US5313791A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Method for detecting catalyst malfunctions
Assignee: Ford Global Technologies LLC
•
Filing: 1993-04-07
•
Granted: 1994-05-24
•
Expires: 2013-04-07
Abstract
Abstract A method of detecting catalyst malfunction in a vehicle uses an exhaust gas oxygen sensor downstream of the catalyst. A feedback loop controls the air-fuel ratio as a function of the output signal from the exhaust gas oxygen sensor. The feedback gain is increased from low gain to high gain and then operational parameters are examined. In a first version the amplitude of the exhaust gas oxygen sensor is used as an indication. In a second version, the amplitude of the exhaust gas oxygen sensor reaches a predetermined limit and then the feedback gain is examined. In a third version, limit-cycle operation is reached and the frequency of the limit-cycle is examined with respect to a predetermined frequency.
Inventors
- 👤 Douglas R. Hamburg
- 👤 Jeffrey A. Cook
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-05 10:55
CPC Classifications
F; F01; F01N; F01N11/00; F01N11/007; F01N2550/00; F01N2550/02; Y; Y02; Y02T; Y02T10/00; Y02T10/10; Y02T10/40
Claims Analysis
Total Claims: 19
Claim 1
Independent Claim
90 words
A method of detecting catalyst malfunction in a vehicle using an exhaust gas oxygen sensor downstream of the catalyst including the steps of: providing a feedback loop to control air-fuel ratio as a function of the signal from the exhaust gas oxygen sensor; increasing feedback loop gain by altering operating parameters of the feedback loop until a desired characteristic of an output of the exhaust gas oxygen sensor is achieved; and establishing catalyst malfunction as a function of the output of the exhaust gas oxygen sensor and the feedback gain.
Claim 2
Independent Claim
90 words
A method of detecting catalyst malfunction in a vehicle using an exhaust gas oxygen sensor downstream of the catalyst including the steps of: providing a feedback loop to control air-fuel ratio as a function of the signal from the exhaust gas oxygen sensor; increasing feedback loop gain by altering operating parameters of the feedback loop until a desired characteristic of an output of the exhaust gas oxygen sensor is achieved; and establishing catalyst malfunction as a function of the output of the exhaust gas oxygen sensor and the feedback gain.
Claim 3
Dependent Claim
66 words
A method as recited in claim 1, wherein the step of increasing the feedback gain is done until a predetermined fluctuation amplitude of an output of the exhaust gas oxygen sensor is reached and the step of establishing catalyst malfunction includes determining the feedback gain, comparing it to a predetermined feedback gain, and indicating malfunction when the feedback gain is greater than the predetermined feedback gain.
Claim 4
Dependent Claim
46 words
A method as recited in claim 2, wherein there is an automatic adjustment of the feedback gain of the feedback loop to maintain the exhaust gas oxygen sensor output fluctuations at the predetermined amplitude so that as the catalyst conversion efficiency decreases, the gain automatically increases.
Claim 5
Dependent Claim
110 words
A method as recited in claim 1, including the steps of: initially setting the gain of the post-catalyst feedback loop at a sufficiently low value at the beginning of the catalyst testing interval to avoid a high amplitude limit-cycle oscillation which would saturate the exhaust gas oxygen sensor downstream of the catalyst; increasing the gain until a clearly defined limit-cycle oscillation is developed as indicated by the output of the exhaust gas oxygen sensor downstream of the catalyst; holding the gain constant during the remainder of the testing interval; determining the frequency of the limit-cycle; and establishing catalyst failure when the limit-cycle frequency is greater than a certain predetermined value.
Claim 6
Independent Claim
94 words
A method of detecting catalyst malfunction in a vehicle using an exhaust gas oxygen sensor downstream of the catalyst including the steps of: applying a low gain to a feedback loop from the exhaust gas oxygen sensor downstream of the catalyst; examining the amplitude fluctuations of the exhaust gas oxygen sensor output; determining there is a high catalyst conversion efficiency if there are high amplitude fluctuations; determining there is a low catalyst conversion efficiency if there are low amplitude fluctuations; and establishing a catalyst failure when the amplitude fluctuations are below a predetermined amount.
