Compensation for fuel volatility for internal combustion engine start and run

• US 20030213475A1
• Filed: 05/16/2002
• Published: 11/20/2003
• Est. Priority Date: 05/16/2002
• Status: Active Grant

• Current Assignee: Delphi Technologies Ip Limited (BorgWarner Incorporated)
• Original Assignee: Delphi Technologies, Inc. (Aptiv PLC)
• Inventors: Burleigh, Darrell W., Carlson, Craig A., Garcia, Sergio Eduardo, Robertson, William R.
• Granted Patent: US 6,679,225 B2
• Time in Patent Office: Days
• US Class Current: 123/491
• CPC Class Codes: F02D 19/0623 Failure diagnosis or prevention; Safety measures; Testing
• CPC Class Codes: F02D 19/0631 by estimation, i.e. without using direct measurements of a corresponding sensor
• CPC Class Codes: F02D 19/0636 by estimation, i.e. without using direct measurements of a corresponding sensor
• CPC Class Codes: F02D 19/0649 Liquid fuels having different boiling temperatures, volatilities, densities, viscosities, cetane or octane numbers
• CPC Class Codes: F02D 2200/0611 Fuel type, fuel composition or fuel quality
• CPC Class Codes: F02D 2200/1015 Engines misfires
• CPC Class Codes: F02D 35/027 using knock sensors
• CPC Class Codes: F02D 41/0025 Controlling engines characterised by use of non-liquid fuels, pluralities of fuels, or non-fuel substances added to the combustible mixtures
• CPC Class Codes: F02D 41/062 for starting F02D41/061 takes precedence
• CPC Class Codes: F02D 41/1497 With detection of the mechanical response of the engine
• CPC Class Codes: F02D 41/1498 measuring engine roughness
• CPC Class Codes: Y02T 10/30 Use of alternative fuels, e.g. biofuels

Abstract

The present invention provides an improvement over conventional engine controls by adjusting engine air/fuel [AF] ratio, as a function of fuel volatility, during engine start and initial operation. It is comprised of three detection tests to determine the volatility of the fuel and provide compensation to the AF ratio in proportion to that volatility during engine crank and initial operation. The method includes compensating for incomplete fuel vaporization as a function of predicted intake valve temperature.

Claims

1. A method for fueling an internal combustion engine during crank, comprising:

sensing one or more predetermined engine parameters;

determining a base crank AF ratio as a function of the sensed one or more predetermined engine parameters;

determining a mass of air delivered to the engine as a function of the sensed one or more predetermined engine parameters;

selecting a stored crank AF adjustment term;

calculating a crank AF ratio by combining the base crank AF ratio with said crank AF adjustment term; and

determining fueling by combining the crank AF ratio with the mass of air delivered.

2. The method in claim 1, wherein the step of selecting the stored crank AF adjustment term comprises the steps of:

measuring engine crank time;

comparing the engine crank time to a threshold engine crank time that is a function of the one or more predetermined engine parameters;

selecting a crank AF compensation term as a function of a difference between the measured engine crank time and the threshold engine crank time, when said engine crank time exceeds said threshold engine crank time; and

setting a crank AF adjustment term equal to the crank AF compensation term, when the crank AF compensation term is greater than the crank AF adjustment term.

3. The method in claim 2, wherein the method to determine the crank AF adjustment term includes reducing the crank AF adjustment term by a decay value when the crank AF adjustment term is greater than the crank AF compensation term.

4. The method in claim 3, wherein the method to determine the crank AF adjustment term includes storing the crank AF adjustment term in memory for use in subsequent engine starting events.

5. The method in claim 1, wherein the method to determine the crank AF adjustment term includes setting the crank AF adjustment term to a preset value prior to initial engine start.

6. The method in claim 5, wherein the method to determine the crank AF adjustment term includes setting the crank AF adjustment term to the preset value when it has been detected that a fuel supply has been replenished.

7. The method in claim 5, wherein the method to determine the crank AF adjustment term includes setting the crank AF adjustment term to the preset value when it has been detected that engine misfire has occurred.

