Evaporative emission control system for automotive vehicle

摘要

An evaporative emission control system which may be used in automotive vehicles is disclosed. The evaporative emission control system includes a canister, an inlet passage, a fuel vapor passage, an outlet valve, and an inlet valve. The air inlet passage is exposed at an end to the atmosphere and connected at the other end to the canister for drawing fresh air into the canister. The fuel vapor passage communicates between the canister and a fuel tank. When a pressure in the fuel tank is increased above a given level so that a difference in internal pressure between the fuel tank and the canister reaches a first value, the outlet valve establishes communication between the fuel tank and the canister to allow fuel vapor evaporated within the fuel tank to be drawn into the canister through the fuel vapor passage. Alternatively, when the pressure in the fuel tank is decreased below a given level so that a difference in internal pressure between the fuel tank and the canister reaches a second value, the inlet valve establishes communication between the fuel tank and the canister to allow the air to be drawn into the canister through the air inlet passage. The second value is so determined as to prevent the amount of fuel vapor generated within the fuel tank from being increased above a given value.