Air/fuel control system for an internal combustion engine
AssigneeFord Motor Company
InventorsDouglas R. Hamburg, Dennis C. Reed
Life of this patent
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Abstract
An air/fuel control system having a feedback variable generated by modulating fuel flow into the engine, generating an error signal from a difference between the average of an exhaust gas oxygen sensor output and a reference value correlated with a desired air/fuel ratio, and integrating the error signal. The reference value is periodically offset in both lean and rich air/fuel directions. A biasing signal is generated from an exhaust gas oxygen sensor position downstream of the converter in response to the air/fuel offset. After removing the offset from the reference value, the bias signal is applied thereto for centering engine air/fuel operation within the peak efficiency window of a catalytic converter.
Claims10
An air/fuel control method for an engine responsive to first and second exhaust gas oxygen sensors positioned in the engine exhaust respectively upstream and downstream of a catalytic converter, comprising the steps of:
- modulating an engine fuel flow signal;
- correcting said fuel flow signal by a feedback variable derived from the first sensor to cause engine air/fuel operation near a desired air/fuel ratio;
- offsetting said fuel flow signal by a first value during a first predetermined time to cause a corresponding rich offset in engine air/fuel operation and offsetting said fuel flow signal during a second predetermined time by a second value to cause a corresponding lean offset in engine air/fuel operation;
- and
- biasing said fuel flow signal with a rich fuel bias when the second sensor indicates excessively lean engine exhaust in response to said lean fuel offset and biasing said fuel flow signal with a lean fuel bias when the second sensor indicates excessively rich exhaust gases in response to said rich fuel offset.
An air/fuel control method for an engine responsive to first and second exhaust gas oxygen sensors positioned in the engine exhaust respectively upstream and downstream of a catalytic converter, comprising the steps of:
- generating a fuel flow signal having an amplitude proportional to an indication of inducted airflow to cause engine air/fuel operation near a desired air/fuel ratio;
- correcting said fuel flow signal by a feedback variable derived from the first sensor;
- modulating said fuel flow signal;
- offsetting said fuel flow signal by a first value during a first predetermined time to cause a corresponding rich offset in engine air/fuel operation and immediately thereafter offsetting said fuel flow signal in a lean air/fuel direction to cancel said rich offset, and offsetting said fuel flow signal during a second predetermined time by a second value to cause a corresponding lean offset in engine air/fuel operation and immediately thereafter offsetting said fuel flow signal in a rich air/fuel direction to cancel said lean offset;
- and
- biasing said fuel flow signal with a rich fuel bias when the second sensor indicates excessively lean engine exhaust in response to said lean fuel offset and biasing said fuel flow signal with a lean fuel bias when the second sensor indicates excessively rich exhaust gases in response to said rich fuel offset.
Dependencies are inferred from the claim text.