Claims
- 1. An air-fuel ratio controller for an internal combustion engine comprising:
- an oxygen density sensor provided in an exhaust system of said engine for detecting an oxygen density in an exhaust gas of said engine and generating an output signal indicative thereof;
- memory means for storing a plurality of predetermined non-linear relationships between a) an air-fuel ratio deviation, and b) said oxygen density sensor output signal, over an entire range;
- air fuel-ratio deviation determining means for determining a current air-fuel ratio deviation by using said output of said oxygen density sensor and one of said plural predetermined non-linear relationships stored in said memory means;
- control variable setting means for setting an air-fuel ratio control variable according to said deviation determined by said air-fuel ratio deviation determining means;
- air-fuel ratio control means for controlling an air-fuel ratio of mixed gas to be supplied to said engine toward said desired air-fuel ratio according to said control variable set by said control variable setting means;
- characteristic change detection means for detecting a change in an output characteristic of said oxygen density sensor for a predetermined air-fuel ratio by using said output of said oxygen density sensor; and
- selection means for correcting said one of said plural predetermined non-linear relationships over said entire range corresponding to a detection result of said characteristic change detection means.
- 2. An air-fuel ratio controller according to claim 1, wherein said memory means stores a plurality of relationships between said air-fuel ratio deviation and said oxygen density sensor output and wherein said correction means selects one of said plural relationships stored in said memory means as a selected relationship corresponding to said detection result of said characteristic change detection means.
- 3. An air-fuel ratio controller according to claim 2, wherein each of said plural relationships are determined corresponding to a difference in a magnitude or said output of said oxygen density sensor generated in a specific operating state.
- 4. An air-fuel ratio controller according to claim 3, wherein said plural relationships are stored in said memory means as two-dimensional maps.
- 5. An air-fuel ratio controller according to claim 1, wherein said characteristic change detecting means detects a characteristic change of said oxygen density sensor according to a magnitude of said oxygen density sensor output generated in a specific operating state of said internal combustion engine.
- 6. An air-fuel ratio controller according to claim 5 wherein said specific operating state is a state where air-fuel ratio of mixed gas to be supplied is enriched.
- 7. An air-fuel ratio controller according to claim 1, wherein said selection means corrects a magnitude of said air-fuel ratio deviation determined by said air-fuel ratio deviation determining means to a larger value for the same output of said oxygen density sensor when a deterioration of said oxygen density sensor is detected by said characteristic change detection means than when one is not detected.
- 8. An air-fuel ratio controller according to claim 1 further comprising:
- air-fuel ratio enriching means for enriching said air-fuel ratio of said mixed gas to be supplied to said engine more than said desired air-fuel ratio regardless of said signal coming from said oxygen density sensor when said engine operates in a specific state, and
- said characteristic change detection means detecting said change in said output characteristic of said oxygen density sensor in a state where said air-fuel ratio of said mixed gas is enriched more than said desired air-fuel ratio by said air-fuel ratio enriching means.
- 9. An air-fuel ratio controller for an internal combustion engine comprising:
- an oxygen density sensor provided in an exhaust system of said engine for detecting an oxygen density in an exhaust gas of said engine and generating an output signal indicative thereof;
- memory means for storing at least one predetermined relationship between an air-fuel ratio deviation and an oxygen density sensor output over an entire range of operation;
- air-fuel ratio deviation determining means for determining a current air-fuel ratio deviation corresponding to said output signal of said oxygen density sensor on the basis of said relationship stored in said memory means;
- control variable setting means for setting an air-fuel ratio control variable according to said deviation determined by said air-fuel ratio deviation determining means;
- air-fuel ratio control means for controlling an air-fuel ratio of mixed gas to be supplied to said engine toward said desired air-fuel ratio in response to said control variable set by said control variable setting means;
- operating state detection means for detecting an operating sate of said engine;
- decision means for determining that a condition wherein said operating state detected by said operating state detecting means reaches a predetermined operating state;
- characteristic change detection means for detecting a change in an output characteristic of said oxygen density sensor for a predetermined air-fuel ratio when said condition is determined by said decision means; and
- correction means for correcting said relationship stored in said memory means over said entire range corresponding to a detection result of said characteristic change detection means.
- 10. An air-fuel ratio controller according to claim 9, wherein said characteristic change detection means detects said change in said output characteristic of said oxygen density sensor when the realized condition determined by said decision means lasts for more than a predetermined time.
- 11. An air-fuel ratio controller according to claim 9, wherein plural relationships between said air fuel ratio deviation and said oxygen density sensor output are stored in said memory means, and said correction means selects one of said plural relationships stored in said memory means as a selected relationship corresponding to said detection result of said characteristic change detection means.
- 12. An air-fuel ratio controller according to claim 11, wherein said plural relationships are stored in said memory as a plurality of maps each determined corresponding to a difference in a magnitude of said oxygen density sensor output generated in a specific operating state.
- 13. An air-fuel ratio controller according to claim 12, wherein each of said plural relationships are stored in said memory means as a two-dimensional map for computing said air-fuel ratio deviation based on said oxygen density sensor output generated in said specific operating state and in an occasional operating state as parameters.
