Evaporation Leak Check Using Pump Characteristic Reference
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Solution Overview
Problem
Existing evaporation leak check systems face inaccuracies due to clogging of reference orifices by foreign objects, leading to unreliable detection of fuel tank leaks, and require complex setups with additional components like filters.
Innovation Solution
An evaporation leak check system that uses a pump and a switching portion to create pressure differences within the fuel tank, eliminating the need for a reference orifice by calculating a reference pressure based on closed-state and open-time pressures, allowing for precise leak detection without actual fluid flow through an orifice.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If air is drawn from outside to flow through a reference orifice, then the reference pressure can be established, but foreign objects clog the reference orifice causing measurement inaccuracy
Solution Approach 1:
The patent extracts the harmful element (reference orifice) from the system. Instead of using a physical reference orifice that can be clogged, the invention calculates the reference pressure theoretically based on pump characteristics and flow rate characteristics, eliminating the clogging problem while maintaining measurement accuracy
Solution Approach 2:
The patent creates a virtual copy of the reference pressure measurement process. Rather than physically measuring pressure through a reference orifice, the system calculates what the reference pressure should be based on pump performance characteristics, providing an accurate reference without the physical limitations of an actual orifice
2Reliability
If a filter is arranged upstream of the reference orifice to collect foreign objects, then the reference orifice is protected from clogging, but the number of components increases and system construction becomes complicated
Solution Approach 1:
The patent removes both the reference orifice and the required filter from the system. By calculating reference pressure theoretically from pump characteristics, the invention eliminates the need for physical components that would require protection, thereby reducing system complexity while maintaining reliability
Solution Approach 2:
The system uses the pump's own performance characteristics to generate the reference pressure value. The pump characteristics expression and flow rate characteristics expression work together to calculate the reference pressure without requiring external filters or protective components, making the system self-sufficient and simpler
3Measurement precision
If the diameter of the reference orifice is made smaller to improve leak detection sensitivity, then minute leaks can be detected, but the orifice is more easily clogged by foreign objects
Solution Approach 1:
The patent creates a virtual reference pressure calculation that mimics the effect of a small reference orifice without the physical limitations. By calculating reference pressure from pump characteristics, the system achieves the sensitivity of a small orifice while avoiding its vulnerability to clogging
Solution Approach 2:
The invention extracts the functional benefit of a small reference orifice (sensitive leak detection) while removing its harmful aspect (clogging susceptibility). The theoretical calculation provides the same detection capability without the physical constriction that attracts and traps foreign objects
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 high-precision evaporation leak detection, reduces system complexity, and maintains accuracy over time, while preventing fuel evaporation from escaping through minute gaps in the fuel tank.
Implementation Method 1
an adsorbent arranged in the first passage; The adsorbent adsorbs evaporation fuel generated in the fuel tank
Implementation Method 2
a pump; a fuel tank having fuel evaporation leak that is checked by forming a pressure difference between inside and outside of the fuel tank
Data Source
AI summary
A pump characteristics expression of a pump is developed based on a closed-state pressure detected when the pump is driven while a space between a pump passage and a first passage is closed, an open-time pressure detected immediately after the space is opened while the pump is operated, and a flow rate characteristics expression of the pump passage. A reference pressure is determined by an intersection point between the pump characteristics expression of the pump and a flow rate characteristics expression of an orifice having a predetermined passage area. A leak check portion determines whether a leak of fuel evaporation generated from a fuel tank is within an allowable range by comparing the reference pressure and a pressure detected when the pump is operated for a predetermined period while the space is opened.