EXHAUST PURIFICATION SYSTEM FOR INTERNAL COMBUSTION ENGINE

摘要

The objective of the present invention is to provide an exhaust purification system that is capable of purifying exhaust gas during both lean and stoichiometric driving. The exhaust purification system is equipped with: a feedback-use identifier, which identifies parameter values such that the error between the output value from a LAF sensor and the estimated value for the LAF sensor output as obtained from a model equation is minimized; and a stoichiometric driving mode controller. The controller performs feedback control and thereby determines the fuel injection amount such that in the stoichiometric driving mode the equivalence ratio value as calculated from the parameters reaches a target value which is set such that a three-way purification reaction occurs in an under-engine catalyst. The identifier identifies the model parameters before feedback control is initiated by the controller.

主权项

1. An exhaust purification system of an internal combustion engine which switches between a lean operation mode to set an equivalence ratio of air-fuel mixture lean and a stoichiometric operation mode to set the equivalence ratio of air-fuel mixture stoichiometric under a predetermined condition, comprising:
a catalytic purification device which is arranged at an exhaust passage of the engine and which includes at least one catalyst at which a three-way purification reaction and a NOx purification reaction in the lean operation mode proceed; an exhaust gas sensor which detects an equivalence ratio of exhaust gas; a fuel injection amount determining unit which determines a fuel injection amount of the engine; and a parameter identifying unit which models a system from a parameter related to the fuel injection amount to a parameter related to an output of the exhaust gas sensor with a model formula including model parameters, and which identifies values of the model parameters to minimize an error between an estimated value of the parameter related to the output of the exhaust gas sensor obtained from the model formula and a value of the parameter related to the output of the exhaust gas sensor, wherein the fuel injection amount determining unit determines the fuel injection amount so that the equivalence ratio of air-fuel mixture becomes lean based on a required drive force of a driver in the lean operation mode and determines the fuel injection amount by performing feedback control so that a value of an equivalence ratio parameter calculated using the model parameters reaches a target value which is set so that the three-way purification reaction occurs at the catalyst in the stoichiometric operation mode; and the parameter identifying unit identifies the values of the model parameters to minimize the error before the feedback control is started.