Fuel control compensation for secondary air system flow variation

• US 20060042232A1
• Filed: 08/13/2004
• Published: 03/02/2006
• Est. Priority Date: 08/13/2004
• Status: Active Grant

• Current Assignee: GM Global Technology Operations LLC (General Motors Company)
• Original Assignee: GM Global Technology Operations Incorporated (Motors Liquidation Co. GUC Trust)
• Inventors: Jess, Richard B., Smith, Stuart R., Eng, James A., Fulcher, Stephen K., Risse, Patrick L.
• Granted Patent: US 7,111,454 B2
• Time in Patent Office: Days
• US Class Current: 60/285
• CPC Class Codes: F02D 21/10 having secondary air added to the fuel-air mixture

Abstract

An engine control system and method maintains an optimum exhaust fuel to air ratio in an internal combustion engine. A secondary air injection (SAI) pressure is measured in an SAI system. The SAI pressure measurement is converted into an SAI flow value. A fuel compensation value is obtained based on the SAI flow value. Fuel delivery is compensated to the engine based on the fuel compensation value. In a second embodiment, the fuel compensation value is obtained based on the SAI pressure measurement. Fuel delivery is compensated to the engine based on the fuel compensation value. In a third embodiment, a primary flow value is calculated at an air intake of the engine. A fuel compensation value is calculated based on the SAI flow and primary flow values. Fuel delivery to the engine is compensated based on the fuel compensation value.

Claims

1. A control system for maintaining an optimum exhaust fuel to air ratio in an internal combustion engine, comprising:

an engine having an primary air intake and a fuel injection system;

an exhaust system connected to said engine and having a catalytic converter;

a secondary air injection (SAI) system connected to the exhaust system;

an SAI pressure sensor disposed in said SAI system that generates an SAI pressure measurement; and

a controller that communicates with said SAI pressure sensor, said primary intake and said fuel injection system and that compensates fuel delivery into said engine based on said SAI pressure measurement from said SAI pressure sensor.

2. The control system of claim 1 wherein said SAI pressure sensor is disposed in said secondary air injection (SAI) system upstream of said catalytic converter.

3. The control system of claim 1 wherein said SAI pressure sensor communicates an SAI pressure measurement to said controller.

4. The control system of claim 3 wherein said controller converts said SAI pressure measurement into an SAI flow value.

5. The control system of claim 3 wherein said controller determines fuel compensation based on said SAI pressure measurement and modifies fuel delivery of said fuel injection system based on said fuel compensation.

6. The control system of claim 4 wherein said controller determines fuel compensation based on said SAI flow value and modifies fuel delivery of said fuel injection system based on said fuel compensation.

7. The method of claim 4, further comprising a sensor that measures a primary flow value in said primary air intake.

8. The control system of claim 7 wherein said controller calculates a fuel compensation value based on said SAI flow value and said primary flow value.

9. The control system of claim 8 wherein said controller compensates fuel delivery to said engine based on said compensation value by one of reducing fuel delivery to said engine for a fuel compensation value below a predetermined value and increasing fuel delivery to said engine for a fuel compensation value above said predetermined value.

10. A method for maintaining an optimum exhaust fuel to air ratio in an internal combustion engine, comprising:

determining an optimum exhaust fuel to air ratio measuring a pressure in a secondary injection (SAI) system connected to an exhaust system of the engine;

converting said SAI pressure measurement into an SAI flow value;

obtaining a fuel compensation value based on said SAI flow value; and

compensating fuel delivery to said engine based on said fuel compensation value to achieve a predetermined target.

11. The method of claim 10 wherein measuring a pressure in a secondary air injection (SAI) system includes measuring a pressure in an SAI system that is connected to said exhaust system upstream of a catalytic converter.

12. The method of claim 10 wherein converting said SAI pressure measurement includes obtaining an SAI flow value from a function based on said SAI pressure measurement.

13. The method of claim 12 wherein obtaining a fuel compensation value includes determining a fuel compensation value from a function based on said SAI flow value.

14. The method of claim 10 wherein compensating includes one of reducing fuel delivery to said engine for a fuel compensation value below a predetermined value and increasing fuel delivery to said engine for a fuel compensation value above said predetermined value.

15. A method for maintaining an optimum exhaust fuel to air ratio in an internal combustion engine, comprising:

determining an optimum exhaust fuel to air ratio;

measuring a pressure in a secondary injection (SAI) system connected to an exhaust system of the engine;

generating a fuel compensation value based on said SAI pressure measurement; and

compensating fuel delivery to said engine based on said fuel compensation value to achieve a predetermined target.

16. The method of claim 15 wherein measuring a pressure includes measuring a pressure in a secondary injection (SAI) system connected to said exhaust system upstream of a catalytic converter.

17. The method of claim 15 wherein generating a fuel compensation value includes determining a fuel compensation value from a function based on said SAI pressure measurement.

18. The method of claim 15 wherein compensating fuel delivery includes one of reducing fuel delivery to said engine for an SAI pressure measurement below a predetermined value and increasing fuel delivery to said engine for an SAI pressure measurement above said predetermined value

19. A method for maintaining an optimum exhaust fuel to air ratio in an internal combustion engine having a fuel injection system and an exhaust system, comprising:

determining an optimum exhaust fuel to air ratio;

measuring a pressure in a secondary injection (SAI) system;

converting said SAI pressure measurement into an SAI flow value;

calculating a primary flow value at an air intake of said engine;

determining an uncompensated fuel to air ratio from said primary flow value and the fuel injection system;

obtaining a fuel compensation value based on said SAI flow value, said primary flow value and said uncompensated fuel to air ratio; and

compensating fuel delivery to said engine based on said fuel compensation value to achieve a predetermined target.

20. The method of claim 19 wherein measuring a pressure includes measuring a pressure in the secondary injection (SAI) system connected to the exhaust system upstream of a catalytic converter.

21. The method of claim 19 wherein converting said SAI pressure includes obtaining an SAI flow value from a function based on said SAI pressure measurement.

22. The method of claim 19 wherein calculating the primary flow value includes measuring a primary flow value with a sensor.

23. The method of claim 19 wherein obtaining a fuel compensation value is based on said SAI flow value, said primary flow value and said uncompensated fuel to air ratio.

24. The method of claim 19 wherein compensating includes one of reducing fuel delivery to said engine for a fuel compensation value below a predetermined value and increasing fuel delivery to said engine for a fuel compensation value above said predetermined value.