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Method to reduce fuel volatility in PHEV vehicles to improve Evap monitor robustness and emissions

IP.com Disclosure Number: IPCOM000238130D
Publication Date: 2014-Aug-04
Document File: 1 page(s) / 242K

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The IP.com Prior Art Database

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Method to reduce fuel volatility in PHEV vehicles to improve Evap monitor robustness and emissions

Vehicles sold in North America must adsorb fuel vapors in a carbon canister and purge the vapors when engine is combusting. Vehicles sold in North America are also required to perform Evap leak detection. Green states required to monitor for 0.02" leaks. For HEV, engine run time is limited hence a vacuum pump is required for leak detection. One such vacuum pump is the ELCM made by Denso Corporation. In PHEV, engine run time is limited and hence fuel consumption is also limited if the operator chooses to charge the battery frequently. As a result, winter fuel which has a high RVP value, can linger into the summer months. High RVP fuel can cause robustness issues with the Evap leak monitor as fuel vapors generate pressure which counteracts the vacuum pull generated by the ELCM pump. A method to weather winter fuel to summer fuel levels is desired for OBD monitors.

Method

The method weathers fuel by purging on the fuel tank vapor dome instead of the canister. Method relies on a capless refueling unit as an enabler. First, the fresh air line is closed by activating ELCM COV valve.

If system is not equipped with ELCM pump, the CVS is commanded closed. Second, the FTIV valve is commanded open. Last, engine vacuum is used to evacuate the gas tank vapor dome until the capless unit is forced open (at -20 InH2O).Note that PHEV fuel tanks are made of steel and designed to wi...