Patent ID: 9212583
Filing Date: 2015-12-15
Classification: F01N,F02D,Y02A,Y02T

Abstract:
1. An air-fuel ratio control apparatus for an internal combustion engine, comprising: a catalyst provided in an exhaust passage of the internal combustion engine: a downstream air-fuel ratio sensor provided downstream of the catalyst in the exhaust passage; and an electronic control unit configured to control an air-fuel ratio of the engine, which is an air-fuel ratio of a gas mixture supplied to the engine, on a basis of an output value of the downstream air-fuel ratio sensor, wherein the electronic control unit is further configured to: determine whether or not a predetermined condition for predicting that the air-fuel ratio of the engine at a point in time in which an acceleration is performed is leaner than a stoichiometric air-fuel ratio, is fulfilled; and increase a concentration of a reducing agent in the catalyst when the predetermined condition is fulfilled over that when the predetermined condition is not fulfilled, by controlling the air-fuel ratio of the engine so that an average value of the air-fuel ratio of the engine obtained when the predetermined condition is fulfilled, becomes less than the average value of the air-fuel ratio of the engine obtained when the predetermined condition is not fulfilled, wherein the predetermined condition is a condition fulfilled when at least one of the following conditions is fulfilled: an intake air amount correlation value that increases as an intake air amount of the engine increases is greater than a low-side air amount threshold and less than a high-side air amount threshold that is greater than the low-side air amount threshold, or a speed of a vehicle carrying the engine is greater than a low-side speed threshold and less than a high-side speed threshold that is greater than the low-side speed threshold.