CRANK EVENT HYDROCARBON ADSORPTION INTO EVAP CANISTER FOR HEV’S
Publication Date: 2014-Oct-13
The IP.com Prior Art Database
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CRANK EVENT HYDROCARBON ADSORPTION INTO EVAP CANISTER FOR HEV'S
Vehicles sold in North America are required to adsorb diurnal, running loss and refueling vapors inside a carbon canister. Hydrocarbon (HC) vapors contribute to SMOG and it is undesirable to emit them into the atmosphere. Canister is typically cleaned or purged using engine vacuum during combustion. HEV and Start/Stop vehicles utilize a special Vapor Blocking Valve (VBV) to improve purge efficiency. This is due to limited engine run time in those vehicles. While purging, the VBV is commanded closed. This way, the canister is cleaned out without further loading with vapors from the fuel tank. At key off, VBV is typically open and the Evap system is vented to atmosphere. Cold Start Emissions is a major source of hydrocarbon emissions into the atmosphere. During cold starts, the catalyst is still not warm yet and hence hydrocarbons escape into the atmosphere. During cold starts, software controls typically retard the spark to generate heat and warm up the catalyst quickly. This warm-up takes 15-30 seconds. Up to 80% of HC tailpipe emissions during a drive cycle occurs during a cold start. Even if the engine is not cold, during the cranking event, residual HC in the cylinders or exhaust manifold from the prior key off event (from leaky injectors or intake manifold fuel puddling) can still exit to the atmosphere via the exhaust pipe.
The method reduces HC emissions during every crank event by re-routing...