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EONV METHOD USING SINGLE THERMOCOUPLE FOR ENABLEMENT AND DIAGNOSTICS

IP.com Disclosure Number: IPCOM000241757D
Publication Date: 2015-May-28
Document File: 1 page(s) / 250K

Publishing Venue

The IP.com Prior Art Database

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EONV METHOD USING SINGLE THERMOCOUPLE FOR ENABLEMENT AND DIAGNOSTICS

Vehicles sold in North America are required to perform Evap leak detection as part of OBDII requirements. Green states required to monitor for 0.02" leaks as part of the Clean Air Act Section 177. (CAA) IN MY2017, all states have to perform 0.02" leak tests.For regular gasoline engines, a technique called Engine Off Natural Vacuum (EONV) is used to perform leak detection. EONV relies on heat rejection from the hot engine to reach the tank and warm the bulk fuel during driving.At key off, if the drive cycle resulted in adequate heat rejection into the liquid fuel, the PCM stays alive and seals the Evap system by closing the CVS. The FTPT pressure sensor is used to monitor the Evap system pressure or vacuum for leak integrity. Heat rejection is inferred by miles driven or total air mass inhaled by the engine. Both these heat rejection inferences have shortcomings which results to EONV executing when it shouldn't. Ultimately, the temperature of the liquid fuel is the best measure that indicates robust heat rejection.

Method

This method infers heat rejection into the liquid fuel from actual fuel liquid temperature measurement, as opposed to inferring it from distance travelled, AM summation, etc. ElectroActive Polymer material (EAP) is mounted at end of the fuel level float. A thermocouple (T/C) is attached to the EAP material. The EAP material deflects upward when energized with voltage. Additio...