- 14. An air-fuel ratio control system for an engine comprising:
- air-fuel ratio detecting means for detecting an air-fuel ratio of a mixture supplied to said engine;
- memory means for storing therein a predetermined relationship between an air-fuel ratio of mixture and an output of said air-fuel ratio detecting means over an entire range;
- deviation detecting means for detecting, from said predetermined relationship, a deviation of said detected air-fuel ratio from a desired air-fuel ratio;
- correction value setting means for setting a correction value in response to said detected deviation, said correction value being variable in proportion to said detected deviation;
- integrating means for integrating said correction value set by said setting means;
- mixture control means for controlling, in accordance with an output of said integrating means, an air-fuel ratio of mixture to be supplied to said engine;
- deterioration detecting means for detecting a deterioration of said air-fuel ratio detecting means; and
- correction means for correcting said predetermined relationship over said entire range in response to said detected deterioration.
- 15. An air-fuel ratio control system as set forth in claim 14, wherein said deterioration detecting means comprises:
- enrichment detecting means for detecting enrichment of air-fuel ratio of mixture to be supplied to said engine; and
- discriminating means for discriminating, in response to the detected enrichment, whether said air-fuel ratio detecting means is deteriorated in accordance with a magnitude of said output of said air-fuel ratio detecting means.
- 16. An air-fuel ratio control system as set forth in claim 14, wherein said memory means stores a plurality of relationships between said air-fuel ratio of mixture and said output of said air-fuel ratio detecting means and said relationships vary from each other in dependence on the degree of deterioration of said air-fuel ratio detecting means, and wherein one of said relationships is selected in response to an output of said deterioration detecting means.
- 17. An air-fuel ratio control system as set forth in claim 16, wherein said deterioration detecting means is responsive to a magnitude of said output of said air-fuel ratio detecting means at the time of enrichment of said air-fuel mixture to be supplied to said engine.
- 18. An air-fuel ratio apparatus for an internal combustion engine comprising:
- an oxygen density sensor, located in a path of an exhaust gas of said engine, for determining an oxygen density in the exhaust gas of said engine and generating an oxygen density sensor output signal indicative thereof;
- memory means for storing a plurality of predetermined non-linear relationships between an air-fuel ratio and said oxygen density sensor output signal, each relationship being over an entire range of operation of said oxygen density sensor output;
- characteristic change detection means for detecting a change in an output characteristic of said oxygen density sensor for a predetermined air-fuel ratio using said output of said oxygen density sensor;
- selection means for correcting at least one of said plural predetermined non-linear relationships to produce corrected non-linear relationships over said entire range corresponding to a detection result of said characteristic change detection means;
- means for determining a current air-fuel ratio deviation by using said output of said oxygen density sensor and one of said corrected non-linear relationships stored in said memory means; and
- air-fuel ratio control means for controlling an air-fuel ration of mixed gas to be supplied to said engine toward a desired air-fuel ratio based on said current air-fuel ratio obtained based on said corrected non-linear relationships.
- 19. An apparatus as in claim 18, wherein said air fuel ratios stored by said memory means are air fuel ratio deviations, and further comprising:
- air fuel-ratio deviation determining means for determining a current air-fuel ratio deviation by using said output of said oxygen density sensor and said selected relationship.
- 20. An apparatus as in claim 19, further comprising:
- control variable setting means for setting an air-fuel ratio control variable according to said deviation determined by said air-fuel ratio deviation determining means; and
- wherein said air-fuel ratio control means controls an air-fuel ratio of mixed gas to be supplied to said engine toward said desired air-fuel ratio according to said control variable set by said control variable setting means.
- 21. A method of controlling an air-fuel ratio in an internal combustion engine comprising the steps of:
- detecting an oxygen density in an exhaust gas of said engine and generating an output signal indicative thereof;
- storing a plurality of predetermined relationships between an air-fuel ratio and said oxygen density output signal, each said relationship being over an entire range of operation;
- detecting a change in an output characteristic of said oxygen density output signal for a predetermined air-fuel ratio;
- correcting at least one of said plural predetermined non-linear relationships to produce corrected non-linear relationships over said entire range;
- determining a current air-fuel ratio deviation by using said oxygen density output signal and one of said corrected non-linear relationships; and
- controlling an air-fuel ratio of mixed gas to be supplied to said engine toward a desired air-fuel ratio based on said corrected non-linear relationships.
- 22. A method as in claim 21, wherein said air fuel ratio parameter is an air fuel ratio deviation, and comprising the further steps of:
- setting an air-fuel ratio control variable according to said determined deviation; and
- wherein said controlling step includes controlling an air-fuel ratio of mixed gas to be supplied to said engine toward said desired air-fuel ratio according to said control variable.
Priority Claims (1)
Number |
Date |
Country |
Kind |
63-229186 |
Sep 1988 |
JPX |
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Parent Case Info
This is a continuation of application Ser. No 07/406,725, filed on Sep. 12, 1989, which was abandoned upon the filing hereof.
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Continuations (1)
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Number |
Date |
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Parent |
406725 |
Sep 1989 |
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