Eaton Corp. has developed a new fuel-tank isolation valve aimed at solving the unique evaporative-emissions challenges of hybrid-electric vehicles (HEV). Its first production application is expected on MY2013 vehicles.
Eaton's valve is not a replacement for the traditional fuel-vapor management valve that is employed during purging of the evaporative-emissions canister. Rather, its primary purpose is to contain evaporative emissions within the fuel tank by isolating the tank from the canister under most conditions.
"This is necessary with pressurized hybrid fuel systems," explained Vaughn Mills, Eaton's Engineering Manager for Fuel Vapor Products.
He noted two key factors that limit an HEV's ability to purge its carbon canister of evap and refueling emissions—its typically small-displacement gasoline engine and the inconsistent "engine on" time related to HEV operating cycles.
"The fuel tank isolation valve prevents the evaporative emissions from loading into the carbon canister, so only the hydrocarbons from refueling are stored in the canister," Mills noted. "As a result, the engine's limited purge capacity can fully clean the canister."
Since a pressure buildup occurs when evaporative emissions are confined in the fuel tank, fuel vapor gets released if that pressure is not released prior to refueling.
"One of the functions of the fuel tank isolation valve is to depressurize the tank prior to opening the fuel cap door," Mills said. "The fuel vapor flow through the valve allows the pressure to drop to a point where it is safe to allow removal of the fuel cap for refueling the tank."
Eaton's new valve opens before refueling begins for vapor flow. Its development included 18 months of R&D.
"We are working with several OEMs on applications, but we cannot discuss the specific OEMs or programs at this time," said Matt Memmer, Sales Manager for Fuel and Powertrain Controls. He said Eaton officials also are seeking various patents for the product.