Granted Patent B2

US 8,464,518 · App. 10/739,616 · Granted Jun 18, 2013

Abstract

Claims (49)

1. An engine system including an engine, an exhaust system, and a fuel system that communicates with the engine, comprising:

a controller that communicates with the fuel system and that controls a first quantity of liquid fuel to the engine at a first air/fuel (A/F) ratio and a second quantity of vapor fuel to the engine at a second A/F ratio to provide a fuel mixture having a third A/F ratio; and

a secondary air source that operates in at least one of an on state and an off state and when operating in said on state supplies air to the exhaust system to increase said third A/F ratio,

wherein said controller receives an indication of said at least one of said on state and said off state and adjusts said first quantity of liquid fuel and said second quantity of vapor fuel based on said indication, and

wherein said controller further receives an exhaust A/F ratio from an exhaust A/F ratio sensor, compares said exhaust A/F ratio to a target A/F ratio range, and adjusts said first and second quantities when said exhaust A/F ratio is outside of said target A/F ratio range.

2. The engine system of claim 1 wherein said first A/F ratio is lower than a stoichiometric A/F ratio.

3. The engine system of claim 1 wherein said controller controls an initial A/F ratio of liquid fuel supplied to the engine and estimates said third A/F ratio based thereon.

4. The engine system of claim 1 wherein said controller calculates an NF ratio offset based on said exhaust A/F ratio and a target A/F ratio.

5. The engine system of claim 1 wherein said controller determines an available A/F ratio of vapor fuel within the fuel system, performs a comparison with a target A/F ratio range, and wherein said second quantity is set to zero if said A/F ratio of said vapor fuel is outside of said target A/F ratio range.

6. The engine system of claim 5 wherein said controller adjusts said available A/F ratio based on an A/F ratio offset.

7. A method of operating a combustion engine with a secondary air source, comprising:

supplying liquid fuel having a first A/F ratio to the engine;

receiving an indication of an operational state of the secondary air source;

supplying liquid fuel at a second A/F ratio and vapor fuel at a third A/F ratio to the engine based on said indication to produce an exhaust A/F ratio;

receiving a second exhaust A/F ratio from an exhaust A/F ratio sensor

comparing said second exhaust A/F ratio to a target A/F ratio; and

adjusting flow of said liquid fuel and said vapor fuel when said second exhaust A/F ratio is not equal to said target A/F ratio.

8. The method of claim 7 wherein said second A/F ratio is less than a stoichiometric A/F ratio.

9. The method of claim 7 further comprising calculating said third A/F ratio based on said first A/F ratio.

10. The method of claim 7 further comprising controlling a valve in communication with a supply of vapor fuel to regulate said vapor fuel.

11. The method of claim 7 further comprising:

determining an A/F ratio offset based on said second exhaust A/F ratio and said target A/F ratio;

storing said A/F ratio offset; and

adjusting said third A/F ratio based on said A/F ratio offset.

12. The method of claim 7 further comprising:

determining an available A/F ratio of vapor fuel within a fuel tank; and

comparing said available A/F ratio with a target A/F ratio range, wherein said third A/F ratio is zero if said available A/F ratio is outside of said target A/F ratio range.

13. The method of claim 12 further comprising adjusting said available A/F ratio based on an A/F ratio offset.

14. A method of operating a combustion engine with a secondary air source comprising:

receiving an indication of an operational state of the secondary air source;

determining a first A/F ratio of a first supply of liquid fuel;

determining a second A/F ratio of a second supply of vapor fuel based on said first A/F ratio and said indication;

supplying said first supply of liquid fuel and said second supply of vapor fuel to the engine;

supplying air to exhaust gas from the engine while the secondary air source is operational;

comparing an exhaust A/F ratio to a target A/F ratio; and

adjusting said first supply and second supply when said exhaust A/F ratio is not equal to said target A/F ratio.

15. The method of claim 14 wherein said first A/F ratio is less than a stoichiometric A/F ratio.

16. The method of claim 14 further comprising controlling a valve in communication with a supply of vapor fuel to regulate said second supply of vapor fuel.

17. The method of claim 14 further comprising:

determining a third A/F ratio of a third supply of liquid fuel supplied to said engine during starting; and

calculating said second A/F ratio based on said third A/F ratio.

18. The method of claim 17 further comprising:

determining an A/F ratio offset based on said exhaust A/F ratio and said target A/F ratio;

storing said A/F ratio offset; and

adjusting said third A/F ratio based on said A/F ratio offset.

19. The method of claim 14 further comprising:

determining an available A/F ratio of vapor fuel within a fuel tank; and

comparing said available A/F ratio with a target A/F ratio range, wherein said second supply is zero if said available A/F ratio is outside of said target A/F ratio range.

20. The method of claim 19 further comprising adjusting said available A/F ratio based on an A/F ratio offset.

Assignments (13)