Double air-fuel ratio sensor system having improved response characteristics

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 the concentration of a specific component in the exhaust gas, comprising the steps of:

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 the concentration of a specific component in the exhaust gas, comprising the steps of:

Claim 7

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 the concentration of a specific component in the exhaust gas, comprising the steps of: comparing the output of said upstream-side air-fuel ratio sensor with a first fixed reference voltage; performing a delay operation upon the comparison result of the output of said upstream-side air-fuel ratio sensor with said first fixed reference; changing a first air-fuel ratio correction amunt in accordance with the delayed comparison result of the output of said upstream-side air-fuel ratio sensor with said first fixed reference voltage; comparing the output of said downstream-side air-fuel ratio sensor with a second fixed reference voltage; performing a delay operation upon the comparison result of the output of said downstream-side air-fuel ratio sensor with said fixed second reference voltage; changing a second air-fuel ratio correction amount in accordance with the delayed comparison result of the output of said downstream side air-fuel ratio sensor with said second reference voltage; and adjusting an actual air-fuel ratio in accordance with said first and second air-fuel ratio correction amounts.

Claim 8

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 the concentration of a specific component in the exhaust gas, comprising the steps of: comparing the output of said upstream-side air-fuel ratio sensor with a first fixed reference voltage; performing a delay operation upon the comparison result of the output of said upstream-side air-fuel ratio sensor with said first fixed reference; changing a first air-fuel ratio correction amunt in accordance with the delayed comparison result of the output of said upstream-side air-fuel ratio sensor with said first fixed reference voltage; comparing the output of said downstream-side air-fuel ratio sensor with a second fixed reference voltage; performing a delay operation upon the comparison result of the output of said downstream-side air-fuel ratio sensor with said fixed second reference voltage; changing a second air-fuel ratio correction amount in accordance with the delayed comparison result of the output of said downstream side air-fuel ratio sensor with said second reference voltage; and adjusting an actual air-fuel ratio in accordance with said first and second air-fuel ratio correction amounts.

Claim 12

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 the concentration of a specific component in the exhaust gas, comprising the steps of: comparing the output of said upstream-side air-fuel ratio sensor with a first fixed reference voltage; generating a first delay signal by performing a delay operation upon the comparison result of the output of said upstream-side air-fuel ratio sensor with said first fixed reference voltage; changing an air-fuel ratio correction amount in accordance with said first delay signal; comparing the output of said downstream-side air-fuel ratio sensor with a second fixed reference voltage; generating a second delay signal by performing a delay operation upon the comparison result of the output of said downstream-side air-fuel ratio sensor with said second fixed reference voltage; changing a rich skip amount and/or a lean skip amount in accordance with said second delay signal, said air-fuel ratio correcting amount being remarkably increased by said rich skip amount at a switching of the comparison result of said upstream-side air-fuel ratio sensor from the rich side to the lean side, said air-fuel ratio correction amount being remarkably decreased by said lean skip amount at a switching of the comparison result of said upstream-side air-fuel ratio sensor from the lean side to the rich side; and adjusting an actual air-fuel ratio in accordance with said air-fuel ratio correction amount.

Claim 13

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 the concentration of a specific component in the exhaust gas, comprising the steps of: comparing the output of said upstream-side air-fuel ratio sensor with a first fixed reference voltage; generating a first delay signal by performing a delay operation upon the comparison result of the output of said upstream-side air-fuel ratio sensor with said first fixed reference voltage; changing an air-fuel ratio correction amount in accordance with said first delay signal; comparing the output of said downstream-side air-fuel ratio sensor with a second fixed reference voltage; generating a second delay signal by performing a delay operation upon the comparison result of the output of said downstream-side air-fuel ratio sensor with said second fixed reference voltage; changing a rich skip amount and/or a lean skip amount in accordance with said second delay signal, said air-fuel ratio correcting amount being remarkably increased by said rich skip amount at a switching of the comparison result of said upstream-side air-fuel ratio sensor from the rich side to the lean side, said air-fuel ratio correction amount being remarkably decreased by said lean skip amount at a switching of the comparison result of said upstream-side air-fuel ratio sensor from the lean side to the rich side; and adjusting an actual air-fuel ratio in accordance with said air-fuel ratio correction amount.

