Evaporative emission control device

Claim 1

In an engine having a fuel supply system including a fuel tank, a main canister containing a main body of fuel vapor storage material, a vent line means for delivering fuel vapor from the fuel supply system to the storage material, a throttle valve controlled induction passage means for delivering air to the engine, the induction passage means including a heat stove for heating air and having an air inlet located in heat exchange relationship to the exhaust manifold of the engine and an air outlet for supplying engine heated air, as controlled by a snorkel damper mechanism, into the induction passage means upstream of the throttle valve, a canister air vent line to the canister, and a purge means from the canister for delivering fuel vapor stored in the storage material therein to the induction passage downstream of the throttle valve, the improvement comprising: a fuel vapor secondary canister containing a secondary bed of fuel vapor storage material therein; said secondary canister defining an air flow path therethrough and being connected at one end to the air outlet of the air heat stove and having its other end connected in flow communication as controlled by the snorkel damper mechanism with the induction passage means upstream of the throttle valve; said secondary bed of vapor storage material being positioned in said flow path between opposite ends thereof; and a port means in said secondary canister opening at one end into said secondary bed on the downstream side thereof in terms of heated air flow through said air path and connected at its opposite end to the canister vent line, whereby any flow of fuel vapor from the main canister will be stored in said secondary bed of fuel vapor storage material in said secondary canister so that during engine operation heated air flowing through said secondary canister will rapidly purge all fuel vapor therefrom.