Fuel injection amount control system and fuel injection amount control device for multi-cylinder internal combustion engine

摘要

A fuel injection amount control system acquires a pre-correction air-fuel ratio imbalance index value that increases as the degree of ununiformity in the air-fuel ratio among cylinders increases, based on an output value of an upstream air-fuel ratio sensor, and obtains a value (intake air amount correlation value) corresponding to the intake air amount and a value (engine speed correlation value) corresponding to the engine speed over a period in which the pre-correction air-fuel ratio imbalance index value is acquired. Also, a post-correction air-fuel ratio imbalance index value is acquired by correcting the pre-correction air-fuel ratio imbalance index value based on the intake air amount correlation value and the engine speed correlation value, and the air-fuel ratio of the engine is controlled based on the post-correction air-fuel ratio imbalance index value.

主权项

1. A fuel injection amount control system of a multi-cylinder internal combustion engine, comprising:
a three-way catalyst mounted at a position downstream of an exhaust gathering portion of an exhaust passage of the engine into which exhaust gases emitted from a plurality of cylinders of the multi-cylinder internal combustion engine are collected; an upstream air-fuel ratio sensor located between the exhaust gathering portion of the exhaust passage and the three-way catalyst; a plurality of fuel injection valves each of which is arranged to inject fuel contained in an air-fuel mixture supplied to a combustion chamber of each of said plurality of cylinders; a designated fuel injection amount determining section that determines a designated fuel injection amount as a command value indicative of an amount of fuel injected from each of said plurality of fuel injection valves, by feedback-correcting the amount of fuel injected from said each fuel injection valve based on at least an output value of the upstream air-fuel ratio sensor, so that an air-fuel ratio of exhaust gas flowing into the three-way catalyst coincides with a target air-fuel ratio; an injection command signal sending section that sends an injection command signal to said plurality of fuel injection valves so that the fuel is injected from said each fuel injection valve in an amount corresponding to the designated fuel injection amount; a pre-correction index value acquiring section that acquires a pre-correction air-fuel ratio imbalance index value that increases as a degree of ununiformity in the air-fuel ratio of the air-fuel mixture supplied to the combustion chamber of each of said plurality of cylinders, among said plurality of cylinders, is larger, based on at least a value correlated with the output value of the upstream air-fuel ratio sensor; and a post-correction index value acquiring section that acquires an intake air amount correlation value that increases with increase of an intake air amount of the engine over an index value acquisition period as a period in which the pre-correction air-fuel ratio imbalance index value is acquired, and acquiring a post-correction air-fuel ratio imbalance index value by correcting the acquired pre-correction air-fuel ratio imbalance index value based on the acquired intake air amount correlation value.