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PASSIVE PURGE EVAP METHOD FOR VEHICLES WITH DUAL FUEL TANKS

IP.com Disclosure Number: IPCOM000242929D
Publication Date: 2015-Aug-31
Document File: 1 page(s) / 226K

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The IP.com Prior Art Database

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PASSIVE PURGE EVAP METHOD FOR VEHICLES WITH DUAL FUEL TANKS

Vehicles sold in North American market contain a carbon canister that adsorbs refueling, diurnal and running loss vapors. Engine running manifold vacuum is used to desorb the vapor from the activated carbon canister via opening of Canister Purge Valve. Desorbed vapors are combusted in engine. This is commonly known as "purging". Canisters contain wood based activated carbon pellets. The pellets are porous and fuel vapor sticks to them. When air flows across carbon pellets, the hydrocarbons (HC) are purged out. Boosted vehicles have problems with purge efficiency. During boost, there is insufficient vacuum to adequately purge the canister. Vehicles must demonstrate that the canister is cleaned of HC on any of the EPA drive cycles. Failure to clean the canister results in lack of certification. If vehicles fail the 2 or 3 day diurnal test, an extra bleed canister is installed in series with the main canister. This adds cost to the system and adds resistance to the Evap system resulting in interference with refueling effort.

Method

Some vehicles, such as All Wheel Drives or Heavy Duty trucks, have dual fuel tanks. This method performs passive purge actively in vehicles with dual tanks. During the key off state, the method determines whether the current time of day is the sunlight hours or night hours. This is inferred from onboard real time clock. During the night hours, natural cooling develops inside the...