Canister purge device

Abstract

Abstract PURPOSE:To prevent air fuel ratio from fluctuation due to evaporated fuel gas by detecting through an O2 sensor in an exhaust system whether mixture is lean or rich and purging the evaporated fuel gas of a canister only when the air-fuel ratio is lean. CONSTITUTION:Evaporated fuel gas produced in a fuel tank 4 and the like is introduced into a canister 6 while an engine is stopped at high temperature in the summer or the like, and adsorbed and stored in active carbon in the interior. Since an O2 sensor 11 is neither activated nor produces electromotive force at start under the cold condition, a solenoid valve 9 is closed so that the evaporated fuel gas is not purged. Next, after the activation of the sensor 11, air-fuel ratio of mixture is detected. When the air-fuel ratio is rich, the electromotive force of the sensor 11 becomes high and the valve 9 is rendered non-conductive by a control circuit 12 so that the purge is not carried out. On the other hand, when the air-fuel ratio becomes lean in the normal constant speed travelling, it is detected by the sensor 11 and the valve 9 becomes conductive and is opened so that negative pressure in an intake pipe acts on a canister 6. Then adsorbed evaporated fuel gas is sucked into the intake pipe 2 together with the atmosphere for combustion so that the fluctuation of the air-fuel ratio can be restrained.

Inventors

• 👤 Minoru Saeki
• 👤 稔 佐伯

Bibliographic Details