Power plants – Internal combustion engine with treatment or handling of... – Having sensor or indicator of malfunction – unsafeness – or...
Reexamination Certificate
2001-07-02
2002-07-30
Denion, Thomas (Department: 3748)
Power plants
Internal combustion engine with treatment or handling of...
Having sensor or indicator of malfunction, unsafeness, or...
C060S274000, C060S276000
Reexamination Certificate
active
06425242
ABSTRACT:
TECHNICAL FIELD
The present invention is directed to a system for monitoring catalyst operation in an internal combustion engine having a two-bank exhaust system. More particularly, the invention is directed to a diagnostic system that monitors catalyst efficiency by comparing signals between a pre-catalyst EGO sensor and a post-catalyst EGO sensor in two different banks.
BACKGROUND ART
To meet current emission regulations, automotive vehicles must regulate the air/fuel ratio (A/F) supplied to the vehicles' cylinders so as to achieve maximum efficiency of the vehicles' catalysts. For this purpose, it is known to control the air/fuel ratio of internal combustion engines using an exhaust gas oxygen (EGO) sensor positioned in the exhaust stream from the engine. The EGO sensor provides feedback data to an electronic controller that calculates preferred A/F values over time to achieve optimum efficiency of a catalyst in the exhaust system. More particularly, the EGO sensor feedback signals are used to calculate desired A/F ratios via a jumpback and ramp process, which is known in the art.
It is also known to have systems with two EGO sensors in a single exhaust stream in an effort to achieve more precise A/F control with respect to the catalyst window. Normally, a pre-catalyst EGO sensor is positioned upstream of the catalyst and a post-catalyst EGO sensor is positioned downstream of the catalyst. Finally, in connection with engines having two groups of cylinders, it is known to have a two-bank exhaust system coupled thereto where each exhaust bank has its own catalyst as well as its own pre-catalyst and post-catalyst EGO sensors.
It is known in the art to monitor the efficiency of a catalyst by determining the arc length ratio between signals generated by corresponding pre-catalyst and post-catalyst EGO sensors in the same exhaust stream and connected to the same catalyst. This type of system is described in U.S. Pat. No. 5,899,062 to Jerger et al. and entitled “Catalyst Monitor Using Arc Length Ratio of Pre- and Post-Catalyst Signals”, the disclosure of which is incorporated herein by reference.
Sometimes, in a two-bank, four-EGO sensor exhaust system, one of the pre-catalyst EGO sensors degrades. In other circumstances, it is desirable to purposely eliminate one of the pre-catalyst EGO sensors in a two-bank system to reduce the cost of the system. In either event, it is desirable to be able to monitor the catalyst efficiency in the group of cylinders coupled to the exhaust bank having only one operational EGO sensor by using the signals received from the three operational EGO sensors alone. However, known methods for catalyst diagnosis require a matched set of pre-catalyst and post-catalyst EGO sensors in each bank, such as in a one-bank, two EGO sensor system or in a two-bank, four EGO sensor system, so that the arc lengths between the corresponding pre-catalyst and post-catalyst sensors can be compared. Thus, for a two-bank, three EGO sensor system, only the catalyst in the two EGO sensor exhaust bank will be monitored and diagnosed, while the catalyst in the bank having only one operational EGO sensor will remain unmonitored.
There is a need for an improved system that can monitor the operation of a catalyst in a one-sensor bank even though the catalyst only has one EGO sensor coupled to it.
SUMMARY OF THE INVENTION
Accordingly, the present invention is directed toward a new system and method for monitoring the operation of both catalysts in an internal combustion engine having a group of cylinders coupled to two functioning EGO sensors (the “two-sensor bank”) and another group of cylinders coupled to one functioning EGO sensor (the “one-sensor bank”). More particularly, the operation of the catalyst in the one-sensor bank is monitored and diagnosed based on a signal from a post-catalyst EGO sensor connected to the catalyst and a signal from a pre-catalyst EGO sensor in a different bank and connected to a different catalyst.
In a preferred embodiment of the invention, for a system that is a missing a pre-catalyst EGO sensor in the one-sensor bank, the signal from the pre-catalyst EGO sensor in the two-sensor bank is used to calculate a diagnostic signal for the catalyst in the one-sensor bank. In essence, the invention assumes that a signal characteristic for the non-existent pre-catalyst EGO sensor in the one-sensor bank would be the same as the signal characteristic of the existing pre-catalyst EGO sensor in the two-sensor bank and calculates a diagnostic signal for the catalyst in the one-sensor bank accordingly. The diagnostic signal can be, for example, a ratio of the arc lengths between the post-catalyst and pre-catalyst EGO sensor signals.
Once the arc length ratios are calculated, the ratios can be compared with calibratable or experimentally-generated ratios to monitor the catalyst efficiency over time. As a result, the invention can monitor and diagnose the operation of the catalysts in both the one-sensor bank and the two-sensor bank even though the one-sensor bank does not have a matched pair of EGO sensors.
REFERENCES:
patent: 5074113 (1991-12-01), Matsuoka
patent: 5207057 (1993-05-01), Kayanuma
patent: 5228287 (1993-07-01), Kuronishi et al.
patent: 5233829 (1993-08-01), Komatsu
patent: 5247793 (1993-09-01), Yamada et al.
patent: 5255512 (1993-10-01), Hamburg et al.
patent: 5279114 (1994-01-01), Kurita et al.
patent: 5282360 (1994-02-01), Hamburg et al.
patent: 5351484 (1994-10-01), Wade
patent: 5359852 (1994-11-01), Curran et al.
patent: 5377484 (1995-01-01), Shimizu
patent: 5394691 (1995-03-01), Seki
patent: 5417058 (1995-05-01), Shimizu
patent: 5450837 (1995-09-01), Uchikawa
patent: 5485382 (1996-01-01), Seki et al.
patent: 5511377 (1996-04-01), Kotwicki
patent: 5570574 (1996-11-01), Yamashita et al.
patent: 5704339 (1998-01-01), Choe et al.
patent: 5706793 (1998-01-01), Orzel et al.
patent: 5749221 (1998-05-01), Kawahira et al.
patent: 5875628 (1999-03-01), Mitsutani
patent: 5894727 (1999-04-01), Zimlich
patent: 5899062 (1999-05-01), Jerger et al.
patent: 5948974 (1999-09-01), Mitsutani
patent: 6047542 (2000-04-01), Kinugasa et al.
patent: 6122910 (2000-09-01), Hoshi et al.
patent: 6301880 (2001-10-01), Cullen et al.
Behr Kenneth John
Booth Richard Andrew
Cullen Michael John
Sealy Brent Edward
Buckert John F.
Denion Thomas
Ford Global Technologies Inc.
Lippa Allan J.
Tran Binh
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