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In Situ FTPT Rationality in NIRCOS Sealed Fuel Tanks Utilizing ELCM Evap Leak Detection Pump

IP.com Disclosure Number: IPCOM000249220D
Publication Date: 2017-Feb-10
Document File: 1 page(s) / 199K

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The IP.com Prior Art Database

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In Situ FTPT Rationality in NIRCOS Sealed Fuel Tanks Utilizing ELCM Evap Leak Detection Pump

Plug-in Hybrid Electric Vehicles (PHEV) utilize sealed tanks made of steel designed to withstand pressures and vacuums that result from diurnal temperature cycle. Tanks are sealed via a Fuel Tank Isolation Valve (FTIV). Onboard Diagnostic (OBD) regulations mandate that the Evaporative emissions (Evap) system be checked for leaks. Current Evap leak detection monitor uses an Evap Leak Check Monitor (“ELCM”) pump to evacuate the canister side of the system every time the monitor runs. If the tank side of the system is holding pressure or vacuum, the inference is that the tank is leak free and ELCM does not evacuate the tank side. CARB expressed concern that the HPFTPT (High Pressure Fuel Tank Pressure Transducer) can fail in range. In that case, a leaky tank will go undetected since the Evap monitor will not evacuate the tank side to perform a leak detection check - hence hydrocarbons would be emitted into the atmosphere. Furthermore, during refueling, the PHEV refuel door is not opened up until the system has been depressurized. If the sensor fails in range, the tank will depressurize but FTPT will falsely indicate pressure or vacuum and the operator will have to use the manual override in the trunk to open the fuel door. A rationality test on the FTPT is desirable. Prior art methods have solved the rationality problem by opening the FTIV, turning on the ELCM pump and correlating the responses and the rate of changes of the FTPT and the ELCM pressure sensors. Venting the fuel tank to perform the diagnostic has drawbacks in that the canister is loaded, the fuel tank is fatigued and electrical power is utilized to energize the FTIV. Hence, a method that rationalizes the FTPT in situ without venting (opening FTIV) the NIRCOS (Non- Integrated Refueling Canister Only System) fuel tank is desirable in accordance with the above issues. Method

This method opportunistically performs a diagnostic on the NIRCOS FTPT when an altitude change is encountered during the drive cycle. The EL...