Claim 7
Independent Claim
94 words
A method of detecting catalyst malfunction in a vehicle using an exhaust gas oxygen sensor downstream of the catalyst including the steps of: applying a low gain to a feedback loop from the exhaust gas oxygen sensor downstream of the catalyst; examining the amplitude fluctuations of the exhaust gas oxygen sensor output; determining there is a high catalyst conversion efficiency if there are high amplitude fluctuations; determining there is a low catalyst conversion efficiency if there are low amplitude fluctuations; and establishing a catalyst failure when the amplitude fluctuations are below a predetermined amount.
Claim 8
Independent Claim
113 words
A method of detecting catalyst malfunction in a vehicle using an exhaust gas oxygen sensor downstream of the catalyst including the steps of: applying a low gain to a post-catalyst feedback loop; increasing the gain in the feedback loop until the amplitude fluctuations of the post-catalyst EGO sensor output reach a predetermined value; determining there is high conversion efficiency if a low gain is required to produce the predetermined value; determining there is a low conversion efficiency if a high gain is required to produce the predetermined value; determining the amount of gain required to produce the predetermined value; and establishing a catalyst failure when the gain is greater than a predetermined amount.
Claim 9
Independent Claim
113 words
A method of detecting catalyst malfunction in a vehicle using an exhaust gas oxygen sensor downstream of the catalyst including the steps of: applying a low gain to a post-catalyst feedback loop; increasing the gain in the feedback loop until the amplitude fluctuations of the post-catalyst EGO sensor output reach a predetermined value; determining there is high conversion efficiency if a low gain is required to produce the predetermined value; determining there is a low conversion efficiency if a high gain is required to produce the predetermined value; determining the amount of gain required to produce the predetermined value; and establishing a catalyst failure when the gain is greater than a predetermined amount.
Claim 10
Independent Claim
90 words
A method of detecting catalyst malfunction in a vehicle using exhaust gas oxygen sensor downstream of a catalyst including the steps of: applying a low gain to a post-catalyst feedback loop for controlling air-fuel ratio; increasing the gain in the feedback loop until the amplitude fluctuations of the post-catalyst EGO sensor output reach an air-fuel ratio limit-cycle operation; holding the gain constant at this level; measuring the limit-cycle frequency while the gain is held constant; and establishing a catalyst failure when the limit-cycle frequency is greater than a predetermined frequency.
Claim 11
Independent Claim
90 words
A method of detecting catalyst malfunction in a vehicle using exhaust gas oxygen sensor downstream of a catalyst including the steps of: applying a low gain to a post-catalyst feedback loop for controlling air-fuel ratio; increasing the gain in the feedback loop until the amplitude fluctuations of the post-catalyst EGO sensor output reach an air-fuel ratio limit-cycle operation; holding the gain constant at this level; measuring the limit-cycle frequency while the gain is held constant; and establishing a catalyst failure when the limit-cycle frequency is greater than a predetermined frequency.
Claim 12
Independent Claim
166 words
An apparatus for detecting catalyst malfunction in a vehicle using an exhaust gas oxygen sensor downstream of the catalyst including: a feedback loop to control air-fuel ratio as a function of the signal from the exhaust gas oxygen sensor; means for increasing the feedback gain until a desired fluctuation amplitude of the exhaust gas oxygen sensor is achieved; means for initially setting the gain of the post-catalyst feedback loop at a low value at the beginning of the catalyst testing interval to avoid a high amplitude limit-cycle oscillation which would saturate the exhaust gas oxygen sensor downstream of the catalyst, means for increasing the gain until a clearly defined limit-cycle oscillation is developed as indicated by the output of the exhaust gas oxygen sensor downstream of the catalyst; means for holding the gain constant during the remainder of the testing interval; means for determining the frequency of the limit-cycle; and means for establishing catalyst failure when the limit-cycle frequency is greater than a certain predetermined value.
Claim 13
Independent Claim
166 words
An apparatus for detecting catalyst malfunction in a vehicle using an exhaust gas oxygen sensor downstream of the catalyst including: a feedback loop to control air-fuel ratio as a function of the signal from the exhaust gas oxygen sensor; means for increasing the feedback gain until a desired fluctuation amplitude of the exhaust gas oxygen sensor is achieved; means for initially setting the gain of the post-catalyst feedback loop at a low value at the beginning of the catalyst testing interval to avoid a high amplitude limit-cycle oscillation which would saturate the exhaust gas oxygen sensor downstream of the catalyst, means for increasing the gain until a clearly defined limit-cycle oscillation is developed as indicated by the output of the exhaust gas oxygen sensor downstream of the catalyst; means for holding the gain constant during the remainder of the testing interval; means for determining the frequency of the limit-cycle; and means for establishing catalyst failure when the limit-cycle frequency is greater than a certain predetermined value.