8. A method for fueling an internal combustion engine during initial engine operation after start, comprising:

sensing predetermined engine parameters;

determining a base run AF ratio as a function of the sensed engine parameters;

determining a mass of air delivered to the engine as a function of the sensed engine parameters;

determining a run AF adjustment term as a function of fuel volatility;

calculating a run AF ratio by combining the base run AF ratio with the run AF adjustment term; and

determining fueling by combining the run AF ratio with the mass of air delivered.

9. The method in claim 8, wherein the method for determining the run AF adjustment term during initial engine operation comprises:

determining a first AF compensation term as a function of engine sag after start;

determining a second AF compensation term as a function of engine roughness;

selecting a greater value from a comparison of the first AF compensation term and second AF compensation term as a resultant;

comparing the resultant with a run AF adjustment term; and

determining the run AF adjustment term to be equal to the resultant when the resultant is greater than the run AF adjustment term.

10. The method in claim 9, wherein the method for determining the run AF adjustment term includes reducing the run AF adjustment term by a decay value when the resultant is less than the run AF adjustment term.

11. The method in claim 10, wherein the method for determining the run AF adjustment term includes storing the run AF adjustment term in memory for use in subsequent engine operation events.

12. The method in claim 9, wherein determining the first AF compensation term comprises:

measuring engine speed until a specific time after engine start has been determined;

comparing the engine speed to a desired engine speed; and

selecting the first AF compensation term from a table as a function of the ratio of the engine speed and the predetermined engine speed, when the engine speed is less than said desired engine speed.

13. The method in claim 9, wherein determining the second AF compensation term comprises:

measuring engine roughness during initial engine operation;

comparing the engine roughness to a roughness threshold; and

selecting the second AF compensation term from a table as a function of the engine roughness when the engine roughness exceeds the roughness threshold.

14. The method in claim 8, wherein the method to determine the run AF adjustment term includes setting the run AF adjustment term to a preset value prior to initial engine run.

15. The method in claim 9, wherein the method to determine the first AF compensation term includes setting the first AF compensation term to a preset value prior to initial engine run.

16. The method in claim 9, wherein the method to determine the second AF compensation term includes setting the second AF compensation term to a preset value prior to initial engine run.

17. The method in claim 14, wherein the method to determine the run AF adjustment term includes setting the run AF adjustment term to the preset value when it has been detected that the fuel supply has been replenished.

18. The method in claim 14, wherein the method to determine the run AF adjustment term includes setting the run AF adjustment term to the preset value when it has been detected that engine misfire has occurred.

19. The method in claim 15, wherein the method to determine the first AF compensation term includes setting the first AF compensation term to the preset value when it has been detected that the fuel supply has been replenished.

20. The method in claim 15, wherein the method to determine the first AF compensation term includes setting the first AF compensation term to the preset value when it has been detected that engine misfire has occurred.

21. The method in claim 16, wherein the method to determine the second AF compensation term includes setting the second AF compensation term to the preset value when it has been detected that the fuel supply has been replenished.

22. The method in claim 16, wherein the method to determine the second AF compensation term includes setting the second AF compensation term to the preset value when it has been detected that engine misfire has occurred.

23. The method in claim 12, wherein the specific time after engine start is five seconds.

24. The method in claim 9, wherein determining the second AF compensation term comprises:

measuring engine roughness during initial engine operation;

determining an intake valve temperature;

comparing the measured engine roughness to a roughness threshold until the intake valve temperature exceeds a threshold value; and

selecting the second AF compensation term from a table as a function of the engine roughness when the engine roughness exceeds the roughness threshold.

25. A method for determining a run AF ratio in an internal combustion engine during initial engine operation, comprising

determining a run AF adjustment term based upon fuel volatility;

and

combining a base run AF ratio with the run AF compensation term.

26. The method in claim 25, wherein determining the run AF adjustment term comprises:

determining a first AF compensation term based upon engine flare performance;

determining a second AF compensation term based upon engine roughness; and

selecting a greater value from a comparison of the first AF compensation term and the second AF compensation term.