Claim 17

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 the concentration of a specific component in the exhaust gas, comprising the steps of: comparing the output of said upstream-side air-fuel ratio sensor with a first fixed reference voltage; generating a first delay signal by performing a delay operation upon the comparison result of the output of said upstream-side air-fuel ratio sensor with said first fixed reference voltage; changing an airfuel ratio correction amount in accordance with said first delay signal; comparing the output of said downstream-side air-fuel ratio sensor with a second fixed reference voltage; generating a second delay signal by performing a delay operation upon the comparison result of the output of said downstream-side air-fuel ratio sensor with said second fixed reference voltage; changing a rich integration amount and/or a lean integration amount in accordance with said second delay signal, said air-fuel ratio correction amount being gradually increased by said rich integration amount at a switching of the comparison result of said upstream-side air-fuel ratio sensor from the rich side to the lean side, said air-fuel ratio correction amount being gradually decreased by said lean integration amount at a switching of the comparison result of said upstream-side air-fuel ratio sensor from the lean side to the rich side; and adjusting an actual air-fuel ratio in accordance with said air-fuel ratio correction amount.

Claim 18

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 the concentration of a specific component in the exhaust gas, comprising the steps of: comparing the output of said upstream-side air-fuel ratio sensor with a first fixed reference voltage; generating a first delay signal by performing a delay operation upon the comparison result of the output of said upstream-side air-fuel ratio sensor with said first fixed reference voltage; changing an airfuel ratio correction amount in accordance with said first delay signal; comparing the output of said downstream-side air-fuel ratio sensor with a second fixed reference voltage; generating a second delay signal by performing a delay operation upon the comparison result of the output of said downstream-side air-fuel ratio sensor with said second fixed reference voltage; changing a rich integration amount and/or a lean integration amount in accordance with said second delay signal, said air-fuel ratio correction amount being gradually increased by said rich integration amount at a switching of the comparison result of said upstream-side air-fuel ratio sensor from the rich side to the lean side, said air-fuel ratio correction amount being gradually decreased by said lean integration amount at a switching of the comparison result of said upstream-side air-fuel ratio sensor from the lean side to the rich side; and adjusting an actual air-fuel ratio in accordance with said air-fuel ratio correction amount.

Claim 22

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 the concentration of a specific component in the exhaust gas, comprising the steps of: comparing the output of said upstream-side air-fuel sensor with a first fixed reference voltage; generating a first delay signal by performing a delay operation upon the comparison result of the output of said upstream-side air-fuel ratio sensor with said first fixed reference voltage; changing an air-fuel ratio correction amount in accordance with said first delay signal; comparing the output of said downstream-side air-fuel ratio sensor with a second fixed reference voltage; generating a second delay signal by performing a delay operation upon the comparison result of the output of said downstream-side air-fuel ratio sensor with said second fixed reference voltage; changing a rich delay time period and/or a lean delay time period for said first delay signal in accordance with said second delay signal, the comparison result of said upstream-side air-fuel ratio sensor switched from the lean side to the rich side being delayed by said rich delay time period, the comparison result of said upstream-side air-fuel ratio sensor switched from the rich side to the lean side being delayed by said lean delay time period; and adjusting an actual air-fuel ratio in accordance with said air-fuel ratio correction amount.

Claim 23

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 the concentration of a specific component in the exhaust gas, comprising the steps of: comparing the output of said upstream-side air-fuel sensor with a first fixed reference voltage; generating a first delay signal by performing a delay operation upon the comparison result of the output of said upstream-side air-fuel ratio sensor with said first fixed reference voltage; changing an air-fuel ratio correction amount in accordance with said first delay signal; comparing the output of said downstream-side air-fuel ratio sensor with a second fixed reference voltage; generating a second delay signal by performing a delay operation upon the comparison result of the output of said downstream-side air-fuel ratio sensor with said second fixed reference voltage; changing a rich delay time period and/or a lean delay time period for said first delay signal in accordance with said second delay signal, the comparison result of said upstream-side air-fuel ratio sensor switched from the lean side to the rich side being delayed by said rich delay time period, the comparison result of said upstream-side air-fuel ratio sensor switched from the rich side to the lean side being delayed by said lean delay time period; and adjusting an actual air-fuel ratio in accordance with said air-fuel ratio correction amount.

Claim 27

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 aair-fuel ratio sensors disposed upstream and downstream, respectively, of said catalyst converter for detecting the concentration of a specific component in the exhaust gas, said apparatus comprising: means for comparing the output of said upstream side air-fuel ratio sensor with a first fixed reference voltage; means for a performing a delay operation upon the comparison result of the output of said upstream-side air-fuel ratio sensor with said first fixed reference voltage; means for comparing the output of said downstream-side air-fuel ratio sensor with a second fixed reference voltage; means for performing a delay operation upon the comparison result of the output of said downstream-side air-fuel ratio sensor with said second fixed reference voltage; and means for adjusting an actual air-fuel ratio in accordance with the delayed comparison resuIts of the outputs of said upstream-side and downstream-side air-fuel ratio sensors with said first and second fixed reference voltages, respectively.