Claim 14
Independent Claim
101 words
An apparatus for detecting catalyst malfunction in a vehicle using an exhaust gas oxygen sensor downstream of the catalyst including: means for applying a low gain to a feedback loop from the exhaust gas oxygen sensor downstream of the catalyst; means for examining the amplitude fluctuations of the exhaust gas oxygen sensor output; means for determining there is a high catalyst conversion efficiency if there are high amplitude fluctuations; means for determining there is a low catalyst conversion efficiency if there are low amplitude fluctuations; and means for establishing a catalyst failure when the amplitude fluctuations are below a predetermined amount.
Claim 15
Independent Claim
101 words
An apparatus for detecting catalyst malfunction in a vehicle using an exhaust gas oxygen sensor downstream of the catalyst including: means for applying a low gain to a feedback loop from the exhaust gas oxygen sensor downstream of the catalyst; means for examining the amplitude fluctuations of the exhaust gas oxygen sensor output; means for determining there is a high catalyst conversion efficiency if there are high amplitude fluctuations; means for determining there is a low catalyst conversion efficiency if there are low amplitude fluctuations; and means for establishing a catalyst failure when the amplitude fluctuations are below a predetermined amount.
Claim 16
Independent Claim
122 words
An apparatus for detecting catalyst malfunction in a vehicle using an exhaust gas oxygen sensor downstream of the catalyst including: means for applying a low gain to a post-catalyst feedback loop; means for increasing the gain in the feedback loop until the amplitude fluctuations of the post-catalyst EGO sensor output reach a predetermined value; means for determining there is high conversion efficiency if a low gain is required to produce the predetermined value; means for determining there is a low conversion efficiency if a high gain is required to produce the predetermined value; means for determining the amount of gain required to produce the predetermined value; and means for establishing a catalyst failure when the gain is greater than a predetermined amount.
Claim 17
Independent Claim
122 words
An apparatus for detecting catalyst malfunction in a vehicle using an exhaust gas oxygen sensor downstream of the catalyst including: means for applying a low gain to a post-catalyst feedback loop; means for increasing the gain in the feedback loop until the amplitude fluctuations of the post-catalyst EGO sensor output reach a predetermined value; means for determining there is high conversion efficiency if a low gain is required to produce the predetermined value; means for determining there is a low conversion efficiency if a high gain is required to produce the predetermined value; means for determining the amount of gain required to produce the predetermined value; and means for establishing a catalyst failure when the gain is greater than a predetermined amount.
Claim 18
Independent Claim
93 words
An apparatus for detecting catalyst malfunction in a vehicle using exhaust gas oxygen sensor downstream of the catalyst including: means for applying a low gain to a post-catalyst feedback loop; means for increasing the gain in the feedback loop until the amplitude fluctuations of the post-catalyst EGO sensor output reach an air-fuel ratio limit-cycle operation; means for holding the gain constant at this level; means for measuring the limit-cycle frequency while the gain is held constant; and means for establishing a catalyst failure when the limit-cycle frequency is greater than a predetermined frequency.
Claim 19
Independent Claim
93 words
An apparatus for detecting catalyst malfunction in a vehicle using exhaust gas oxygen sensor downstream of the catalyst including: means for applying a low gain to a post-catalyst feedback loop; means for increasing the gain in the feedback loop until the amplitude fluctuations of the post-catalyst EGO sensor output reach an air-fuel ratio limit-cycle operation; means for holding the gain constant at this level; means for measuring the limit-cycle frequency while the gain is held constant; and means for establishing a catalyst failure when the limit-cycle frequency is greater than a predetermined frequency.
References Cited (Backward Citations)
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1997-05-23 | 1997-11-22 | 1998-05-24 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 2001-05-23 | 2001-11-22 | 2002-05-24 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 2005-05-23 | 2005-11-22 | 2006-05-24 | $7700.00 | Window Closed / Lapsed |