Double air-fuel ratio sensor system having divided-skip function

Claim 1

A method for controlling the air-fuel ratio in an internal combustion engine having a catalyst converter for removing pollutants in the exhaust gas thereof, and upstream-side and downstream-side air-fuel ratio sensors disposed upstream and downstream, respectively, of said catalyst converter for detecting a concentration of a specific component in an exhaust gas, comprising the steps of: gradually changing an air-fuel ratio correction amount in accordance with the output of said upstream-side air-fuel ratio sensor; calculating a skip amount in accordance with the output of said downstream-side air-fuel ratio sensor; shifting said air-fuel ratio correction amount by said skip amount when the output of said upstream-side air-fuel ratio sensor is switched from the rich side to the lean side or vice versa; and adjusting an actual air-fuel ratio of said engine in accordance with said air-fuel ratio correction amount, said shifting step comprising the steps of: determining whether or not said skip amount is larger than a predetermined value; performing one skip operation upon said air-fuel ratio correction amount by said skip amount when said skip amount is not larger than said predetermined value; and performing a plurality of skip operations upon said air-fuel ratio correction amount by dividing said skip amount into a plurality of amounts when said skip amount is larger than said predetermined value.

Claim 2

A method for controlling the air-fuel ratio in an internal combustion engine having a catalyst converter for removing pollutants in the exhaust gas thereof, and upstream-side and downstream-side air-fuel ratio sensors disposed upstream and downstream, respectively, of said catalyst converter for detecting a concentration of a specific component in an exhaust gas, comprising the steps of: gradually changing an air-fuel ratio correction amount in accordance with the output of said upstream-side air-fuel ratio sensor; calculating a skip amount in accordance with the output of said downstream-side air-fuel ratio sensor; shifting said air-fuel ratio correction amount by said skip amount when the output of said upstream-side air-fuel ratio sensor is switched from the rich side to the lean side or vice versa; and adjusting an actual air-fuel ratio of said engine in accordance with said air-fuel ratio correction amount, said shifting step comprising the steps of: determining whether or not said skip amount is larger than a predetermined value; performing one skip operation upon said air-fuel ratio correction amount by said skip amount when said skip amount is not larger than said predetermined value; and performing a plurality of skip operations upon said air-fuel ratio correction amount by dividing said skip amount into a plurality of amounts when said skip amount is larger than said predetermined value.

Claim 6

An apparatus for controlling the air-fuel ratio in an internal combustion engine having a catalyst converter for removing pollutants in the exhaust gas thereof, and upstream-side and downstream-side air-fuel ratio sensors disposed upstream and downstream, respectively, of said catalyst converter for detecting a concentration of a specific component in an exhaust gas, comprising: means for gradually changing an air-fuel ratio correction amount in accordance with the output of said upstream-side air-fuel ratio sensor; means for calculating a skip amount in accordance with the output of said downstream-side air-fuel ratio sensor; means for shifting said air fuel ratio correction amount by said skip amount when the output of said upstream-side air-fuel ratio sensor is switched from the rich side to the lean side or vice versa; and means for adjusting an actual air-fuel ratio of said engine in accordance with said air-fuel ratio correction amount, said shifting means comprising: means for determining whether or not said skip amount is larger than a predetermined value; means for performing one skip operation upon said air-fuel ratio correction amount by said skip amount when said skip amount is not larger than said predetermined value; and means for performing a plurality of skip operations upon said air-fuel ratio correction amount by dividing said skip amount into a plurality of amounts when said skip amount is larger than said predetermined value.

Claim 7

An apparatus for controlling the air-fuel ratio in an internal combustion engine having a catalyst converter for removing pollutants in the exhaust gas thereof, and upstream-side and downstream-side air-fuel ratio sensors disposed upstream and downstream, respectively, of said catalyst converter for detecting a concentration of a specific component in an exhaust gas, comprising: means for gradually changing an air-fuel ratio correction amount in accordance with the output of said upstream-side air-fuel ratio sensor; means for calculating a skip amount in accordance with the output of said downstream-side air-fuel ratio sensor; means for shifting said air fuel ratio correction amount by said skip amount when the output of said upstream-side air-fuel ratio sensor is switched from the rich side to the lean side or vice versa; and means for adjusting an actual air-fuel ratio of said engine in accordance with said air-fuel ratio correction amount, said shifting means comprising: means for determining whether or not said skip amount is larger than a predetermined value; means for performing one skip operation upon said air-fuel ratio correction amount by said skip amount when said skip amount is not larger than said predetermined value; and means for performing a plurality of skip operations upon said air-fuel ratio correction amount by dividing said skip amount into a plurality of amounts when said skip amount is larger than said predetermined value.