Air-fuel ratio control system for internal combustion engines

Details Air-fuel ratio control system for internal combustion engines Air-fuel ratio control system for internal combustion engines

1997-09-25

1999-09-07

Argenbright, Tony M.

Internal-combustion engines

Charge forming device

Including exhaust gas condition responsive means

123674, 123679, 701109, F02D 4100

Patent

active

059470968

ABSTRACT:
An air-fuel ratio control system for an internal combustion engine includes an air-fuel ratio sensor for detecting the air-fuel ratio of exhaust gases from the engine. An ECU estimates the air-fuel ratio of a mixture supplied to each of the cylinders cylinder by cylinder in response to an output from the air-fuel ratio sensor, by using an observer based on a model representative of the behavior of the exhaust system. Cylinder-by-cylinder air-fuel ratio control amounts corresponding respectively to the cylinders are calculated for carrying out feedback control of the air-fuel ratio of the mixture such that each of the estimated air-fuel ratio is converged to a desired value. One of the cylinder-by-cylinder air-fuel ratio control amounts corresponding to one of the cylinders is held at a predetermined value, and it is determined whether relationships in value between ones of the cylinder-by-cylinder air-fuel ratio control amounts corresponding respectively to cylinders other than the one cylinder and a plurality of predetermined determination values meet a predetermined determination pattern. When the relationships meet the predetermined determination pattern, it is determined that the response speed of the air-fuel ratio sensor has changed.

REFERENCES:
patent: 5485826 (1996-01-01), Ohata et al.
patent: 5619976 (1997-04-01), Kitagawa et al.
patent: 5657735 (1997-08-01), Maki et al.

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