| 主权项 |
1. A control apparatus for an internal combustion engine, comprising:
a catalyst disposed in an exhaust passage of said engine; a downstream air-fuel ratio sensor which is an oxygen concentration sensor, disposed in said exhaust passage and at a position downstream of said catalyst; a target air-fuel ratio determining section configured to determine, based on an output value of said downstream air-fuel ratio sensor, which a target air-fuel ratio being a target value of an air-fuel ratio of a gas flowing into said catalyst should be set to a target rich air-fuel ratio smaller than a stoichiometric air-fuel ratio or a target lean air-fuel ratio larger than said stoichiometric air-fuel ratio, and sets said determined one of said target rich air-fuel ratio and said target lean air-fuel ratio as said target air-fuel ratio; a fuel injection valve configured to inject a fuel to said engine; a fuel injection control section configured to determine a fuel injection amount being an amount of said fuel to be injected from said fuel injection valve according to said target air-fuel ratio, and to have said fuel having said determined fuel injection amount be injected from said fuel injection valve; and an evaporated fuel purge section configured to perform an evaporated fuel purge when a predetermined purge execution request condition is satisfied, said evaporated fuel purge being for introducing an evaporated fuel generated in a fuel tank storing said fuel supplied to said fuel injection valve into an intake passage of said engine, wherein, said target air-fuel ratio determining section is configured:
so as to determine that said target air-fuel ratio should be set to said target lean air-fuel ratio, when a change amount ΔVoxs of said output value Voxs of said downstream air-fuel ratio sensor per unit time is a positive value, and a magnitude |ΔVoxs| of said output value becomes larger than a rich determining threshold value dRichth; andso as to determine that said target air-fuel ratio should be set to said target rich air-fuel ratio, when said change amount ΔVoxs of said output value Voxs of said downstream air-fuel ratio sensor per unit time is a negative value, and said magnitude |ΔVoxs| of said output value becomes larger than a lean determining threshold value dLeanth; and said evaporated fuel purge section is configured:
so as to start said evaporated fuel purge when said target air-fuel ratio is set at said target rich air-fuel ratio at a purge execution request condition satisfied time point at which a state changes from a state in which said purge execution request condition is unsatisfied to a state in which said purge execution request condition is satisfied; andso as not to start said evaporated fuel purge when said target air-fuel ratio is set at said target lean air-fuel ratio at said purge execution request condition satisfied time point, and so as to thereafter start said evaporated fuel purge when said target air-fuel ratio is set at said target rich air-fuel ratio after a point in time at which said target air-fuel ratio was changed to said target rich air-fuel ratio. |
