Air-Fuel ratio control system for internal combustion engine and control method thereof

• US 20020078683A1
• Filed: 12/26/2001
• Published: 06/27/2002
• Est. Priority Date: 12/26/2000
• Status: Active Grant

• Current Assignee: Toyota Jidosha Kabushiki Kaisha (Toyota Motor Corporation)
• Original Assignee: Toyota Jidosha Kabushiki Kaisha (Toyota Motor Corporation)
• Inventors: Katayama, Akihiro, Kato, Naoto, Kojima, Shinji, Baba, Naoki, Nagai, Toshinari, Kamoto, Akira
• Granted Patent: US 6,502,389 B2
• Time in Patent Office: Days
• US Class Current: 60/285
• CPC Class Codes: F01N 13/009 having two or more separate purifying devices arranged in series
• CPC Class Codes: F01N 13/011 having two or more purifying devices arranged in parallel
• CPC Class Codes: F02D 2200/0802 Temperature of the exhaust gas treatment apparatus
• CPC Class Codes: F02D 2200/0814 Oxygen storage amount
• CPC Class Codes: F02D 41/0295 Control according to the amount of oxygen that is stored on the exhaust gas treating apparatus
• CPC Class Codes: F02D 41/1441 Plural sensors
• CPC Class Codes: F02D 41/1456 with sensor output signal being linear or quasi-linear with the concentration of oxygen
• CPC Class Codes: F02D 41/1474 by detecting the commutation time of the sensor

Abstract

An air-fuel ratio control system for an internal combustion engine estimates an oxygen storage amount of a catalyst based on a record of an oxygen storage amount, and controls an air-fuel ratio based on the estimated oxygen storage amount. The catalyst is divided into multiple sections in a flow direction of an exhaust gas, the oxygen storage amount in a specified section is estimated according to a behavior of an exhaust gas on upstream and downstream sides of the respective specified sections, and the air-fuel ratio is controlled based on the estimated oxygen storage amount in the specified section.

Claims

1. An air-fuel ratio control system for an internal combustion engines comprising:

a controller that;

divides a catalyst provided in an exhaust passage of an internal combustion engine into multiple sections in a flow direction of an exhaust gas,

calculates a change in an oxygen storage amount in a specified section among the multiple sections based on an air-fuel ratio of an exhaust gas flowing into the catalyst,

estimates the oxygen storage amount in the specified section among the multiple sections based on a record of the change in the oxygen storage amount; and

controls the air-fuel ratio based on the estimated oxygen storage amount.

2. An air-fuel ratio control system according to claim 1, wherein:

the controller calculates an upstream side oxygen storage amount in an upstream section located upstream of the specified section based on the air fuel ratio of the exhaust gas flowing into the catalyst,

calculates an oxygen amount flowing into respective sections located downstream of the upstream section sequentially based on the upstream side oxygen storage amount,

estimates the oxygen storage amount in the specified section based on the oxygen amount flowing into respective sections located between the upstream section and the specified section.

3. The air-fuel ratio control system according to claim 1, wherein:

the controller changes a position of the specified section in accordance with an operation status of the internal combustion engine.

4. The air-fuel ratio control system according to claim 3, wherein:

the controller changes the position of the specified section to a farther upstream position as an air intake volume increases.

5. The air-fuel ratio control system according to claim 3, wherein:

the controller changes the position of the specified section to a farther upstream position as a bed temperature of the catalyst decreases.

6. The air-fuel ratio control system according to claim 3, wherein:

the controller changes the position of the specified section to a farther upstream position as a deviation of an exhaust air-fuel ratio of an exhaust gas flowing into the catalyst with respect to a stoichiometric air fuel ratio increases.

7. The air-fuel ratio control system according to claim 3, wherein:

the controller changes the position of the specified section to a farther upstream position as a deterioration degree of the catalyst increases.

8. The air-fuel ratio control system according to claim 1, wherein:

the controller changes a unit length of the respective specified sections in accordance with an operation status of the internal combustion engine.

9. The air-fuel ratio control system according to claim 8, wherein:

the controller decreases the unit length of the respective specified sections as an air intake volume is increased.

