Air-fuel ratio feedback system having improved activation determination for air-fuel ratio sensor
AssigneeToyota Jidosha Kabushiki Kaisha
InventorHiroki Matsuoka
Life of this patent
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Abstract
In an air-fuel ratio feedback control system including at least one air-fuel ratio sensor downstream of or within a catalyst converter provided in an exhaust gas passage, an actual air-fuel ratio is controlled in accordance with the output of the air-fuel ratio sensor, which is supplied to a pull-up type input circuit. The determination of whether or not the air-fuel ratio sensor is activated is carried out by comparing the output of the pull-up type input circuit with two distinct levels, thus obtaining a hysteretic determination.
Claims22
A method for controlling an air-fuel ratio in an internal combustion engine having a catalyst converter for removing pollutants in the exhaust gas thereof, 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 the exhaust gas, and a pull-up type input circuit for supplying a differential current to said downstream-side air-fuel ratio sensor and receiving an output of said downstream-side air-fuel ratio sensor, comprising the steps of:
- comparing an output of said pull-up type input circuit with a first level which is slightly higher than a rich state level of said pull-up type input circuit after said engine is warmed-up;
- comparing the output of said pull-up type input circuit with a second level higher than said first level;
- determining that said downstream-side air-fuel ratio sensor is in an activation state when the output of said pull-up type input circuit is lower than said first level;
- determining that said downstream-side air-fuel ratio sensor is in a non-activation state when the output of said pull-up type input circuit is higher than said second level;
- determining that said downstream-side air-fuel ratio sensor is in a previous state when the output of said pull-up type input circuit is between said first and second levels;
- and
- adjusting an actual air-fuel ratio in accordance with the outputs of said upstream-side and downstream-side air-fuel ratio sensors when said downstream-side air-fuel ratio sensor is in an activation state.
A method for controlling an air-fuel ratio in an internal combustion engine having a catalyst converter for removing pollutants in the exhaust gas thereof, an air-fuel ratio sensor disposed downstream of or within said catalyst converter, for detecting a concentration of a specific component in the exhaust gas, and a pull-up type input circuit for supplying a differential current to said air-fuel ratio sensor and receiving an output of said air-fuel ratio sensor, comprising the steps of:
- comparing the output of said pull-up type input circuit with a first level which is slightly higher than a rich state level of said pull-up input circuit after said engine is warmed-up;
- comparing the output of said pull-up type input circuit with a second level higher than said first level;
- determining that said downstream-side air-fuel ratio sensor is in an activation state when the output of said pull-up type input circuit is lower than said first level;
- determining that said downstream-side air-fuel ratio sensor is in a non-activation state when the output of said pull-up type input circuit is higher than said second level;
- determining that said downstream-side air-fuel ratio sensor is in a previous state when the output of said pull-up type input circuit is between said first and second levels;
- and
- adjusting an actual air-fuel ratio in accordance with the output of said downstream-side air-fuel ratio sensor when said air-fuel ratio sensor is in an activation state.
An apparatus for controlling an air-fuel ratio in an internal combustion engine having a catalyst converter for removing pollutants in the exhaust gas thereof, 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 the exhaust gas, and a pull-up type input circuit for supplying a differential current to said downstream-side air-fuel ratio sensor and receiving an output of said downstream-side air-fuel ratio sensor, comprising:
- means for comprising the output of said pull-up type input circuit with a first value which is slightly higher than a rich state level of said pull-up type input circuit after said engine is warmed-up;
- means for comprising the output of said pull-up type input circuit with a second value higher than said first value;
- means for determining that said downstream-side stream-side air-fuel ratio sensor is in an activation state when the output of said pull-up type input circuit is lower than said first value;
- determining that said downstream-side air-fuel ratio sensor is in a non-activation state when the output of said pull-up type input circuit is higher than said second value;
- means for determining that said downstream-side stream-side air-fuel ratio sensor is in a previous state when the output of said pull-up type input circuit is between said first and second values;
- and
- means for adjusting an actual air-fuel ratio in accordance with the outputs of said upstream-side and downstream-side air-fuel ratio sensors when said downstream-side air-fuel ratio sensor is in an activation state.
A method for controlling an air-fuel ratio in an internal combustion engine having a catalyst converter for removing pollutants in the exhaust gas thereof, an air-fuel ratio sensor disposed downstream of or within said catalyst converter, for detecting a concentration of a specific component in the exhaust gas, and a pull-up type input circuit for supplying a differential current to said air-fuel ratio sensor and receiving an output of said air-fuel ratio sensor, comprising:
- means for comparing the output of said pull-up type input circuit with a first value which is slightly higher than a rich state level of said pull-up input circuit after said engine is warmed-up;
- means for comparing the output of said pull-up type input circuit with a second value higher than said first value;
- means for determining that said downstream-side stream-side air-fuel ratio sensor is in an activation state when the output of said pull-up type input circuit is lower than said first value;
- determining that said downstream-side air-fuel ratio sensor is in a non-activation state when the output of said pull-up type input circuit is higher than said second value,
- means for determining that said downstream-side air-fuel ratio sensor is in a previous state when the output of said pull-up type input circuit is between said first and second values;
- and
- means for adjusting an actual air-fuel ratio in accordance with the output of said downstream-side air-fuel ratio sensor when said air-fuel ratio sensor is in an activation state.
Dependencies are inferred from the claim text.