Engine air/fuel control with adaptive correction of ego sensor output
AssigneeFord Motor Company
InventorsDouglas R. Hamburg, Eleftherios M. Logothetis
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Abstract
Engine air/fuel ratio is controlled in response to a comparison of an exhaust gas oxygen sensor output with a reference value. A correction voltage is generated which is related to a change in the midpoint between saturated output states of the sensor during a test period in which engine air/fuel operation is first forced rich and then forced lean of a preselected air/fuel ratio. The sensor output amplitude is shifted with the correction voltage to reduce variations between the reference value and the midpoint.
Claims16
An engine air/fuel control method for correcting an output of an exhaust gas oxygen sensor positioned in the engine exhaust in series with a catalytic converter, comprising the steps of:
- controlling the engine air/fuel ratio in response to a comparison of the sensor output with a reference value;
- forcing engine air/fuel operation sufficiently rich and then sufficiently lean of a preselected air/fuel ratio during a test period to force the sensor output into its respective saturated rich indicating state and saturated lean indicating state;
- and
- shifting the sensor output to align a midpoint between output amplitude at said saturated rich indicating state and output amplitude at said saturated lean indicating state with said reference value.
An engine air/fuel control method for correcting an output of an exhaust gas oxygen sensor positioned in the engine exhaust in series with a catalytic converter, comprising the steps of:
- controlling the engine air/fuel ratio in response to a comparison of the sensor output with a reference value;
- generating a correction voltage during a test period in which engine air/fuel operation is first forced sufficiently rich and then forced sufficiently lean of stoichiometry for preselected time periods to force the sensor output into its respective saturated rich indicating state and saturated lean indicating state, said correction voltage being generated by subtracting said reference from a value related to both amplitude in the sensor output at said saturated rich indicating state and the sensor output amplitude at said saturated lean indicating state;
- correcting said sensor output with said correction voltage;
- and
- indicating sensor stability in response to an average of said correction voltages over a preselected number of test periods.
An engine air/fuel control method for correcting an output of an exhaust gas oxygen sensor positioned in an engine exhaust upstream of a catalytic converter, comprising the steps of:
- generating an error signal related to a difference between a signal derived from an exhaust gas oxygen sensor positioned downstream of the converter and a predetermined value;
- feedback control of the engine air/fuel ratio in response to a feedback variable derived by integrating a difference between the upstream sensor output and a reference value, said feedback control also being responsive to said error signal;
- disabling said feedback control during a test period;
- forcing engine air/fuel operation sufficiently rich and then sufficiently lean of a preselected air/fuel ratio during a test period to force the sensor output into its respective saturated rich indicating state and saturated lean indicating state;
- determining a voltage shift related to a difference between said reference and a midpoint between the sensor output amplitude at said saturated rich indicating state and said saturated lean indicating state;
- generating a correction ratio of said voltage shift to a stored value related to engine operating conditions during said test period;
- correcting said upstream sensor output with a correction voltage derived by multiplying said correction ratio times an estimated correction derived from engine operating conditions;
- and
- indicating sensor stability by averaging said correction voltages over a preselected number of test periods and comparing an absolute difference between said correction voltage and said average correction voltage to a preselected reference during said test period.
Dependencies are inferred from the claim text.