Patent US4729220A successfully refreshed from Google Patents.
US4729220A
Expired / Lapsed
US
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Air/fuel ratio control system for lean combustion engine using three-way catalyst
Assignee: Nissan Motor Co Ltd
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Filing: 1987-03-12
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Granted: 1988-03-08
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Expires: 2007-03-12
Abstract
Abstract The invention relates to a control system for feedback control of the air/fuel ratio in an internal combustion engine which uses a three-way catalyst to purify the exhaust gas, and which may be an automotive engine, by using an exhaust sensor to detect actual values of air/fuel ratio in the engine. The control system has the function of varying the target value of air/fuel ratio according to operating conditions of the engine such that the target value becomes super-stoichiometric at least in a portion of a steady zone of the engine operating conditions. The control system includes means to detect the temperature of the three-way catalyst and means to vary the feed of fuel or air to the engine when the catalyst temperature is above a predetermined level, e.g. 750° C., while the target value of the air/fuel ratio is super-stoichiometric such that the actual air/fuel ratio decreases to a predetermined value, e.g. stoichiometric value, which is optimum for the activities of the three-way catalyst, or to a still lower value. Such intentional change in the air/fuel ratio under the high exhaust temperature condition is effective in preventing early deterioration of the three-way catalyst.
Inventors
- 👤 Katsunori Terasaka
- 👤 Makoto Saitoh
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-24 19:07
CPC Classifications
F; F02; F02D; F02D41/00; F02D41/02; F02D41/14; F02D41/1438; F02D41/1473; F02D41/1475; F02D41/021; F02D41/0235; F02D41/1477; F02D41/1479; F02D2200/00; F02D2200/02; F02D2200/08; F02D2200/0802; Y; Y02; Y02T; Y02T10/00; Y02T10/10; Y02T10/12
Claims Analysis
Total Claims: 7
Claim 1
Independent Claim
221 words
A control system for feedback control of the air/fuel ratio of an air-fuel mixture supplied to an internal combution engine which uses a three-way catalyst for purifying the exhaust gas, the control system comprising: air/fuel ratio detection means for detecting actual values of air/fuel ratio in the engine; load detection means for detecting the load under which the engine is operating; temperature detection means for detecting the temperature of the three-way catalyst; and control means for performing feedback control of the feed of fuel or air to the engine based on the detected actual values of air/fuel ratio, the control means comprising target value setting means for determining a variable target value of the air/fuel ratio according to information obtained by said load detection means such that the target value becomes higher than the stoichiometric air/fuel ratio at least in a portion of a steady zone of operating conditions of the engine and modification means for varying the feed of fuel or air to the engine when the temperature of the three-way catalyst is above a predetermined temperature while the target value of feedback control of air/fuel ratio is higher than the stoichiometric ratio such that the actual air/fuel ratio decreases to a predetermined value which is optimum for the activities of the three-way catalyst or to a still lower value.
Claim 2
Dependent Claim
221 words
A control system for feedback control of the air/fuel ratio of an air-fuel mixture supplied to an internal combution engine which uses a three-way catalyst for purifying the exhaust gas, the control system comprising: air/fuel ratio detection means for detecting actual values of air/fuel ratio in the engine; load detection means for detecting the load under which the engine is operating; temperature detection means for detecting the temperature of the three-way catalyst; and control means for performing feedback control of the feed of fuel or air to the engine based on the detected actual values of air/fuel ratio, the control means comprising target value setting means for determining a variable target value of the air/fuel ratio according to information obtained by said load detection means such that the target value becomes higher than the stoichiometric air/fuel ratio at least in a portion of a steady zone of operating conditions of the engine and modification means for varying the feed of fuel or air to the engine when the temperature of the three-way catalyst is above a predetermined temperature while the target value of feedback control of air/fuel ratio is higher than the stoichiometric ratio such that the actual air/fuel ratio decreases to a predetermined value which is optimum for the activities of the three-way catalyst or to a still lower value.
Claim 3
Dependent Claim
15 words
A control system according to claim 1, wherein said predetermined temperature is about 750° C.
Claim 4
Dependent Claim
23 words
A control system according to claim 1, wherein said predetermined value of the air/fuel ratio is approximately equal to the stoichiometric air/fuel ratio.
Claim 5
Dependent Claim
38 words
A control system according to claim 1, wherein at least said control means, a part of said air/fuel ratio detection means, a part of said load detection means and said temperature detection means are integrated in a microcomputer.
Claim 6
Dependent Claim
46 words
A control system according to claim 4, wherein said temperature detection means comprises a group of data which is stored in said microcomputer and indicates an experimentally determined temperature of the three-way catalyst for each of a plurality of zones of operating conditions of the engine.
Claim 7
Dependent Claim
25 words
A control system according to claim 1, wherein said air/fuel ratio detection means comprises means for sensing the concentration of oxygen in the exhaust gas.
References Cited (Backward Citations)
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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) | 1991-03-08 | 1991-09-07 | 1992-03-08 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1995-03-08 | 1995-09-07 | 1996-03-08 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1999-03-08 | 1999-09-07 | 2000-03-08 | $7700.00 | Window Closed / Lapsed |