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US4561399A
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Method of controlling air-fuel ratio
Assignee: Toyota Motor Corp
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Filing: 1984-08-24
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Granted: 1985-12-31
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Expires: 2004-08-24
Abstract
Abstract There is disclosed a control of learning correction coefficient compensating an aging of the air flow meter and a high altitude of highlands where the motor vehicle travels. A lower limit for a altitude compensating learning correction coefficient FHAC is computed by use of the altitude compensating learning correction coefficient FHAC determined during idling of the engine. A feedback correction coefficient FAF is determined such that it gets greater as the air-fuel ratio becomes smaller than the stoichiometric level of air-fuel ratio and it gets smaller as the air-fuel ratio becomes greater than the stoichiometric level of air-fuel ratio. When the mean value FAFAV1 of the feedback correction coefficient FAF is equal to the predetermined value or more, the altitude compensating learning correction coefficient FHAC is increased. Whereas, the mean value FAFAV1 is less than the predetermined value, the altitude compensating learning correction coefficient FHAC is decreased. The altitude compensating learning correction coefficient FHAC is not exceeded the lower limit therefor.
Inventors
- 👤 Nobuyuki Kobayashi
- 👤 Takashi Hattori
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-02 17:25
CPC Classifications
F; F02; F02D; F02D41/00; F02D41/02; F02D41/14; F02D41/1497; F02D41/04; F02D41/047; F02D41/18; F02D41/24; F02D41/2406; F02D41/2425; F02D41/2429; F02D41/2451; F02D41/2454; F02D41/30; F02D41/32; F02D41/08; F02D41/2441; F02D41/2474
Claims Analysis
Total Claims: 14
Claim 1
Independent Claim
171 words
A method of controlling an air-fuel ratio comprising the steps of: determining a basic fuel injection time duration on the basis of an engine load and an engine speed; determining a feedback correction coefficient in accordance with a measured air-fuel ratio so that the air-fuel ratio becomes a stoichiometric air-fuel ratio under a predetermined feedback condition; increasing an altitude compensating learning correction coefficient when a mean value of the feedback correction coefficient reaches a predetermined value or more, and, decreasing the altitude compensating learning correction coefficient when the mean value is less than the predetermined value; determining a lower limit on the basis of the altitude compensating learning correction coefficient determined during idling of a motor vehicle so as not to bring the altitude compensating learning correction coefficient into a value less than the lower limit; and determining a final fuel injection time duration in accordance with the basic fuel injection time duration and the altitude compensating learning correction coefficient, whereby fuel is injected for the final fuel injection time duration.
Claim 2
Independent Claim
171 words
A method of controlling an air-fuel ratio comprising the steps of: determining a basic fuel injection time duration on the basis of an engine load and an engine speed; determining a feedback correction coefficient in accordance with a measured air-fuel ratio so that the air-fuel ratio becomes a stoichiometric air-fuel ratio under a predetermined feedback condition; increasing an altitude compensating learning correction coefficient when a mean value of the feedback correction coefficient reaches a predetermined value or more, and, decreasing the altitude compensating learning correction coefficient when the mean value is less than the predetermined value; determining a lower limit on the basis of the altitude compensating learning correction coefficient determined during idling of a motor vehicle so as not to bring the altitude compensating learning correction coefficient into a value less than the lower limit; and determining a final fuel injection time duration in accordance with the basic fuel injection time duration and the altitude compensating learning correction coefficient, whereby fuel is injected for the final fuel injection time duration.
Claim 3
Dependent Claim
63 words
A method of controlling an air-fuel ratio as set forth in claim 1 further comprising the steps: determining, when the throttle valve is fully closed, a guard value on the basis of the altitude compensating learning correction coefficient such that it approach the altitude compensating learning correction coefficient, wherein the lower limit is determined by subtracting a predetermined value from the guard value.
Claim 4
Dependent Claim
68 words
A method of controlling an air-fuel ratio as set in claim 1, wherein, when the measured air-fuel ratio is on the rich side, the feedback correction coefficient is computed in a manner to approach a value less than 1.0 and, when the measured air-fuel ratio is on the lean side, the feedback correction coefficient FAF is computed in a manner to approach a value being 1.0 or more.
Claim 5
Dependent Claim
163 words
A method of controlling an air-fuel ratio as set forth in claim 1, wherein: the air-fuel ratio is detected by an oxygen sensor for outputing an air-fuel ratio signal in acoordance with a concentration of oxygen in the exhaust gas, said air-fuel ratio signal being low level when the concentration of oxygen is high and being high level when the concentration of oxygen is low; when the air-fuel ratio signal becomes lower than a predetermined reference value, a comparatively high value is added to the feedback correction coefficient to be skipped, and until the air-fuel ratio reaches the predetermined reference value or more, a comparatively low value is added to the feedback correction coefficient; and when the air-fuel ratio reaches the predetermined reference value or more, a comparatively high value is subtracted from the feedback correction coefficient to be skipped, and until the air-fuel ratio becomes lower than the predetermined reference value, a comparatively low value is subtracted from the feedback correction coefficient.
