Patent ID: 6513509
Filing Date: 2003-02-04
Classification: F02D

Abstract:
A device for controlling an air-fuel ratio of an internal combustion engine comprising:an injector for injecting an amount of fuel into an internal combustion engine; an air-fuel-ratio sensor installed in an exhaust pipe of said internal combustion engine for detecting a stoichiometric air-fuel ratio; and a control circuit for controlling said injector based upon operation conditions of said internal combustion engine and an air-fuel-ratio signal generated by said air-fuel-ratio sensor; wherein said control circuit includes: air-fuel-ratio correction means for correcting said amount of fuel depending upon a target air-fuel ratio that varies according to said operation conditions; feedback control condition-determining means for determining conditions for controlling the air-fuel ratio feedback of said internal combustion engine depending upon said operation conditions; feedback control means for controlling the air-fuel ratio of said internal combustion engine so as to come into agreement with said target air-fuel ratio in a feedback operation region where said control conditions are permitted; and air-fuel-ratio learning means for determining learning correction values for every operation region based on a control quantity of said feedback control means; wherein in an open-loop operation region where said control conditions are not permitted, said feedback control means temporarily executes a feedback control operation, and said air-fuel-ratio learning means determines said learning correction values in said open-loop operation region during said feedback control operation.