Cooling Fan Assisted Engine-Off Vacuum Test
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
The engine-off natural vacuum (EONV) leak test in vehicle emission control systems is prone to false failures due to ambient temperature conditions, particularly during mild weather, which can lead to unnecessary engine service and warranty claims.
Innovation Solution
Operating a cooling fan during an engine-off condition at mild ambient temperatures to increase the fuel tank vacuum and using a control system to monitor and seal the fuel system, allowing the fuel tank pressure to equilibrate, and activating the cooling fan to assist in vacuum development for leak identification.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the EONV test is run during mild ambient temperatures without additional cooling, then the test duration can be kept within battery charge limits, but the fuel tank vacuum may not reach expected threshold levels resulting in false failures
Solution Approach 1:
The patent changes the thermal parameters of the fuel tank by activating the cooling fan to artificially create a temperature differential between the fuel tank and ambient air. This accelerates the cooling rate and vacuum development, allowing the test to reach threshold levels within the allotted battery charge time while maintaining accurate leak detection capability.
Solution Approach 2:
The cooling fan is activated before the vacuum threshold needs to be reached, preemptively creating the necessary temperature differential and accelerating vacuum development. This preliminary cooling action ensures that even during mild ambient temperatures, the fuel tank will reach the required vacuum threshold within the test duration constraints.
2Loss of time
If the cooling fan is activated to accelerate vacuum development, then the EONV test can be completed within battery charge limits, but additional energy is consumed by the cooling fan
Solution Approach 1:
The cooling fan is activated only partially - specifically during the EONV test window when mild ambient temperatures would otherwise prevent adequate vacuum development. The fan operates at excessive capacity relative to natural cooling needs, but only for the limited duration of the test, consuming energy strategically to achieve the vacuum threshold within battery charge constraints rather than relying on slow natural cooling.
Solution Approach 2:
The cooling fan is activated periodically only during the EONV test duration rather than continuously. This periodic activation aligns energy consumption with the specific time window when vacuum development is needed, allowing the test to complete within battery charge limits while minimizing overall energy usage compared to continuous fan operation.
3Reliability
If the EONV test duration is extended to allow adequate vacuum development during mild temperatures, then more accurate leak detection is achieved, but the battery charge may be depleted preventing vehicle restart
Solution Approach 1:
The patent changes the thermal cooling parameter by activating the cooling fan, which accelerates vacuum development rate. This allows the test to reach the vacuum threshold in a shorter time period, thereby completing the accurate leak detection before the battery charge is depleted, preventing vehicle restart issues.
Solution Approach 2:
The cooling fan is activated preliminarily during the test to create the necessary temperature differential early in the test window. This preliminary cooling action ensures rapid vacuum development, allowing the complete leak detection process to finish within the battery charge availability window, preventing depletion that would prevent vehicle restart.
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 method enhances the robustness of the EONV test, reducing false failures and ensuring accurate leak detection, thereby minimizing unnecessary vehicle service and warranty claims.
Implementation Method 1
operating a cooling fan to increase a fuel tank vacuum
Implementation Method 2
as fuel vapors condense to liquid fuel. Vacuum generation is monitored
Data Source
AI summary
A method for a vehicle fuel system, comprising: during an engine-off condition, including an ambient temperature within a threshold range, operating a cooling fan to increase a fuel tank vacuum; and indicating leaks in the vehicle fuel system based on the increased vacuum. In this way, an EONV test may be run at mild ambient temperatures which would not otherwise result in the development of adequate fuel tank vacuum to pass the EONV test.