Claim 6
Dependent Claim
43 words
A method of controlling an air-fuel ratio as set forth in claim 4, wherein the mean value of the feedback correction coefficient is computed by an airthmetical mean of the feedback correction coefficients immediately before two successive skips of the feedback correction coefficient.
Claim 7
Dependent Claim
55 words
A method of controlling an air-fuel ratio as set forth in claim 5, wherein when the mean value is 1 and more, a predetermined number is added to the altitude compensating learning correction coefficient, and when the mean value is less than 1, the predetermined number is subtracted from the altitude compensating learning correction coefficient.
Claim 8
Independent Claim
205 words
A method of controlling an air-fuel ratio comprising the steps of: determining a basic fuel injection time duration on the basis of an intake air flowrate and an engine rotational speed; determining a feedback correction coefficient in accordance with a measured air-fuel ratio so that the air-fuel ratio becomes a stoichiometric air-fuel ratio under a predetermined feedback condition; determining, when a throttle valve is fully closed, a reference value such that it approaches a mean value of the feedback correction coefficient; judging as to whether the reference value is within a predetermined range when the throttle valve is fully closed increasing an obstruction compensating learning correction coefficient when the judging is made that the reference value is within the predetermined range and the mean value of the feedback correction coefficient reaches a predetermined value, and decreasing the obstruction compensating learning correction coefficient when the judging is made that the reference value is within the predetermined range and the mean value of the feedback correction coefficient less than the predetermined value; and determining a final fuel injection time duration in accordance with the basic fuel injection time duration and the obstruction compensating learning correction coefficient, whereby fuel is injection for the final fuel injection time duration.
Claim 9
Independent Claim
205 words
A method of controlling an air-fuel ratio comprising the steps of: determining a basic fuel injection time duration on the basis of an intake air flowrate and an engine rotational speed; determining a feedback correction coefficient in accordance with a measured air-fuel ratio so that the air-fuel ratio becomes a stoichiometric air-fuel ratio under a predetermined feedback condition; determining, when a throttle valve is fully closed, a reference value such that it approaches a mean value of the feedback correction coefficient; judging as to whether the reference value is within a predetermined range when the throttle valve is fully closed increasing an obstruction compensating learning correction coefficient when the judging is made that the reference value is within the predetermined range and the mean value of the feedback correction coefficient reaches a predetermined value, and decreasing the obstruction compensating learning correction coefficient when the judging is made that the reference value is within the predetermined range and the mean value of the feedback correction coefficient less than the predetermined value; and determining a final fuel injection time duration in accordance with the basic fuel injection time duration and the obstruction compensating learning correction coefficient, whereby fuel is injection for the final fuel injection time duration.
Claim 10
Dependent Claim
67 words
A method of controlling an air-fuel ratio as set in claim 7, wherein, when the measured air-fuel ratio is on the rich side, the feedback correction coefficient is computed in a manner to approach a value less than 1.0 and, when the measured air-fuel ratio is on the lean side, the feedback correction coefficient is computed in a manner to approach a value being 1.0 or more.
Claim 11
Dependent Claim
59 words
A method of controlling an air-fuel ratio as set forth in claim 8, wherein the reference value is set at 1.0 at the time of the start of an engine, and, only when the reference value is 0.98 or more or 1.02 or less, the predetermined number is added to or subtracted from the obstruction compensating learning correction coefficient.
Claim 12
Dependent Claim
38 words
A method of controlling an air-fuel ratio as set forth claim 7, wherein, after the predetermined number is added to or subtracted from the obstruction compensating learning correction coefficient, a predetermined value is added to the reference value.
Claim 13
Dependent Claim
162 words
A method of controlling an air-fuel ratio as set forth in claim 7, wherein: the air-fuel ratio is detected by an oxygen sensor for outputing an air-fuel ratio signal in accordance with a concentration of oxygen in the exhaust gas, said air-fuel ratio signal being low level when the concentration of oxygen is high and being high level when the concentration of oxygen is low; when the air-fuel ratio signal becomes lower than a predetermined reference value, a comparatively high value is added to the feedback correction coefficient to be skipped, and until the air-fuel ratio reaches the predetermined reference value or more, a comparatively low value is added to the feedback correction coefficient; when the air-fuel ratio reaches the predetermined reference value or more, a comparatively high value is subtracted from the feedback correction coefficient to be skipped, and until the air-fuel ratio becomes lower than the predetermined reference value, a comparatively low value is subtracted from the feedback correction coefficient.
Claim 14
Dependent Claim
43 words
A method of controlling an air-fuel ratio as set forth in claim 11, wherein the mean value of the feedback correction coefficient is computed by an arithmetical mean of the feedback correction coefficients immediately before two successive skips of the feedback correction coefficient.
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) | 1988-12-30 | 1989-07-01 | 1989-12-31 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1992-12-30 | 1993-07-01 | 1993-12-31 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1996-12-30 | 1997-07-01 | 1997-12-31 | $7700.00 | Window Closed / Lapsed |