Patent ID: 8266898

Claim:
A control apparatus for an internal combustion engine that is provided in an exhaust passage with a particulate filter for trapping particulate matter contained in exhaust gas, and that performs stoichiometric burn operation at a stoichiometric air-fuel ratio, the control apparatus comprising an electronic control unit (ECU) including control logic configured to perform the following logic steps during deceleration: (a) determine whether an amount of particulate matter (PM) on the PM filter is greater than a first predetermined PM amount, wherein if the amount of PM on the PM filter is greater than the first predetermined PM amount, the ECU performs step (b), else the ECU performs step (c); (b) determine whether a temperature of the PM filter is greater than a first predetermined temperature, wherein if the temperature of the PM filter is greater than the first predetermined temperature, the ECU performs fuel cut prohibition control during deceleration and returns to step (a), else the ECU performs step (c); (c) end fuel cut prohibition control and perform normal fuel cut control during deceleration, if the ECU was performing fuel cut prohibition control, or maintain slight-lean control, if the ECU was performing slight-lean control, or maintain normal fuel cut control, if the ECU was performing normal fuel cut control; and then (d) determine whether the amount of PM on the PM filter is greater than a second predetermined PM amount, the second predetermined PM amount being less than the first predetermined PM amount, wherein if the amount of PM on the PM filter is greater than the second predetermined PM amount, the ECU performs step (e), else the ECU performs step (f); (e) determine whether the temperature of the PM filter is greater than a second predetermined temperature, the second predetermined temperature being less than the first predetermined temperature, wherein if the temperature of the PM filter is greater than the second predetermined temperature, the ECU performs slight-lean control during deceleration and returns to step (a), else the ECU performs step (f); (f) end slight-lean control and perform normal fuel cut control during deceleration, if the ECU was performing slight-lean control, or maintain normal fuel cut control if the ECU was performing normal fuel cut control during deceleration; wherein slight-lean control is where the air-fuel ratio of the exhaust gas is controlled so that an atmosphere of the particulate filter is slightly leaner than the stoichiometric air-fuel ratio.