Air-fuel ratio control apparatus of internal combustion engine

An air-fuel ratio control apparatus of an internal combustion engine for storing evaporated fuel generated in a fuel tank in a canister and purging off the evaporated fuel stored in the canister to an intake side of the internal combustion engine through a blow-off passage together with air, comprising:

• air-fuel ratio detecting means for detecting an air-fuel ratio of said internal combustion engine;
• air-fuel ratio feedback means for making feedback control of the air-fuel ratio of the air-fuel mixture supplied to the internal combustion engine in accordance with the air-fuel ratio detected by the air-fuel ratio detecting means;
• a flow rate control valve for changing a purge rate of air containing the evaporated fuel purged off to the intake side of said internal combustion engine from said canister through said blow-off passage;
• purge rate control means for controlling the purge rate by said flow rate control valve in accordance with the state of the engine;
• concentration detecting means for detecting the concentration of said evaporated fuel;
• purge reacting fuel quantity correcting means for correcting the fuel quantity so that the air-fuel ratio shows a predetermined value in accordance with the evaporated fuel concentration detected by said concentration detecting means and the purge rate by said purge rate control means;
• operating area detecting means for detecting a plurality of operating areas including idling and non-idling of the internal combustion engine;
• learning value storage means for storing air-fuel ratio learning values in accordance with a plurality of operating areas including idling and non-idling of the internal combustion engine;
• deviation detecting means for detecting the deviation by comparing an air-fuel ratio feedback value by said air-fuel ratio feedback means with a reference value;
• uniform learning control means for increasing or decreasing fuel quantity so that the deviation from the reference value detected by said deviation detecting means shows a predetermined value or below at both times when the operation state of an internal combustion engine is detected to be idling and when it is detected to be non-idling by said operating area detecting means before purge rate control is started by said purge rate control means;
• uniform learning value renewal means for renewing learning values of said learning value storage means based on increase and decrease quantity of fuel of said uniform learning control means when said deviation shows a predetermined value or below at both times when the operation state of an internal combustion engine is detected to be idling and when it is detected to be non-idling by said operating area detecting means by increase and decrease of fuel quantity by the uniform learning control means;
• purge start permit means for permitting the start of purge rate control by said purge rate control means after renewal of the learning value by the uniform learning value renewal means;
• and
• learning value renewal by area means for renewing learning values of said learning value storage means by area based on the air-fuel ratio feedback value by said air-fuel ratio feedback control means after renewal of the learning values by said uniform learning value renewal means.