Patent ID: 6234156
Filing Date: 2001-05-22
Classification: F02D,F02M

Abstract:
An air-fuel ratio controller for an internal combustion engine, wherein the controller controls the air-fuel ratio of an air-fuel mixture to be burned according to the running state of the engine, wherein the engine includes an air intake passage connected to a combustion chamber, in which air flows to the combustion chamber, a fuel tank for storing liquid fuel, an injector for supplying the liquid fuel to the combustion chamber, and a fuel vapor supply means for supplying fuel vapor vaporized in the fuel tank to the combustion chamber, the controller comprising:an air-fuel sensor for detecting the actual air-fuel ratio of the air-fuel mixture;an air-fuel ratio control means for controlling at least one of the amount of fuel supplied from the injector and the amount of air flowing in the air intake passage;a primary correcting means for setting a feedback coefficient to correct the difference between the actual air-fuel ratio and a predetermined target air-fuel ratio, wherein the feedback coefficient is feedback controlled; anda secondary correcting means for employing a change of the air-fuel ratio, which is caused by operation of the fuel vapor supplying means in the operation of the air-fuel ratio control means, to correct the difference between the actual air-fuel ratio and the target air-fuel ratio by cooperating with the primary correcting means, wherein the secondary correcting means judges, by referring to the running state and an operating history of the engine, whether to calculate one of an air-fuel ratio correction coefficient related to the difference between the actual air-fuel ratio and the target air-fuel ratio, a concentration coefficient related to the fuel concentration of the fuel vapor and the air-fuel ratio correction coefficient and the concentration coefficient at the same time, and whether to register the actual air-fuel ratio correction coefficient as a temporary value.