Patent Document ID: 20130166174
Application ID: 13687062
Patent Flag: 0

Claim One:
1. An air-fuel ratio control device which controls an air-fuel ratio of an internal combustion engine for an outboard motor provided with an O 2 sensor, which is disposed in an exhaust system of the internal combustion engine and varies in output characteristics in a vicinity of a logical air-fuel ratio, the air-fuel ratio control device comprising: an open loop controller that controls the air-fuel ratio to be a target air-fuel ratio based on an operating state of the internal combustion engine and a learned value; a feedback controller that shifts the target air-fuel ratio to a logical air-fuel ratio from a state that the target air-fuel ratio is controlled to be a predetermined air-fuel ratio on a lean side by the open loop controller, and feedback controls the air-fuel ratio to be the logical air-fuel ratio by using a feedback correction coefficient determined based on an output of the O 2 sensor; an average value calculator that calculates the average value of the feedback correction coefficient when the output of the O 2 sensor reverses from a lean side to a rich side and from the rich side to the lean side in the feedback control by the feedback controller; and a learned value calculator that calculates the learned value based on an average value at a time when the average value calculated by the average value calculator becomes substantially constant.