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UTILIZING OXYGEN SENSOR INSIDE PHEV FUEL TANK TO IMPROVE EVAP MONITOR ROBUSTNESS

IP.com Disclosure Number: IPCOM000232439D
Publication Date: 2013-Nov-08
Document File: 1 page(s) / 244K

Publishing Venue

The IP.com Prior Art Database

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UTILIZING OXYGEN SENSOR INSIDE PHEV FUEL TANK TO IMPROVE EVAP MONITOR ROBUSTNESS

PHEV vehicles typically contain sealed fuel tanks due to limited engine run time. The fuel tank is referred to as NIRCOS (Non Integrated Refueling Only Canister). OBD II regulations dictate that the entire Evap system including the fuel tank be monitored for 0.02" leaks. Future emission for the fuel tank side of the Evap system be monitored for 0.01" leak. The common method to perform leak detection is by use of a vacuum pump with the ELCM system being the industry standard. The ELCM has a built in 0.02" reference orifice that helps with mitigating noise factors such as temperature, barometric pressure, humidity, etc… Two noise factors that the ELCM does not compensate for are fuel volatility and a delta temperature between the tank and the surrounding environment. High RVP fuel and heat transfer into the fuel tank can cause false failures with ELCM monitor.

Method

The method being proposed is to install an oxygen sensor inside the tank to distinguish between a true leak inside the fuel tank versus high RVP fuel or heat transfer effects. As the ELCM attempts to evacuate the fuel tank to a target vacuum level to assess leak integrity, high RVP fuel and/or heat transfer will counteract the vacuum pump. This can result in monitor robustness issues. To properly distinguish real leaks from unwanted system interaction noise, the idea is to install an oxygen sensor similar to the one use...