Air/fuel control method with adaptive feedback actuation
First Claim
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1. An engine air/fuel control method responsive to an output from an exhaust gas sensor, comprising the steps of:
- modulating fuel delivered to the engine during an initialization period;
terminating said initialization period when a difference between high and low excursion in the sensor output exceeds a preselected value; and
adjusting fuel delivered to the engine in response to a feedback variable derived from the sensor output, said adjusting step being initiated in response to said termination of said initialization period.
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Abstract
An engine air/fuel control system includes an apparatus and method for adaptively setting an initialization period preceding closed loop fuel control. During the initialization period, fuel delivered to the engine is modulated by a periodic waveform. A high voltage signal associated with the high output state of an exhaust gas oxygen sensor and a low voltage signal associated with the low voltage state of the exhaust gas oxygen sensor are sampled. When the difference between these signals exceeds a preselected value, the initialization period is terminated and closed loop fuel control is actuated.
13 Citations
17 Claims
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1. An engine air/fuel control method responsive to an output from an exhaust gas sensor, comprising the steps of:
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modulating fuel delivered to the engine during an initialization period; terminating said initialization period when a difference between high and low excursion in the sensor output exceeds a preselected value; and adjusting fuel delivered to the engine in response to a feedback variable derived from the sensor output, said adjusting step being initiated in response to said termination of said initialization period. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10)
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11. An engine air/fuel control method responsive to an output from an exhaust gas sensor, comprising the steps of:
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modulating fuel delivered to the engine during an initialization period; generating a first signal by storing the sensor output as said first signal while the sensor output is greater than a previously stored first signal and decreasing said previously stored first signal at a predetermined rate while the sensor output is less than said previously stored first signal; generating a second signal by storing the sensor output as said second signal while the sensor output is less than a previously stored second signal and increasing said previously stored second signal at a predetermined rate while the sensor output is greater than said previously stored second signal; terminating said initialization period when a difference between said first signal and said second signal exceeds a preselected value; and adjusting fuel delivered to the engine in response to a feedback variable derived from the sensor output, said adjusting step being initiated in response to said termination of said initialization period. - View Dependent Claims (12, 13, 14)
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15. An air/fuel control system for an internal combustion engine, comprising:
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a controller maintaining an air/fuel mixture inducted into the engine near a desired air/fuel ratio in response to a feedback variable after an initialization period; feedback means for generating said feedback variable by integrating a two-state signal generated by comparing an output from an exhaust gas oxygen sensor to an adaptively learned reference signal; adaptive learning means for providing said reference signal by determining a midpoint between a first signal and a second signal during each of a repetitively occurring number of sample times; first signal generating means for generating said first signal each of said sample times by storing said sensor signal as said first signal when said sensor signal is greater than said first signal from the previous sample time and decreasing said first signal by a predetermined amount when said sensor signal is greater than said previously sampled reference signal but less than said previously sampled first signal; second signal generating means for generating said second signal each of said sample times by storing said sensor signal as said second signal when said sensor signal is less than said second signal from the previous sample time and increasing said second signal by a predetermined amount when said sensor signal is less than said previously sampled reference signal but greater than said previously sampled second signal; modulation means for modulating fuel delivered to the engine during said initialization period; and initialization means for generating said initialization period in response to an indication of at least one engine operating parameter exceeding a preselected value and terminating said initialization period when a difference between said first signal and said second signal exceeds a preselected value. - View Dependent Claims (16, 17)
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Specification