METHOD AND SYSTEM FOR FUEL VAPOR CONTROL

• US 20110168140A1
• Filed: 05/28/2010
• Published: 07/14/2011
• Est. Priority Date: 05/28/2010
• Status: Active Grant

• Current Assignee: Ford Global Technologies, LLC (Ford Motor Company)
• Original Assignee: Ford Global Technologies, LLC (Ford Motor Company)
• Inventors: Sullivan, Patrick, Ferguson, Russ William, Euliss, William, Pearce, Russell Randall, DeBastos, Timothy, Dudar, Aed, Kluzner, Michael Igor, Bohr, Scott, Kerns, James Michael, Jentz, Robert Roy, Gabor, Daniel, Kragh, Christopher
• Granted Patent: US 8,056,540 B2
• Time in Patent Office: Days
• US Class Current: 123/521
• CPC Class Codes: F02M 25/0818 having means for pressurising the evaporative emission space

Abstract

A method and system for fuel vapor control in a hybrid vehicle (HEV). The HEV fuel vapor recovery system includes a fuel tank isolation valve, which is normally closed to isolate storage of refueling from storage of diurnal vapors. The method for fuel vapor control includes selectively actuating the fuel tank isolation valve during interrelated routines for refueling, fuel vapor purging, and emission system leak detection diagnostics to improve regulation of pressure and vacuum the HEV fuel vapor recovery system.

Claims

1. A method of monitoring a fuel vapor recovery system including a canister, and a vacuum accumulator including a venturi, comprising,

during a first engine-on condition, flowing air or exhaust through the venturi to generate and store vacuum in the vacuum accumulator;

and

during a subsequent engine-off condition, applying vacuum from the vacuum accumulator on the canister, and indicating degradation based on a change in fuel vapor recovery system pressure following vacuum application.

2. The method of claim 1, wherein the fuel vapor recovery system further includes a fuel tank, further comprising, applying vacuum on the fuel tank during the engine-off condition.

3. The method of claim 1, wherein flowing air or exhaust through the venturi includes, flowing ambient air, engine exhaust, or a brake pump exhaust through the venturi to generate the vacuum.

4. The method of claim 3, wherein applying vacuum from the vacuum accumulator includes opening a vacuum accumulator valve coupling the vacuum accumulator to the canister, opening a fuel tank isolation valve coupling the fuel tank to the canister, and closing a canister purge valve coupling the canister to an engine intake.

5. The method of claim 4, wherein indicating degradation includes indicating fuel tank isolation valve degradation in response to, following vacuum application, a change in canister pressure over time being greater than a threshold, and indicating purge valve degradation in response to a change in canister pressure over time being greater than a threshold.

6. The method of claim 1, wherein vacuum application is delayed based on an amount of vacuum in the vacuum accumulator.

7. The method of claim 6, wherein the delay includes continuing engine operation until the amount of vacuum in the vacuum accumulator exceeds a threshold, and discontinuing engine operation when the amount of vacuum exceeds the threshold.

8. The method of claim 2, further comprising, during a purging condition, purging a first amount of fuel vapors from the canister to the engine intake, and after purging the first amount, purging a second amount of fuel vapors from the fuel tank to the canister, the second amount of fuel vapors adjusted based on the first amount.

9. The method of claim 2, further comprising,

during a first engine-off condition, when a fuel tank absolute pressure is greater than a threshold, applying vacuum or pressure on the fuel tank before applying vacuum or pressure on the canister;

and

during a second engine-off condition, when a fuel tank absolute pressure is lower than the threshold, applying vacuum on the canister before applying vacuum on the fuel tank.

10. The method of claim 9, wherein indicating degradation includes, during the first or second engine-off condition, indicating degradation based on a change in fuel tank pressure over time or a change in canister pressure, upon vacuum application.

11. A method of monitoring a vehicle fuel vapor recovery system including a fuel tank, a canister, and a vacuum accumulator, the vacuum accumulator including a venturi, the method comprising,

during a first engine-on condition, flowing exhaust through the venturi to generate a vacuum, and storing the vacuum in the vacuum accumulator;

and

during a subsequent engine-off condition, applying a vacuum from the vacuum accumulator on the fuel tank or the canister, and indicating fuel vapor recovery system degradation based on a change in fuel vapor recovery system pressure following the vacuum application.

12. The method of claim 11, wherein the venturi is coupled to a brake pump, and wherein flowing exhaust through the venturi includes flowing brake pump exhaust through the venturi during brake pump operation.

13. The method of claim 12, wherein the vacuum application is delayed and an engine operation is continued at least until a vacuum in the vacuum accumulator is above a threshold.

14. The method of claim 11, wherein applying the vacuum from the vacuum accumulator includes opening a vacuum accumulator valve coupling the vacuum accumulator to the canister, and opening a fuel tank isolation valve coupling the fuel tank to the canister.

15. The method of claim 14, wherein indicating degradation includes indicating fuel tank isolation valve degradation in response to, following vacuum application, a change in a fuel tank pressure over time being greater than a threshold or a change in a canister pressure over time being greater than a threshold, and indicating canister purge valve degradation in response to a change in the canister pressure over time being greater than a threshold.

16. The method of claim 15, wherein the fuel tank pressure is estimated by a first pressure sensor coupled to the fuel tank, and the canister pressure is estimated by a second pressure sensor coupled to the canister.

17. A vehicle system, comprising,

a battery;

an engine that is selectively started in response to a battery state of charge falling below a threshold;

a brake system including brakes and a brake booster pump;

a fuel tank coupled to a canister through a fuel tank isolation valve;

a canister, configured to store fuel vapors, coupled to an engine intake through a canister purge valve;

a vacuum accumulator coupled to the canister through a vacuum accumulator valve, the vacuum accumulator including a venturi;

a first pressure sensor coupled to the fuel tank to estimate a fuel tank pressure;

a second pressure sensor coupled to the canister to estimate a canister pressure; and

a control system with computer readable instructions for,

during an engine-on mode of vehicle operation, flowing exhaust through the venturi to generate a vacuum, the vacuum stored in the vacuum accumulator; and

during a subsequent engine-off mode of vehicle operation, applying vacuum from the vacuum accumulator on the canister and/or the fuel tank, and indicating fuel vapor recovery system degradation based on a change in fuel vapor recovery system pressure following vacuum application.

18. The system of claim 17, wherein the engine-on mode of vehicle operation is continued until a vacuum in the vacuum accumulator exceeds a threshold and wherein flowing exhaust through the venturi includes, flowing brake booster pump exhaust through the venturi during brake application.

20. The system of claim 17, wherein flowing exhaust through the venturi includes, flowing ambient air through the venturi during vehicle motion and wherein applying the vacuum from the vacuum accumulator includes opening the vacuum accumulator valve and the fuel tank isolation valve, and wherein indicating degradation includes setting a diagnostic code.

23. The system of claim 17, wherein indicating degradation includes indicating fuel tank isolation valve degradation in response to, following vacuum application, a change in fuel tank pressure over time being greater than a threshold or a rate of change of canister pressure over time being greater than a threshold, and indicating canister purge valve degradation in response to a change in canister pressure over time being greater than a threshold.

19. (canceled)

21. (canceled)

22. (canceled)