Control device of internal combustion engine

摘要

A control device of an internal combustion engine which is provided with an exhaust purification catalyst is provided with a downstream side air-fuel ratio sensor, a feed control means for controlling the fuel feed amount so that the air-fuel ratio of the exhaust gas becomes a target air-fuel ratio, and an excess/deficiency estimating means which estimates an oxygen excess/deficiency in the exhaust gas. The target air-fuel ratio is switched to a lean air-fuel ratio when the output air-fuel ratio of the downstream side air-fuel ratio sensor becomes a rich air-fuel ratio and is switched to the rich air-fuel ratio when the stored amount of oxygen of the exhaust purification catalyst after this becomes a switching reference amount or more. An absolute value of cumulative oxygen excess/deficiency at a time period during which the target air-fuel ratio is made the lean air-fuel ratio and an absolute value of cumulative oxygen excess/deficiency at a time period during which the target air-fuel ratio is made the rich air-fuel ratio are used as the basis to correct the target air-fuel ratio etc. so that the difference of these absolute values becomes small.

主权项

1. A control device of an internal combustion engine comprising an exhaust purification catalyst which is arranged in an exhaust passage of an internal combustion engine and which can store oxygen, which control device of an internal combustion engine comprises a downstream side air-fuel ratio detection device which is arranged at a downstream side of said exhaust purification catalyst in the exhaust flow direction and which detects an air-fuel ratio of exhaust gas flowing out from said exhaust purification catalyst, feed control means for controlling the feed of fuel which is fed to a combustion chamber of the internal combustion engine, and an excess/deficiency estimating means for estimating an oxygen excess/deficiency in said exhaust gas flowing into exhaust purification catalyst,
wherein said feed control means performs feedback control on the feed of fuel fed to the combustion chamber of the internal combustion engine so that said air-fuel ratio of the exhaust gas which flows into exhaust purification catalyst becomes a target air-fuel ratio, and when an air-fuel ratio detected by said downstream side air-fuel ratio detection device reaches a judgment air-fuel ratio which is offset to one side of either a rich side or lean side from the stoichiometric air-fuel ratio, said target air-fuel ratio is switched to an air-fuel ratio which is offset to the other side at an opposite side to that one side from the stoichiometric air-fuel ratio and when an amount of change of said stored amount of oxygen of the exhaust purification catalyst after said target air-fuel ratio is switched becomes a predetermined switching reference amount or more, said target air-fuel ratio is switched to an air-fuel ratio which is offset to the one side from the stoichiometric air-fuel ratio, and wherein an absolute value of cumulative oxygen excess/deficiency at a first time period from which said target air-fuel ratio is switched to an air-fuel ratio which is offset to the other side from the stoichiometric air-fuel ratio to when the amount of change of said stored amount of oxygen becomes said switching reference amount or more, constituting a first cumulative value of amount of oxygen, and an absolute value of cumulative oxygen excess/deficiency at a second time period from which said target air-fuel ratio is switched to an air-fuel ratio which is offset to the one side from the stoichiometric air-fuel ratio to when the air-fuel ratio detected by said downstream side air-fuel ratio detection device becomes said judgment air-fuel ratio or less, constituting a second cumulative value of amount of oxygen, are used as the basis to correct a parameter relating to the air-fuel ratio so that a difference between these first cumulative value of amount of oxygen and second cumulative value of amount of oxygen becomes smaller.