METHOD AND SYSTEM FOR FUEL VAPOR CONTROL

• US 20110295482A1
• Filed: 05/28/2010
• Published: 12/01/2011
• 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: Olson, Chad Michael, Bohr, Scott, Kerns, James Michael, Sullivan, Patrick, Pearce, Russell Randall, Kragh, Christopher, DeBastos, Timothy
• Granted Patent: US 8,447,495 B2
• Time in Patent Office: Days
• US Class Current: 701/102
• CPC Class Codes: B60K 15/03504 adapted to avoid loss of fuel or fuel vapour, e.g. with vapour recovery systems
• CPC Class Codes: B60K 15/03519 Valve arrangements in the vent line
• CPC Class Codes: B60K 2015/0319 with electronic systems, e.g. for controlling fuelling or venting for LPG tanks B60K2015/03013
• CPC Class Codes: B60K 2015/03302 Electromagnetic valves
• CPC Class Codes: B60K 6/48 Parallel type
• CPC Class Codes: B60W 20/00 Control systems specially adapted for hybrid vehicles hybrid vehicle design, B60K6/00; electric vehicles B60L
• CPC Class Codes: F02D 29/02 peculiar to engines driving vehicles; peculiar to engines driving variable pitch propellers
• CPC Class Codes: F02D 41/0032 Controlling the purging of the canister as a function of the engine operating conditions
• CPC Class Codes: F02M 25/0818 having means for pressurising the evaporative emission space
• CPC Class Codes: F02M 33/00 Other apparatus for treating combustion-air, fuel or fuel-air mixture combustion-air cleaners F02M35/00; arrangements for purifying liquid fuel F02M37/22
• CPC Class Codes: Y02T 10/62 Hybrid vehicles

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 operating a fuel vapor recovery system including a fuel tank and a canister coupled to an engine intake, 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 adjusted based on the first amount.

2. The method of claim 1, wherein the purging condition includes a canister pressure being greater than a first threshold.

3. The method of claim 2, wherein the fuel tank is coupled to the canister through a first valve, and the canister is coupled to the engine intake through a second valve, and wherein purging the first amount includes maintaining the first valve closed to isolate the fuel tank from the canister while opening the second valve to couple the canister to the engine intake.

4. The method of claim 3, wherein purging the second amount includes opening the first valve to couple the fuel tank to the canister.

5. The method of claim 4, wherein during purging of the second amount, opening of the first valve is adjusted based on at least one of a canister pressure and a fuel tank pressure.

6. The method of claim 5, wherein the adjustment of the first valve includes opening the first valve when at least one of the canister pressure is lower than the first threshold and the fuel tank pressure is greater than a second threshold.

7. The method of claim 6, wherein the fuel tank pressure is estimated by a first pressure sensor coupled to the fuel tank, and wherein the canister pressure is estimated by a second pressure sensor coupled to the canister.

8. The method of claim 7, further comprising, after purging the second amount, closing the first valve.

9. The method of claim 1, further comprising, in response to a request for refueling, delaying purging of the first amount and the second amount at least until refueling is completed.

10. The method of claim 8, wherein completion of refueling is indicated by at least one of a fuel tank pressure exceeding a threshold, a refueling door sensor indicating a refueling door being closed, and a fuel level sensor exceeding a threshold, and wherein purging of the first or second amount is initiated in response to the completion of refueling.

11. A vehicle system, comprising,

a battery;

an engine including an engine intake, the engine selectively started and stopped responsive to a battery state of charge;

a fuel system comprising,

a fuel tank with a first opening for receiving fuel and a second opening for delivering fuel vapors along a first conduit;

a canister with a first opening for receiving air from an atmosphere, a second opening for receiving fuel vapors from the fuel tank along the first conduit, and a third opening for relaying stored fuel vapors to an engine intake along a second conduit;

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

a fuel tank isolation valve, positioned in the first conduit, coupling the fuel tank to the canister;

a canister purge valve, positioned in the second conduit, coupling the canister to the engine intake;

a canister vent valve coupled to the first opening of the canister,

a first pressure sensor in the first conduit for estimating a fuel tank pressure;

a second pressure sensor in the second conduit for estimating a canister pressure; and

a control system with computer readable instructions for,

during a purging condition, when the canister pressure is greater than a threshold,

isolating the fuel tank while purging a first amount of fuel vapors from the canister to the engine intake;

after purging the first amount of fuel vapors, coupling the fuel tank and purging a second amount of fuel vapors from the fuel tank, the second amount adjusted based on the first amount; and

after purging the second amount, isolating the fuel tank.

12. The system of claim 11, wherein isolating the fuel tank includes closing the fuel tank isolation valve and coupling the fuel tank includes opening the fuel tank isolation valve.

13. The system of claim 12, wherein purging the first amount includes opening the canister purging valve and the canister vent valve.

14. The system of claim 13, wherein purging the second amount includes closing the canister purge valve and the canister vent valve to purge fuel vapors to the canister when the fuel tank pressure is below a threshold, and opening the canister purging valve and the canister vent valve to purge fuel vapors to the engine intake when the fuel tank pressure is above a threshold.

15. The system of claim 11, wherein the control system further includes instructions for, in response to a request for refueling, delaying purging until refueling is completed.

16. The system of claim 15, wherein refueling includes, opening a fuel tank door and receiving fuel in the fuel tank after the fuel tank pressure has dropped below a threshold.

17. The system of claim 16, wherein a completion of refueling is indicated by at least one of the fuel tank pressure exceeding the threshold, a fuel door sensor indicating a refueling door is closed, and a fuel level sensor exceeding a threshold.

18. The system of claim 11, wherein the purging condition includes the engine being in an engine-on mode of operation, and a canister pressure being greater than a threshold.

19. A vehicle fuel vapor recovery system, comprising,

a fuel tank coupled to a canister through a fuel tank isolation valve, the fuel tank configured to receive fuel through a refueling door;

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

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 operation,

opening the canister purge valve while closing the fuel tank isolation valve to purge a first amount of stored fuel vapors to the engine intake when the canister pressure is greater than a threshold;

after purging the first amount of stored fuel vapors, opening the fuel tank isolation valve while closing the canister purge valve to purge a second amount of fuel vapors to the canister when the fuel tank pressure is greater than a first threshold; and

after purging the first amount of stored fuel vapors, opening the fuel tank isolation valve while maintaining the canister purge valve open to purge the second amount of fuel vapors to the engine intake when the fuel tank pressure is greater than a second threshold higher than the first threshold.

20. The system of claim 19, wherein the control system further includes instructions for, in response to a request for refueling, delaying purging until refueling is completed, a completion of refueling indicated by a closing of the refueling door.

21. The system of claim 20, wherein a duration of delaying is adjusted based on a fuel level in the fuel tank and/or a fuel tank pressure after refueling, including delaying purging for a longer duration as the fuel level and/or the fuel tank pressure increase during refueling.