US5423203A
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US
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Failure determination method for O2 sensor
Assignee: Mitsubishi Motors Corp
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Filing: 1993-07-16
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Granted: 1995-06-13
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Expires: 2013-07-16
Abstract
Abstract A failure determination method for an O 2 sensor is provided wherein the air-fuel ratio of a mixture is maintained at a value which produces a leaner or richer air-fuel ratio than a stoichiometric ratio by a predetermined value, for a predetermined time after an engine starts operating in an idle region, to thereby make the oxygen concentration of exhaust gas surrounding the O 2 sensor uniform. Subsequently, the air-fuel ratio is forcibly subjected to an oscillatory change with a predetermined amplitude of ±10 to 15% of the stoichiometric ratio with respect to the stoichiometric ratio at a predetermined frequency of several Hz, to determine abnormality of the O 2 sensor based on the change of the output voltage of the O 2 sensor.
Inventors
- 👤 Koichi Namiki
- 👤 Takuya Matsumoto
- 👤 Toru Hashimoto
- 👤 Yasuhisa Yoshida
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-06 06:15
CPC Classifications
F; F02; F02D; F02D41/00; F02D41/02; F02D41/14; F02D41/1438; F02D41/1493; F02D41/1495; F02D41/22; F02D41/222; F01; F01N; F01N2550/00; F01N2560/00; F01N2560/02; F01N2560/025
Claims Analysis
Total Claims: 13
Claim 1
Independent Claim
152 words
A failure determination method for an O 2 sensor which detects oxygen concentration of an exhaust gas from an internal combustion engine, comprising the steps of: (a) maintaining an air-fuel ratio of a mixture supplied to the internal combustion engine at a rich or lean value, with respect to a stoichiometric air-fuel ratio, for a first predetermined time period; (b) forcibly subjecting the air-fuel ratio to an oscillatory change such that the air-fuel ratio alternately varies between a rich value with respect to the stoichiometric air-fuel ratio and a lean value with respect to the stoichiometric air-fuel ratio after a lapse of said first predetermined time period; (c) detecting change of an output voltage of the O 2 sensor during the forcibly subjected oscillatory change of the air-fuel ratio; and (d) determining abnormality of the O 2 sensor based on the detected change of the output voltage of the O 2 sensor.
Claim 2
Dependent Claim
152 words
A failure determination method for an O 2 sensor which detects oxygen concentration of an exhaust gas from an internal combustion engine, comprising the steps of: (a) maintaining an air-fuel ratio of a mixture supplied to the internal combustion engine at a rich or lean value, with respect to a stoichiometric air-fuel ratio, for a first predetermined time period; (b) forcibly subjecting the air-fuel ratio to an oscillatory change such that the air-fuel ratio alternately varies between a rich value with respect to the stoichiometric air-fuel ratio and a lean value with respect to the stoichiometric air-fuel ratio after a lapse of said first predetermined time period; (c) detecting change of an output voltage of the O 2 sensor during the forcibly subjected oscillatory change of the air-fuel ratio; and (d) determining abnormality of the O 2 sensor based on the detected change of the output voltage of the O 2 sensor.
Claim 3
Dependent Claim
49 words
A failure determination method according to claim 1, wherein said step (a) of maintaining the air-fuel ratio is started upon detecting operation of the internal combustion engine in a predetermined operating condition in which an amount of intake air for the internal combustion engine is below a predetermined value.
Claim 4
Dependent Claim
95 words
A failure determination method according to claim 1, wherein said step (d) of determining abnormality of the O 2 sensor comprises the substeps of: (1) detecting a time period elapsed from a start of the oscillatory change of the air-fuel ratio until the output voltage of the O 2 sensor reaches a predetermined voltage value, as a parameter representing the change of the output voltage of the O 2 sensor; and (2) judging that operation of the O 2 sensor is abnormal when the detected elapsed time period is longer than a predetermined time period.
Claim 5
Dependent Claim
39 words
A failure determination method according to claim 1, wherein the forcibly subjected oscillatory change of the air-fuel ratio in step (b) is carried over a time period which is shorter than the first predetermined time period of step (a).
Claim 6
Dependent Claim
33 words
A failure determination method according to claim 1, wherein an air-fuel ratio set in step (a) is different from the rich air-fuel ratio and the lean air-fuel ratio varied between in step (b).
Claim 7
Dependent Claim
54 words
A failure determination method according to claim 4, wherein said step (b) of forcibly subjecting the air-fuel ratio to an oscillatory change is started upon detecting operation of the internal combustion engine in a predetermined operating condition in which an amount of intake air for the internal combustion engine is below a predetermined value.
Claim 8
Dependent Claim
18 words
A failure determination method according to claim 6, wherein said predetermined operating condition comprises an idle operating condition.
Claim 9
Dependent Claim
43 words
The failure determine method of claim 4, wherein said step (b) of forcibly subjecting oscillatory change to the air-fuel ratio includes subjecting the air-fuel ratio to an oscillatory change with a predetermined amplitude at a predetermined frequency over a second predetermined time period.
Claim 10
Dependent Claim
32 words
A failure determination method according to claim 8, wherein said predetermined amplitude is ±10 to 15% with respect to the stoichiometric air-fuel ratio, and said predetermined frequency is smaller than 10 Hz.
Claim 11
Dependent Claim
134 words
A failure determination method according to claim 4, wherein said step (d) of determining abnormality of the O 2 sensor comprises the substeps of: (1) detecting an amplitude value of the output voltage of the O 2 sensor in at least one cycle of oscillation of the air-fuel ratio during a time period from a start of the oscillatory change to a time when a plurality of cycles of oscillation of the air-fuel ratio are completed, as a parameter representing the change of the output voltage of the O 2 sensor; and (2) determining abnormality of the 0 2 sensor based on a result of a comparison between the detected amplitude value of the output voltage of the 0 2 sensor in said at least one cycle of oscillation and a predetermined voltage value.
Claim 12
Dependent Claim
78 words
A failure determination method according to claim 10, wherein abnormality of the O 2 sensor is determined in step (d) by detecting the amplitude value of the output voltage of the O 2 sensor In each of said plurality of cycles of oscillation, calculating a mean value of the detected amplitude values as a parameter representing the change of the output voltage of the O 2 sensor, and comparing the calculated mean value with the predetermined voltage value.
Claim 13
Dependent Claim
37 words
A failure determination method according to claim 4, which further comprises a step (e) of notifying abnormality of the O 2 sensor to a driver when abnormality of the O 2 sensor is determined in step (d).
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USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1998-06-12 | 1998-12-12 | 1999-06-13 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 2002-06-12 | 2002-12-12 | 2003-06-13 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 2006-06-12 | 2006-12-12 | 2007-06-13 | $7700.00 | Window Closed / Lapsed |