Power plants – Internal combustion engine with treatment or handling of... – Having means analyzing composition of exhaust gas
Reexamination Certificate
1998-09-09
2001-01-23
Denion, Thomas (Department: 3748)
Power plants
Internal combustion engine with treatment or handling of...
Having means analyzing composition of exhaust gas
C060S277000, C060S274000, C073S118040, C073S023310, C073S023320, C123S688000
Reexamination Certificate
active
06176080
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to an oxygen concentration sensor abnormality-detecting system for internal combustion engines, which detects abnormality of an oxygen concentration sensor arranged in the exhaust system of the engine at a location upstream of a catalytic converter arranged therein.
2. Prior Art
To detect abnormality of an oxygen concentration sensor arranged in the exhaust system of an internal combustion engine at a location upstream of a catalytic converter arranged therein, an oxygen concentration sensor abnormality-detecting system has been proposed by Japanese Utility Model Publication (Kokoku) No. 62-28675, which determines that the oxygen concentration sensor is abnormal if the output level of the oxygen concentration sensor remains less than a predetermined value, i.e. stays on a lean side when an increased amount of fuel is supplied to the engine.
According to this abnormality-detecting system, however, the detection of abnormality of the oxygen concentration sensor has to be carried out only when the amount of fuel supplied to the engine is increased. On the other hand, from the standpoint of fuel economy, it is required that the frequency of increase of the fuel amount supplied to the engine should be as low as possible. Consequently, the detection of abnormality of the oxygen concentration sensor cannot be carried out so long as no increase of the fuel amount supplied to the engine is required, resulting in a very low frequency of execution of the abnormality detection.
Further, a gas engine in particular undergoes large variations in the air-fuel ratio of a mixture supplied to the engine due to variations in the composition of the fuel such that the air-fuel ratio of the mixture cannot be surely enriched even when the fuel supply amount is controlled to an increased amount, which can result in an erroneous detection of abnormality of the oxygen concentration sensor.
SUMMARY OF THE INVENTION
It is an object of the invention to provide an oxygen concentration sensor abnormality-detecting system for internal combustion engines, which is capable of detecting abnormality of an oxygen concentration sensor upstream of a catalytic converter without the detection timing being limited to occasions of increase of the fuel amount supplied to the engine.
Another object of the invention is to accurately detect abnormality of an oxygen concentration sensor upstream of a catalytic converter without erroneous detection.
To attain the above objects, the present invention provides an oxygen concentration sensor abnormality-detecting system for an internal combustion engine having an exhaust system, a catalytic converter arranged in the exhaust system, first and second oxygen concentration sensors arranged in the exhaust system at respective locations upstream and downstream of the catalytic converter, comprising abnormality-determining means for determining that the first oxygen concentration sensor is functioning abnormally if an output from the first oxygen concentration sensor does not change when an output from the second oxygen concentration sensor changes.
According to the above manner of abnormality detection, it is possible to detect abnormality of the first oxygen concentration sensor upstream of the catalytic converter without the detection timing being limited to occasions of increase of the fuel amount supplied to the engine, as well as largely reduce the possibility of erroneous detection as to abnormality of the first oxygen concentration sensor.
Preferably, the abnormality-determining means determines that the first oxygen concentration sensor is functioning abnormally if the output from the first oxygen concentration sensor stays in a direction such that an air-fuel ratio of a mixture supplied to the engine is leaner than a stoichiometric air-fuel ratio when the output from the second oxygen concentration sensor has changed in a direction such that the air-fuel ratio of the mixture is richer than the stoichiometric air-fuel ratio.
More preferably, the abnormality-determining means determines that the first oxygen concentration sensor is functioning abnormally if the output from the first oxygen concentration sensor has continued to indicate that an air-fuel ratio of a mixture supplied to the engine is leaner than a stoichiometric air-fuel ratio, over a predetermined time period when the output from the second oxygen concentration sensor indicates that the air-fuel ratio of the mixture is richer than the stoichiometric air-fuel ratio.
According to the above manner of abnormality detection, erroneous detection of abnormality of the first oxygen concentration sensor can be avoided even in the case where the air-fuel ratio cannot be positively made rich.
The above and other objects, features, and advantages of the invention will become more apparent from the following detailed description taken in conjunction with the accompanying drawings.
REFERENCES:
patent: 5154054 (1992-10-01), Nakane et al.
patent: 5331808 (1994-07-01), Koike
patent: 5363091 (1994-11-01), Kotwicki et al.
patent: 5365216 (1994-11-01), Kotwicki et al.
patent: 5396766 (1995-03-01), Sato et al.
patent: 5485382 (1996-01-01), Seki et al.
patent: 5513522 (1996-05-01), Seki et al.
patent: 5568725 (1996-10-01), Uchikawa
patent: 5577488 (1996-11-01), Sato
patent: 5610321 (1997-03-01), Shinmoto
patent: 5845489 (1998-12-01), Dohta et al.
patent: 62-28675 (1987-07-01), None
Hidai Shigeo
Hosogai Seiichi
Izumiura Atsushi
Kitaura Hirohisa
Murakami Akira
Arent Fox Kintner & Plotkin & Kahn, PLLC
Denion Thomas
Honda Giken Kogyo Kabushiki Kaisha
Trieu Thai-Ba
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