Air/fuel control with adaptively learned reference

Claim 2

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.

Claim 3

The air/fuel control method recited in claim 1 further comprising the step of generating said second signal by storing said sensor signal as said second signal when said sensor signal is less than a previously stored second signal and holding said second signal when said sensor signal is greater than a previously stored reference signal and increasing said second signal at a predetermined rate when said sensor signal is less than said previously stored reference signal but greater than said previously stored second signal.

Claim 4

The air/fuel control method recited in claim 1 wherein said comparison step generates a two-state signal having a first state indicating exhaust gases are rich of stoichiometry and a second state indicating exhaust gases are lean of stoichiometry.

Claim 5

The air/fuel control method recited in claim 3 wherein said fuel adjusting step trims an open loop calculation of desired fuel to be delivered to the engine by a feedback variable generated by integrating said two-state signal.

Claim 6

The air/fuel control method recited in claim 4 wherein said open loop calculation comprises the step of dividing a measurement of airflow inducted into the engine by a desired air/fuel ratio.

Claim 7

The air/fuel control method recited in claim 5 wherein said step of trimming said open loop calculation comprises the step of dividing said open loop calculation by said feedback variable.

Claim 8

The air/fuel control method recited in claim 1 wherein said adjusting step is activated when preselected engine operating conditions exceed preselected values.

Claim 9

The air/fuel control method recited in claim 1 wherein said linear interpolation comprises a midpoint determination.

Claim 10

An air/fuel control method for an internal combustion engine, comprising the steps of: 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.

Claim 11

An air/fuel control method for an internal combustion engine, comprising the steps of: 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.

Claim 12

The air/fuel control method recited in claim 9 wherein said comparison step generates a two-state signal having a first state indicating exhaust gases are rich of stoichiometry and a second state indicating exhaust gases are lean of stoichiometry.

Claim 13

The air/fuel control method recited in claim 10 wherein said step of maintaining engine air/fuel ratio trims an open loop calculation of desired fuel to be delivered to the engine by a feedback variable generated by integrating said two-state signal.

Claim 14

An air/fuel control system for an internal combustion engine, comprising: 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.

Claim 15

An air/fuel control system for an internal combustion engine, comprising: 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.

Claim 16

The system recited in claim 12 wherein said controller provides desired fuel quantity for delivery to the engine by dividing a measurement of airflow inducted into the engine by both a desired air/fuel ratio and said feedback variable.