, then leakage detection is enabled, but false abnormality determinations occur due to pressure changes caused by pump operation
Solution Approach 1:
The patent segments the diagnostic process into two distinct time periods: first, the pump operates to enable leakage detection through pressure changes; second, the pump is stopped to obtain accurate pump status information through pressure changes. This temporal segmentation ensures that pressure changes in each phase are attributable to the intended cause only, eliminating information loss and false determinations.
Solution Approach 2:
The patent employs periodic action by alternating between pump operation and pump stop states at specific intervals during the diagnosis process. This periodic switching allows the system to collect data under different conditions (pump running vs. pump stopped) and analyze pressure changes accordingly, preventing false information loss while maintaining accurate leakage detection.
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 approach enables precise leak and pump abnormality determination, reducing repair time and preventing incorrect diagnoses, thus improving diagnostic accuracy and efficiency.
Implementation Method 1
The pump operates so as to pressurize or depressurize an internal pressure or an in-system pressure, which is the internal pressure of the evaporation piping system, bringing it to a positive pressure or a negative pressure with respect to the atmospheric pressure
Implementation Method 2
The pressure sensor detects a pressure inside the system (i.e., detects the in-system pressure)
Data Source
AI summary
An evaporative fuel processing device for determining a leak of an evaporation piping system also determined pump abnormality by including a pump, a pressure sensor and an abnormality determiner, i.e., by pressuring/de-pressuring the system to a positive/negative value against an atmospheric pressure for leak determination, by detecting a pressure of the system, and by determining a leak hole in a normal leak determination mode based on an absolute value of the detected pressure reaching or not reaching a target value after pump operation and based on an assumption that the pump is normal. Specifically, after lapse of a determination time from a pump stop, the absolute value equal to or less than a normal leak determination threshold value is determined that a leak hole is present in the system. Further, the absolute value not reaching the target value even after pump operation triggers a pump abnormality determination mode.