Method to Adsorb Crankcase Blow-by Gas Hydrocarbons into Evap Canister during Engine Non-Combusting Modes
Publication Date: 2014-Aug-08
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Method to Adsorb Crankcase Blow-by Gas Hydrocarbons into Evap Canister during Engine Non- Combusting Modes
Vehicles sold in North America must adsorb fuel vapors in a carbon canister and purge the vapors when engine is combusting. Engine crankcase is a source of hydrocarbon (HC) emissions into the atmosphere. The PCV valve is the first emission component introduced in the engine back in 1960s. The blow-by gases from the crankcase are typically fed back into the intake manifold. These blow-by gases contain hydrocarbons that did not combust and leaked through the piston rings. By introducing these HC back into the intake manifold, the intent is that the HC will be combusted once they enter the cylinders. There are certain vehicle modes in which pistons move up and down without combusting. Hence, blow- by gases still occur but they circulate through the engine without combusting. These vehicle modes include: Decel Fuel Shut Off (DFSO) mode, Variable displacement engine mode (cut off certain number of cylinders to conserve fuel), misfiring cylinder mode, and catalyst protection mode. If the blow-by gases are not combusted and vehicle is turned off, HC Evap emissions will increase.
The method aims at re-routing crankcase blow-by HC gases into the existing Evap refueling canister during non-combusting engine modes where the HC are adsorbed. When engine is combusting once again, the HC are purged from the canister and into the cylinders. Strategy energizes a new...