Patent ID: 6729319
Filing Date: 2004-05-04
Classification: F02D,F02M

Abstract:
An apparatus for controlling the air-fuel ratio of air-fuel mixture drawn into a combustion chamber of an engine, wherein an intake passage of the engine is connected to a canister by a purge line, wherein the canister adsorbs fuel vapor generated in the fuel tank and permits the adsorbed fuel vapor to be separated, wherein gas containing fuel vapor is purged as purge gas from the canister to the intake passage through the purge line, the apparatus comprising:a purge controlling device for adjusting purge flow rate, which is the flow rate of the purge gas flowing through the purge line; a sensor for detecting the air-fuel ratio of the air-fuel mixture; a computer for setting the amount of fuel supplied to the combustion chamber such that the detected air-fuel seeks a target air-fuel ratio; wherein the computer computes the purge flow rate based on the state of the purge controlling device, and computes vapor concentration, which is the concentration of the fuel vapor contained in the purge gas, based on the difference between the detected air-fuel ratio and the target air-fuel ratio; wherein, in accordance with changes of the computed purge flow rate, the computer obtains a concentration correction value for correcting the computed vapor concentration; wherein, by taking into consideration of the difference between the time at which the purge flow rate is computed and the time at which purge gas having the computed flow rate is drawn into the combustion chamber, the computer corrects the computed vapor concentration by using the concentration correction value; and wherein the computer sets the fuel supply amount in accordance with the computed purge flow rate and the corrected vapor concentration.