Claim 28

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 aair-fuel ratio sensors disposed upstream and downstream, respectively, of said catalyst converter for detecting the concentration of a specific component in the exhaust gas, said apparatus comprising: means for comparing the output of said upstream side air-fuel ratio sensor with a first fixed reference voltage; means for a performing a delay operation upon the comparison result of the output of said upstream-side air-fuel ratio sensor with said first fixed reference voltage; means for comparing the output of said downstream-side air-fuel ratio sensor with a second fixed reference voltage; means for performing a delay operation upon the comparison result of the output of said downstream-side air-fuel ratio sensor with said second fixed reference voltage; and means for adjusting an actual air-fuel ratio in accordance with the delayed comparison resuIts of the outputs of said upstream-side and downstream-side air-fuel ratio sensors with said first and second fixed reference voltages, respectively.

Claim 31

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 the concentration of a specific component in the exhaust gas, said apparatus comprising: means for comparing the output of said upstream-side air-fuel ratio sensor with a first fixed reference voltage; means for performing a delay operation upon the comparison result of the output of said upstream-side air-fuel ratio sensor with said first fixed reference; means for changing a first air-fuel rato correction amount in accordance wiht the delayed comparison result of the output of said upstream-side air-fuel ratio sensor with said first fixed reference voltage; means for comparing the output of said downstream-side air-fuel ratio sensor with a second fixed reference voltage; means for performing a delay operation upon the comparison result of the output of said downstream-side air-fuel ratio sensor with sid fixed second reference voltage; means for changing a second air-fuel ratio correction amount in accordance ith the delayed comparison result of the output of said downstream side air-fuel ratio sensor with said second reference voltage; and means for adjusting an actual air-fuel ratio in accordance with said first and second and second air-fuel ratio correction amounts.

Claim 32

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 the concentration of a specific component in the exhaust gas, said apparatus comprising: means for comparing the output of said upstream-side air-fuel ratio sensor with a first fixed reference voltage; means for performing a delay operation upon the comparison result of the output of said upstream-side air-fuel ratio sensor with said first fixed reference; means for changing a first air-fuel rato correction amount in accordance wiht the delayed comparison result of the output of said upstream-side air-fuel ratio sensor with said first fixed reference voltage; means for comparing the output of said downstream-side air-fuel ratio sensor with a second fixed reference voltage; means for performing a delay operation upon the comparison result of the output of said downstream-side air-fuel ratio sensor with sid fixed second reference voltage; means for changing a second air-fuel ratio correction amount in accordance ith the delayed comparison result of the output of said downstream side air-fuel ratio sensor with said second reference voltage; and means for adjusting an actual air-fuel ratio in accordance with said first and second and second air-fuel ratio correction amounts.

Claim 36

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 the concentration of a specific component in the exhaust gas, said apparatus comprising: means for comparing the output of said upstream-side air-fuel ratio sensor with a first fixed reference voltage; means for generating a first delay signal by performing a delay operation upon the comparison result of the output of said upstream-side air-fuel ratio sensor with said first fixed reference voltage; means for changing an air-fuel ratio correction amount in accordance with said first delay signal; means for comparing the output of said downstream-side air-fuel ratio sensor with a second fixed reference voltage; means for generating a second delay signal by performing a delay operation upon the comparison result of the output of said downstream-side air-fuel ratio sensor with said second fixed reference voltage; means for changing a rich skip amount and/or a lean skip amount in accordance with said second delay signal, said air-fuel ratio correcting amount being remarkably increased by said rich skip amount at a switching of the comparison result of said upsteam-side air-fuel ratio sensor from the rich side to the lean side, said air-fuel ratio correction amount being remarkably decreased by said lean skip amount at a switching of the comparison result of said upstream-side air-fuel ratio sensor from the lean side to the rich side; and means for adjusting an actual air-fuel ratio in accordance with said air-fuel ratio correction amount.

Claim 37

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 the concentration of a specific component in the exhaust gas, said apparatus comprising: means for comparing the output of said upstream-side air-fuel ratio sensor with a first fixed reference voltage; means for generating a first delay signal by performing a delay operation upon the comparison result of the output of said upstream-side air-fuel ratio sensor with said first fixed reference voltage; means for changing an air-fuel ratio correction amount in accordance with said first delay signal; means for comparing the output of said downstream-side air-fuel ratio sensor with a second fixed reference voltage; means for generating a second delay signal by performing a delay operation upon the comparison result of the output of said downstream-side air-fuel ratio sensor with said second fixed reference voltage; means for changing a rich skip amount and/or a lean skip amount in accordance with said second delay signal, said air-fuel ratio correcting amount being remarkably increased by said rich skip amount at a switching of the comparison result of said upsteam-side air-fuel ratio sensor from the rich side to the lean side, said air-fuel ratio correction amount being remarkably decreased by said lean skip amount at a switching of the comparison result of said upstream-side air-fuel ratio sensor from the lean side to the rich side; and means for adjusting an actual air-fuel ratio in accordance with said air-fuel ratio correction amount.

