Device for determining deterioration of air-fuel ratio sensor

Details Device for determining deterioration of air-fuel ratio sensor Device for determining deterioration of air-fuel ratio sensor

1997-07-29

1999-05-11

Kwon, John T.

Internal-combustion engines

Charge forming device

Including exhaust gas condition responsive means

73 2332, 123690, F02M25/00

Patent

active

059016914

ABSTRACT:
A device for determining deterioration of an air-fuel ratio sensor according to the present invention includes: an air-fuel ratio sensor provided in an exhaust passage of an internal combustion engine, the air-fuel ratio sensor being capable of continuously detecting a broad range of air-fuel ratios including a stoichiometric air-fuel ratio; an air-fuel ratio feedback control circuit for feedback controlling a fuel injection amount based on a difference between an output of the air-fuel ratio sensor and a target output corresponding to a target air-fuel ratio so that an air-fuel ratio of a gaseous mixture substantially equals the target air-fuel ratio, the gaseous mixture being supplied to the engine; a variation cumulative value calculation circuit for cumulating, while the air-fuel ratio feedback control is being performed by the air-fuel ratio feedback control circuit, a variation .DELTA.FT in a fuel injection correction amount, thereby calculating a cumulative variation value .SIGMA..DELTA.FT for a predetermined period; and a deterioration determination circuit for determining that the air-fuel ratio sensor is deteriorated when the cumulative variation value .SIGMA..DELTA.FT calculated by the variation cumulative value calculation circuit exceeds a predetermined value.

REFERENCES:
patent: 5485382 (1996-01-01), Seki et al.
patent: 5724952 (1998-03-01), Miyashita et al.
patent: 5724953 (1998-03-01), Jung
patent: 5758632 (1998-06-01), Yamashita et al.
patent: 5769063 (1998-06-01), Mizusawa

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