Engine with dual sensor closed loop fuel control

• US 3,939,654 A
• Filed: 02/11/1975
• Issued: 02/24/1976
• Est. Priority Date: 02/11/1975
• Status: Expired due to Term

• Current Assignee: General Motors Corporation (General Motors Company)
• Original Assignee: General Motors Corporation (General Motors Company)
• Inventors: Creps, Wendell D.
• Primary Examiner(s): Hart, Douglas
• Application Number:
  US05/548,969
• Time in Patent Office: 378 Days
• Field of Search: 60/276, 60/285, 60/286
• US Class Current: 60/276
• CPC Class Codes: F01N 11/00 Monitoring or diagnostic devices for exhaust-gas treatment apparatus , e.g. for catalytic activity safety, indicating or supervising devices for internal combustion engines F02B77/08; testing of machines G01M13/00
• CPC Class Codes: F01N 2430/06 by varying fuel-air ratio, e.g. by enriching fuel-air mixture
• CPC Class Codes: F01N 9/00 Electrical control of exhaust gas treating apparatus monitoring or diagnostic devices for exhaust-gas treatment apparatus F01N11/00; conjoint electrical control of two or more combustion engine functions F02D43/00
• CPC Class Codes: F02D 41/1441 Plural sensors
• CPC Class Codes: F02M 7/20 operated automatically, e.g. dependent on altitude
• CPC Class Codes: Y02T 10/40 Engine management systems
• CPC Class Codes: Y10S 261/74 Valve actuation; electrical

Abstract

In a closed loop fuel control system for an internal combustion engine having a catalytic converter in its exhaust system, a first zirconia sensor in the exhaust system upstream from the catalytic converter generates a signal indicative of air-fuel ratio in gases before catalytic treatment, a second zirconia sensor in the exhaust system downstream from the catalytic converter generates a signal indicative of air-fuel ratio in gases after catalytic treatment and a cascade feedback control system including both zirconia sensors controls the rate of flow of fuel or air to the engine in response to both sensor signals and a reference to maintain a constant stoichiometric air-fuel ratio in the exhaust system for maximum catalytic converter efficiency in simultaneous oxidation and reduction. The engine fuel system reverts to open loop operation during wide open throttle, closed throttle and cold start operation.

Claims

1. For use with an internal combustion engine including means for supplying air and fuel thereto in variable ratio and exhaust means including a catalytic converter effective, when supplied with exhaust gases containing air and fuel in a certain ratio, to accelerate simultaneously the oxidation of unburned fuel and the reduction of nitrogen oxides and characterized by time delay effects when the content of the gas introduced therein is varied, apparatus for controlling the ratio of air and fuel in said exhaust system to said certain ratio, said apparatus comprising:

means for generating a first signal indicative of the air-fuel ratio within said exhaust means upstream from said catalytic converter, said first signal generating means being characterized by time-related drift in closed cycle control operation;

means for generating a second signal indicative of the air-fuel ratio within said exhaust means downstream from said catalytic converter, said second signal generating means being characterized by catalytic converter-related, time-delayed response in relation to said first signal generating means; and

means for continually adjusting said fuel and air supply means to vary the ratio of fuel and air supplied to said engine in response to the direction of the deviation of said first signal from the time integral of the extent the second signal deviates from a fixed reference, said adjustment being in sense to reduce the deviation of the ratio of fuel and air in the exhaust means from said certain ratio.

2. For use with an internal combustion engine including means for supplying air and fuel thereto in variable ratio and exhaust means including a catalytic converter effective, when supplied with exhaust gases containing air and fuel in a certain ratio, to accelerate simultaneously the oxidation of unburned fuel and the reduction of nitrogen oxides and characterized by time delay effects when the content of the gas introduced therein is varied, apparatus for controlling the ratio of air and fuel in said exhaust system to said certain ratio, said apparatus comprising:

means for generating a first signal indicative of the air-fuel ratio within said exhaust means upstream from said catalytic converter, said first signal generating means being characterized by time-related drift in closed cycle control operation;

means for generating a second signal indicative of the air-fuel ratio within said exhaust means downstream from said catalytic converter, said second signal generating means being characterized by catalytic converter-related time-delayed response in relation to said first signal generating means;

means responsive to the second signal to generate a third signal varying with the time integral of said second signal;

means responsive to the first and third signal to generate a fourth signal having one value when the first signal exceeds the third signal and another value when a third signal exceeds the first signal; and

means responsive to the fourth signal to continuously adjust the ratio of air and fuel supplied to the engine in a direction to reduce the difference between the ratio of air and fuel in the exhaust means and said certain ratio.

3. For use with an internal combustion engine including means for supplying air and fuel thereto in variable ratio and exhaust means including a catalytic converter effective, when supplied with exhaust gases containing air and fuel in a certain ratio, to accelerate simultaneously the oxidation of unburned fuel and the reduction of nitrogen oxides and characterized by time delay effects when the content of the gas introduced therein is varied, apparatus for controlling the ratio of air and fuel in said exhaust system to said certain ratio, said apparatus comprising:

means for generating a first signal indicative of the air-fuel ratio within said exhaust means upstream from said catalytic converter, said first signal generating means being characterized by time-related drift in closed cycle control operation;

means for generating a second signal indicative of the air-fuel ratio within said exhaust means downstream from said catalytic converter, said second signal generating means being characterized by catalytic converter-related time-delayed response in relation to said first signal generating means;

a first integrator responsive to the second signal and effective to generate a third signal varying with the time integral of the second signal;

a comparator responsive to the first and third signals and effective to generate a fourth signal having a first value when the first signal exceeds the third signal and a second value when a third signal exceeds the first signal;

a second integrator responsive to the fourth signal and effective to generate a fifth signal varying as the time integral of the fourth signal; and

means responsive to the fifth signal for continuously adjusting the ratio of air and fuel supplied to the engine in extent and direction to reduce the deviation between the ratio of air and fuel in the exhaust means as sensed by either sensor and said certain ratio.

