Engine air/fuel control with adaptive learning
AssigneeFord Motor Company
InventorsDouglas R. Hamburg, Dennis C. Reed, Nicholas G. Zorka
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Abstract
An air/fuel control system for an engine (28) provides an air/fuel indicating signal linearly related to average engine air/fuel operation from a two-state exhaust gas oxygen sensor (44). Fuel delivered to the engine is modulated with a periodic signal (144). Adaptive feedback control (steps 200-280) adaptively learns a desired amplitude for the periodic signal to generate the air/fuel indicating signal with desired sensitivity and operating range.
Claims17
A control method for an engine having an exhaust gas oxygen sensor with a two state output having first and second states respectively corresponding to exhaust gases being rich or lean of stoichiometry, comprising the steps of:
- modulating flow of fuel delivered to the engine with a modulation signal having a preselected peak amplitude;
- providing an air/fuel ratio indicating signal from an average of the sensor output;
- changing said fuel flow a predetermined amount to achieve a preselected offset in engine air/fuel ratio;
- and
- adjusting said modulation signal amplitude in response to a detection of when said air/fuel indicating signal exceeds a preselected value during said fuel flow changing step.
A control method for an engine having an exhaust gas oxygen sensor with a two state output having first and second states receptively corresponding to exhaust gases being rich or lean of stoichiometry, comprising the steps of:
- modulating fuel flow delivered to the engine with a modulation signal having a preselected amplitude;
- averaging the exhaust gas oxygen sensor output to provide an air/fuel indicating signal having an amplitude related to engine air/fuel operation;
- generating an error signal from a difference between said air/fuel indicating signal and a reference signal;
- generating a feedback variable from said error signal;
- correcting said delivered fuel with said feedback variable;
- biasing said modulation signal a predetermined amount to achieve a preselected offset in engine air/fuel ratio;
- and
- adjusting said modulation signal amplitude in response to a detection of when said air/fuel indicating signal exceeds a preselected value during said biasing step.
A control system for an engine, comprising:
- an exhaust gas oxygen sensor with a two state output having first and second states respectively corresponding to exhaust gases being rich or lean of stoichiometry;
- a fuel controller delivering fuel to the engine in response to a desired fuel signal;
- a controller modulating said desired fuel signal with a modulation signal having a preselected amplitude and averaging an output of said exhaust gas oxygen sensor to provide an air/fuel indicating signal having an amplitude related to engine air/fuel operation;
- reference means for providing a reference signal having a first reference value corresponding to an air/fuel ratio lean of stoichiometry during cold engine operation and a second reference value corresponding to a stoichiometric air/fuel ratio during warm engine operation;
- feedback means for integrating an error signal derived from a difference said air/fuel indicating signal and said reference signal to generate a feedback variable, and correcting said delivered fuel with said feedback variable;
- and
- said controller offsetting said delivered fuel a predetermined amount to achieve a preselected rich offset in engine air/fuel ratio, said controller increasing said modulation signal amplitude in response to a detection of when said air/fuel indicating signal exceeds a preselected value during said offsetting step.
Dependencies are inferred from the claim text.