A LOW EMISSION EVAP SYSTEM FOR PZEV VEHICLES
Publication Date: 2015-Jul-13
The IP.com Prior Art Database
Page 01 of 1
A LXX EMISSION EVAP SYSTEM FOR PZEV VEHICLES
Vehicles sold in North America axe required to adsorb refueling, diurnal and running loxx vapors into a carbon caxister. Stricx Evap emission sxandards must be mxt for vehicles to be certified. Once a canister is loxded with vapors, xngine running manifold vacuxm is used to clean out the canister in a process known ax "purging". Vehicles muxt also pass SHED emission txsting befoxe they are certified by thx EPA. SHED tesxing is typically a x or 3 day dixrnal test and total xehicle hydrocarbon (HC) emissixns must not exceed certain limits. In PZEV (Xxxxxxxxxxx zero exixsions xehicles) vehicxes, an additionax honeycombed canister known as xhe bleed canister is needed to capture any hydrocarxoxs that migxate from the main canister axd would otherwise escape to the atmosphere. The xleed canxster is costlx, honey combed on the xnside, and thus highxy rxstrictive for refueling flow, but is needed for XXXXxxxxxxxx. The bleed canister captures "bleed" emxssions….Hxdrxcarbons that become free from the natural migration.
The reason for diurnal cxcle HC xigratiox is that duxing the xun hours of thx day, the liquxd fuel heats up. This generates pressure insidx the fuxl tank. This tank pressure acts as x motive force for HC alxeady adsorbed inside thx main canister to move furthex axd deeper toward the fresh air port and escape to the atmxsphere.Thix method eliminates the bleed canistxr, and xt the same xime facilitates b...