4. For use with an internal combustion engine including means for supplying air and fuel thereto in variable ratio and exhaust means including a catalytic converter effective, when supplied with exhaust gases containing air and fuel in a certain ratio, to accelerate simultaneously the oxidation of unburned fuel and the reduction of nitrogen oxides and characterized by time delay effects when the content of the gas introduced therein is varied, apparatus for controlling the ratio of air and fuel in said exhaust system to said certain ratio, said apparatus comprising:

a first zirconia sensor effective to generate a first signal indicative of the deviation of the air-fuel ratio from said certain ratio within said exhaust means upstream from said catalytic converter, said first zirconia sensor being characterized by time-rated drift in closed loop control operation;

a second zirconia sensor effective to generate a second signal indicative of the deviation of the air-fuel ratio from said certain ratio with said exhaust means downstream from said catalytic converter, said second zirconia sensor being characterized by catalytic converter-related, time-delayed response in relation to said first signal generating means;

a first integrator responsive to the second signal and effective to generate a third signal varying with the time integral of the second signal;

a comparator responsive to the first and third signals and effective to generate a fourth signal having a first value when the first signal exceeds the third signal and a second value when a third signal exceeds the first signal;

a second integrator responsive to the fourth signal and effective to integrate with respect to time at a constant rate in one direction when the fourth signal has its first value and in the other direction when the fourth signal has its second value and produce thereby a fifth signal;

means responsive to the first signal to generate a sixth signal varying with the first signal and having phase lead with respect to said fifth signal; and

means responsive to the fifth and sixth signals to continuously adjust the ratio of air and fuel supplied to the engine in extent and direction to reduce the difference between the air-fuel ratio of gases in the exhaust means and the certain ratio.

5. A power plant for a vehicle comprising, in combination:

a combustion engine;

means for supplying air and fuel to the engine in variable ratio;

means for conducting exhaust gases from the engine, said means including a catalytic converter effective, when supplied with exhaust gases containing air and fuel in a certain ratio, to simultaneously oxidize hydrocarbons and carbon monoxide and reduce oxides of nitrogen, the catalytic converter further being effective, when the exhaust gases supplied thereto exhibit a change in air-fuel ratio, to delay the appearance of a corresponding change in the gases emitted therefrom;

a first sensor in the exhaust conduit between the engine and catalytic converter, the first sensor generating a first signal varying inversely with air-fuel ratio of the exhaust gases emitted from the engine, said first signal being characterized by time and temperature related drift;

a second sensor in the exhaust conduit on the far side of the catalytic converter from the engine, the second sensor generating a second signal varying inversely with the air-fuel ratio of the exhaust gases emitted from the catalytic converter;

said second signal being characterized by catalytic converter-related delayed response, compared with the first signal, to changes in exhaust gas air-fuel ratio;

a first integrator responsive to the second signal and effective to generate an output signal varying with the time integral thereof;

a comparator responsive to the first signal and the first integrator output signal and effective to generate an output signal having a fixed absolute value with a first sign when the first signal exceeds the first integrator output signal and a second sign when the first integrator output signal exceeds the first signal;

a second integrator responsive to the comparator output signal to generate an output signal varying with the time integral of the comparator output signal;

a proportional amplifier responsive to the first signal and effective to generate an output signal varying directly with the first signal;

means responsive to the sum of the second integrator output signal and the proportional amplifier output signal to control the air-fuel supply means and vary the ratio of air and fuel supplied to the engine in extent and direction to simultaneously reduce the deviations from said certain ratio of the air-fuel ratio of gases in the exhaust conduit both supplied to and emitted from the catalytic converter.

6. For use with a combustion engine including means for supplying air and fuel and exhaust means for transporting exhaust gases containing oxidizing and reducing agents in ratio determined by said supply means, said exhaust means including a catalytic converter effective, when supplied with exhaust gases containing oxidizing and reducing agents in a certain ratio, to accelerate certain reactions between said oxidizing and reducing agents and characterized by time delay effects when the content of the exhaust gases supplied thereto is varied, apparatus for controlling the ratio of oxidizing and reducing agents in said exhaust means to said certain ratio, said apparatus comprising:

means for generating a first signal indicative of the portion of one of said agents in said exhaust means upstream from said catalytic converter, said first signal generating means being characterized by time-related drift in closed cycle control operation;

means for generating a second signal indicative of the portion of said one agent in said exhaust means downstream from said catalytic converter, said second signal generating means being characterized by catalytic converter-related, time-delayed response in relation to said first signal generating means; and

means for continually adjusting said fuel and air supply means to vary the ratio of oxidizing and reducing agents in said exhaust gases in response to the direction of the deviation of said first signal from the time integral of the extent the second signal deviates from a fixed reference, said adjustment being in sense to reduce the deviation of the ratio of oxidizing and reducing agents in the exhaust means from said certain ratio.