10. The air-fuel ratio control system according to claim 8, wherein:

the controller decreases the unit length of the respective specified sections as a bed temperature of the catalyst is decreased.

11. The air-fuel ratio control system according to claim 8, wherein:

the controller decreases the unit length of the respective specified sections as a deviation of an exhaust air-fuel ratio of an exhaust gas flowing into the catalyst with respect to a stoichiometric air fuel ratio is increased.

12. The air-fuel ratio control system according to claim 8, wherein:

the controller decreases the unit length of the respective specified sections as a deterioration degree of the catalyst is increased.

13. The air-fuel ratio control system according to claim 1, wherein:

a plurality of the specified sections are designated, and the controller controls the air-fuel ratio such that the oxygen storage amounts in the plurality of the specified sections satisfy respective targeted values.

14. The air-fuel ratio control system according to claim 13, wherein:

the controller controls the air-fuel ratio such that the oxygen storage amounts in the plurality of the specified sections satisfy a targeted value sequentially from a downstream side to an upstream side.

15. The air-fuel ratio control system according to claim 13, wherein:

the controller controls the air-fuel ratio such that the oxygen storage amounts in the plurality of the specified sections satisfy a targeted value sequentially from an upstream side to a downstream side.

17. The air-fuel ratio control system according to claim 16, wherein:

the controller calculates the change in the oxygen storage amount in an upstream side of an upstream section located upstream of the specified section based on the air fuel ratio of the exhaust gas flowing into the catalyst, and

estimates the oxygen storage amount in the specified section based on an oxygen amount flowing into the respective sections located downstream of the upstream section, the oxygen amount being calculated based on the change in oxygen storage amount in the upstream side.

18. The air-fuel ratio control system according to claim 16, wherein:

the controller changes a position of the specified section in accordance with an operation status of the internal combustion engine.

19. The air-fuel ratio control system according to claim 16, wherein:

the controller changes a unit length of the respective sections in accordance with the operation status of the internal combustion engine.

20. The air-fuel ratio control system according to claim 16, wherein:

a plurality of the specified sections are designated, and the controller controls the air-fuel ratio such that the oxygen storage amounts in the plurality of the specified sections satisfy respective targeted values.

16. The air-fuel ratio control system for an internal combustion engines comprising:

a controller that;

divides a catalyst provided in an exhaust passage of an internal combustion engine into multiple sections in a flow direction of an exhaust gas,

calculates a change in an oxygen storage amount in a specified section among the multiple sections based on an air-fuel ratio of an exhaust gas flowing into the catalyst,

estimates the oxygen storage amount in the specified section based on a record of the change in the oxygen storage amount; and

controls the air-fuel ratio based on the oxygen storage amount in the specified section.

21. An air-fuel ratio control method for an internal combustion engine comprising the steps of:

dividing a catalyst provided in an exhaust passage of the internal combustion engine into multiple sections in a flow direction of the exhaust gas,

calculating a change in an oxygen storage amount in a specified section among the multiple sections based on an air-fuel ratio of an exhaust gas flowing into the catalyst,

estimating the oxygen storage amount in the specified section based on a record of the change in the oxygen storage amount, and

controlling the air-fuel ratio based on the estimated oxygen storage amount.

22. The air-fuel ratio control method according to claim 21, wherein

the oxygen storage amount in an upstream section located upstream of the specified section is calculated based on the air fuel ratio of the exhaust gas flowing into the catalyst in the calculating step, and

the oxygen storage amount in the specified section is estimated based on an oxygen amount flowing into the respective sections located downstream of the upstream section, the oxygen amount being calculated based on the oxygen storage amount in the estimating step.

23. The air-fuel ratio control method according to claim 21, wherein:

the position of the specified section is changed in accordance with an operation status of the internal combustion engine in the calculating step.

24. The air-fuel ratio control method according to claim 21, wherein:

the unit length of the respective sections is changed in accordance with an operation status of the internal combustion engine in the calculating step.

25. The air fuel ratio control method according to claim 21, wherein:

a plurality of the specified sections are designated, and the air-fuel ratio is controlled such that the oxygen storage amounts in the respective specified sections satisfy respective targeted values.