Air/fuel control with adaptively learned reference
First Claim
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1. An air/fuel control method for an internal combustion engine, comprising the steps of:
- adjusting fuel delivered to the engine in response to a comparison of an output from an exhaust gas oxygen sensor to an adaptively learned reference signal;
generating said adaptively learned reference signal by determining a linear interpolation between a first signal and a second signal; and
generating said first signal by storing said sensor signal as said first signal when said sensor signal is greater than a previously stored first signal and holding said first signal when said sensor signal is less than a previously stored reference signal and decreasing said first signal at a predetermined rate when said sensor signal is greater than said previously stored reference signal but less than said previously stored first signal.
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Abstract
An engine air/fuel control system includes an apparatus and method for adaptively learning a reference voltage. Fuel delivered to the engine is trimmed by a feedback variable provided by integrating a two-state signal resulting from a comparison between the reference voltage and the exhaust gas oxygen sensor output. Each sample period of a microprocessor, a high voltage signal and low voltage signal are generated which track the outer envelope of the sensor signal. Calculation of a midpoint between high and low voltage signals provides the reference which instantaneously tracks the midpoint of the sensor signal.
32 Citations
13 Claims
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1. An air/fuel control method for an internal combustion engine, comprising the steps of:
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adjusting fuel delivered to the engine in response to a comparison of an output from an exhaust gas oxygen sensor to an adaptively learned reference signal; generating said adaptively learned reference signal by determining a linear interpolation between a first signal and a second signal; and generating said first signal by storing said sensor signal as said first signal when said sensor signal is greater than a previously stored first signal and holding said first signal when said sensor signal is less than a previously stored reference signal and decreasing said first signal at a predetermined rate when said sensor signal is greater than said previously stored reference signal but less than said previously stored first signal. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8)
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9. An air/fuel control method for an internal combustion engine, comprising the steps of:
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maintaining an air/fuel mixture inducted into the engine near a desired air/fuel ratio in response to a comparison of an output from an exhaust gas oxygen sensor to an adaptively learned reference signal; adaptively learning 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; during each of said sample times generating said first signal 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 holding said first signal when said sensor signal is less than said reference 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; and during each of said sample times generating said second signal 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 holding said second signal when said sensor signal is greater than said reference signal from the previous sample time and increasing said first signal by a predetermined amount when said sensor signal is less than said previously sampled reference signal but greater than said previously sampled first signal. - View Dependent Claims (10, 11)
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12. 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; 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 holding said first signal when said sensor signal is less than said reference 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; and 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 holding said second signal when said sensor signal is greater than said reference signal from the previous sample time and increasing said first signal by a predetermined amount when said sensor signal is less than said previously sampled reference signal but greater than said previously sampled first signal. - View Dependent Claims (13)
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Specification