Feedback control system

• US 5,341,643 A
• Filed: 04/05/1993
• Issued: 08/30/1994
• Est. Priority Date: 04/05/1993
• Status: Expired due to Fees

• Current Assignee: Ford Global Technologies, LLC (Ford Motor Company)
• Original Assignee: Ford Motor Company
• Inventors: Soltis, Richard E., Visser, Jacobus H., Logothetis, Eleftherios M., Hamburg, Douglas R.
• Primary Examiner(s): Hart, Douglas
• Application Number:
  US08/043,095
• Time in Patent Office: 512 Days
• Field of Search: 60/274, 60/276, 60/277, 60/285, 123/691, 123/688
• US Class Current: 60/276
• CPC Class Codes: F02D 41/1441 Plural sensors

Abstract

An air/fuel control system which includes feedback control from an exhaust gas oxygen sensor positioned upstream of a catalytic converter. The exact air/fuel ratio required optimum converter efficiency is determined by generating an emissions signal from both a HC/CO sensor and a NO sensor each positioned downstream of the catalytic converter. The feedback variable is trimmed by a signal derived from the emissions signal to maintain air/fuel operation at a value corresponding to maximum converter efficiency.

Claims

1. An engine air/fuel control method for optimizing conversion efficiency of a catalytic converter positioned in the engine exhaust, comprising the steps of:

measuring nitrogen oxide content of exhaust gases downstream of the catalytic converter to generate a first measurement signal;

measuring combined hydrocarbon and carbon monoxide content in exhaust gases downstream of the catalytic converter to generate a second measurement signal;

subtracting said first measurement signal from said second measurement signal to generate a third signal;

generating a correction signal from an exhaust gas oxygen sensor positioned upstream of the catalytic converter;

trimming said correction signal with a trim signal derived from said third signal and then integrating to generate a feedback variable; and

correcting fuel delivered to the engine by said feedback variable to maintain maximum conversion efficiency of the catalytic converter.

2. The engine air/fuel control method recited in claim 1 further comprising the step of integrating said third signal to derive said trim signal.

3. The engine air/fuel control method recited in claim 2 further comprising the step of multiplying said third signal by a proportional term and adding the resulting product to said integration of said third signal to derive said trim signal.

4. An engine air/fuel control method for optimizing conversion efficiency of a catalytic converter positioned in the engine exhaust, comprising the steps of:

measuring nitrogen oxide content of exhaust gases downstream of the catalytic converter and normalizing said measurement with respect to at least engine speed to generate a first measurement signal;

measuring combined hydrocarbon and carbon monoxide content in exhaust gases downstream of the catalytic converter and normalizing said measurement with respect to at least engine speed to generate a second measurement signal;

subtracting said first measurement signal from said second measurement signal to generate a trim signal;

generating a correction signal from an exhaust gas oxygen sensor positioned upstream of the catalytic converter;

trimming said correction signal with said trim signal and then integrating to generate a feedback variable;

delivering fuel to the engine in response to an indication of airflow inducted into the engine and a reference air/fuel ratio; and

correcting said delivered fuel by said feedback variable to maintain maximum conversion efficiency of the catalytic converter.

5. The engine air/fuel control method recited in claim 4 wherein said trim signal is derived by integrating said emissions indicating signal and adding a product of a gain value times said emissions indicating signal to the resulting integration.

6. The engine air/fuel control method recited in claim 4 wherein said step of generating a correction signal further comprises a step of comparing said exhaust gas oxygen sensor output to a reference value such that said correction signal has a predetermined amplitude with a first polarity when exhaust gases are rich of a preselected air/fuel ratio and a second polarity opposite said first polarity when said exhaust gases are lean of said preselected air/fuel ratio.

7. An engine control system for optimizing conversion efficiency of a catalytic converter positioned in the engine exhaust, comprising:

a first sensor positioned downstream of the catalytic converter for providing a first electrical signal having an amplitude related to quantity of nitrogen oxides in the exhaust;

a second sensor positioned downstream of the catalytic converter for providing a second electrical signal having an amplitude related to quantity of at least one exhaust by-product other than nitrogen oxides, said second electrical signal is related to quantity of carbon monoxide in the engine exhaust;

an exhaust gas oxygen sensor positioned upstream of the catalytic converter for providing a feedback signal related to oxygen content of the exhaust gases;

correction means for combining said first and said second electrical signals to generate a trim signal related to maximum converter efficiency of the catalytic converter and for correcting said feedback signal with said trim signal; and

fuel control means for delivering fuel to the engine in relation to quantity of air inducted into the engine and a desired air/fuel ratio and said corrected feedback variable.

8. An engine control system for optimizing conversion efficiency of a catalytic converter positioned in the engine exhaust, comprising:

a first sensor positioned downstream of the catalytic converter for providing a first electrical signal having an amplitude related to quantity of nitrogen oxides in the exhaust;

a second sensor positioned downstream of the catalytic converter for providing a second electrical signal having an amplitude related to quantity of at least one exhaust by-product other than nitrogen oxides, said second electrical signal is related to quantity of hydrocarbons in the engine exhaust;

an exhaust gas oxygen sensor positioned upstream of the catalytic converter for providing a feedback signal related to oxygen content of the exhaust gases;

correction means for combining said first and said second electrical signals to generate a trim signal related to maximum converter efficiency of the catalytic converter and for correcting said feedback signal with said trim signal; and

fuel control means for delivering fuel to the engine in relation to quantity of air inducted into the engine and a desired air/fuel ratio and said corrected feedback variable.