Claim 41

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 an downstream side air-fuel ratio sensors disposed upstream and downstream, respectively, of said catalyst converter for detecting the concentration of a specific comonent in the exhaust gas, comprising: means for comparing the output of said upstream-side air-fuel ratio sensor with a first fixed reference voltage; means for generating a first delay signal by performing a delay operation upon the comparison result of the output of said upstream-side air-fuel ratio sensor with said first fixed reference voltage; means for changing an air-fuel ratio correction amount in accordance with said delay signal; means for comparing the output of said downstream-side air-fuel ratio sensor with a second fixed reference voltage; means for generating a second delay signal by performing a delay operation upon the comparison result of the output of said downstream-side air-fuel ratio sensor with said second fixed reference voltage; means for changing a rich integration amount and/or a lean integration amount in accordance with said second delay signal, said air-fuel ratio correction amount being gradually increased by said rich integration amount at a switching of the comparison result of said upstream-side air-fuel ratio sensor from the rich side to the lean side, said air-fuel ration correction amount being gradually decreased by said lean integration amount at a switching of the comparison result of said upstream-sie air-fuel ratio sensor from the lean side to the rich side; and means for adjusting an actual air-fuel ratio in accordance with said air-fuel ratio correction amount.

Claim 42

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 an downstream side air-fuel ratio sensors disposed upstream and downstream, respectively, of said catalyst converter for detecting the concentration of a specific comonent in the exhaust gas, comprising: means for comparing the output of said upstream-side air-fuel ratio sensor with a first fixed reference voltage; means for generating a first delay signal by performing a delay operation upon the comparison result of the output of said upstream-side air-fuel ratio sensor with said first fixed reference voltage; means for changing an air-fuel ratio correction amount in accordance with said delay signal; means for comparing the output of said downstream-side air-fuel ratio sensor with a second fixed reference voltage; means for generating a second delay signal by performing a delay operation upon the comparison result of the output of said downstream-side air-fuel ratio sensor with said second fixed reference voltage; means for changing a rich integration amount and/or a lean integration amount in accordance with said second delay signal, said air-fuel ratio correction amount being gradually increased by said rich integration amount at a switching of the comparison result of said upstream-side air-fuel ratio sensor from the rich side to the lean side, said air-fuel ration correction amount being gradually decreased by said lean integration amount at a switching of the comparison result of said upstream-sie air-fuel ratio sensor from the lean side to the rich side; and means for adjusting an actual air-fuel ratio in accordance with said air-fuel ratio correction amount.

Claim 46

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 the concentration of a specific component in the exhaust gas, said apparatus comprising: means for comparing the output of said upstream-side air-fuel sensor with a first fixed reference voltage; means for generating a first delay signal by performing a delay operation upon the comparison result of the output of said upstream-side air-fuel ratio sensor with said first fixed reference voltage; means for changing an air-fuel ratio correction amount in accordance with said first delay signal; means for comparing the output of said downstream-side air-fuel ratio sensor with a second fixed reference voltage; means for generating a second delay signal by performing a delay operation upon the comparison result of the output of said downstream-side air-fuel ratio sensor with said second fixed reference voltage; means for changing a rich delay time period and/or a lean delay time period for said first delay signal in accordance with said second delay signal, the comparison result of said upstream-side air-fuel ratio sensor switched from the lean side to the rich side being delayed by said rich delay time period, the comparison result of said upstream-side air-fuel ratio sensor switched from the rich side to the lean side being delayed by said lean delay time period; and means for adjusting an actual air-fuel ratio in accordance with said air-fuel ratio correction amount.

Claim 47

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 the concentration of a specific component in the exhaust gas, said apparatus comprising: means for comparing the output of said upstream-side air-fuel sensor with a first fixed reference voltage; means for generating a first delay signal by performing a delay operation upon the comparison result of the output of said upstream-side air-fuel ratio sensor with said first fixed reference voltage; means for changing an air-fuel ratio correction amount in accordance with said first delay signal; means for comparing the output of said downstream-side air-fuel ratio sensor with a second fixed reference voltage; means for generating a second delay signal by performing a delay operation upon the comparison result of the output of said downstream-side air-fuel ratio sensor with said second fixed reference voltage; means for changing a rich delay time period and/or a lean delay time period for said first delay signal in accordance with said second delay signal, the comparison result of said upstream-side air-fuel ratio sensor switched from the lean side to the rich side being delayed by said rich delay time period, the comparison result of said upstream-side air-fuel ratio sensor switched from the rich side to the lean side being delayed by said lean delay time period; and means for adjusting an actual air-fuel ratio in accordance with said air-fuel ratio correction amount.