| 主权项 |
1. A fuel vapor recovery canister comprising
a filter bed housing formed to include an interior region, a canister inlet opening into an upstream portion of the interior region, and a canister outlet opening into a downstream portion of the interior region and communicating with the atmosphere, a hydrocarbon filter located in the interior region of the filter bed housing, the hydrocarbon filter including a first carbon bed positioned to lie in fluid communication with any pressurized fuel vapor and vacuum extant in the upstream portion of the interior region and a second carbon bed positioned to lie in fluid communication with any atmosphere extant in the downstream portion of the interior region and in spaced-apart relation to the first carbon bed to define a flow-controller compartment therebetween, and a two-stage vapor flow controller positioned to lie in the flow-controller compartment in fluid communication with each of the first and second carbon beds of the hydrocarbon filter and configured to provide means for allowing pressurized fuel vapor to flow from the first carbon bed to the second carbon bed to cause hydrocarbons entrained in the pressurized fuel vapor to be deposited on the first and second carbon beds during refueling of a vehicle fuel tank associated with the canister inlet of the filter bed housing and for allowing atmospheric air to be drawn, in sequence, through the canister outlet, second carbon bed, flow-controller compartment, first carbon bed, and canister inlet when a vacuum is applied to the first carbon bed via the canister inlet to cause hydrocarbon deposited on the first and second carbon beds to be entrained in the atmospheric air for delivery to a vehicle engine associated with the canister inlet during a hydrocarbon purge cycle to purge hydrocarbons that had been stored on the first and second carbon beds so that those hydrocarbons can exit the filter bed housing through the canister inlet to be burned in the vehicle engine, wherein the two-stage vapor flow controller includes a valve housing formed to include a valve chamber, a first-bed vent aperture opening into the chamber and lying in fluid communication with the first carbon bed, a second-bed vent aperture opening into the valve chamber and lying in fluid communication with the second carbon bed, and an annular valve seat positioned to lie in the chamber between the first-bed vent aperture and the second-bed vent aperture and arranged to face in a direction toward the second carbon bed to define a first-bed zone in the valve chamber between the first-bed vent aperture and the annular valve seat and a second-bed zone in the valve chamber between the annular valve seat and the second-bed vent aperture, the annular valve seat is formed to include a vapor discharge aperture opening into each of the first-bed zone and the second-bed zone, and the two-stage vapor flow controller includes a pressure-relief valve located in the first-bed zone and formed to include a vapor intake aperture, a pressure-relief control spring arranged to act against the valve housing normally to yieldably urge the pressure-relief valve to engage the annular valve seat, a vacuum-relief valve positioned to lie between the pressure-relief valve and the first-bed vent aperture, and a vacuum-relief control spring arranged to act against the valve housing normally to yieldably urge the vacuum-relief valve to engage the pressure-relief valve to close the vapor intake aperture formed in the pressure-relief valve. |
