Patent ID: 6032659
Filing Date: 2000-03-07
Classification: F02D,Y02T

Abstract:
An air/fuel ratio controller comprising:an air/fuel ratio sensor which can vary its output linearly when detecting an air/fuel ratio in an internal combustion engine;fuel supplying means for supplying fuel to the engine;basic fuel amount calculating means for calculating a basic fuel supply amount in accordance with engine speed and engine load of the engine;target air/fuel ratio generating means for generating a target air/fuel ratio in accordance with operating conditions of the engine;air/fuel ratio correction amount generating means for generating an air/fuel ratio correction amount in accordance with a difference between the air/fuel ratio detected by the air/fuel ratio sensor and the target air/fuel ratio set by the target air/fuel ratio generating means;air/fuel ratio control means for controlling a fuel supply amount to be supplied by the fuel supplying means, based on the basic fuel supply amount calculated by the basic fuel amount calculating means and the air/fuel ratio correction amount set by the air/fuel ratio correction amount generating means;fuel correction determining means for determining that an instruction to provide a correction amount that exceeds a predetermined amount in accordance with a change of the operating conditions of the engine has been outputted with respect to the basic fuel supply amount calculated by the basic fuel amount calculating means; andsensor diagnostic means for, if the fuel correction determining means determines that an instruction to provide a correction amount that exceeds a predetermined amount in accordance with a change of the operating conditions of the engine has been outputted with respect to the basic fuel supply amount calculated by the basic fuel amount calculating means, checking for an abnormality of the air/fuel ratio sensor by comparing a change of the target air/fuel ratio set by the target air/fuel ratio generating means and a change of the air/fuel ratio correction amount set by the air/fuel ratio correction amount generating means.