HYBRID VEHICLE FUEL SYSTEM LEAK DETECTION

• US 20140316638A1
• Filed: 04/17/2013
• Published: 10/23/2014
• Est. Priority Date: 04/17/2013
• Status: Active Grant

• Current Assignee: Ford Global Technologies, LLC (Ford Motor Company)
• Original Assignee: Ford Global Technologies, LLC (Ford Motor Company)
• Inventors: Dudar, Aed M., Peters, Mark W., Yang, Dennis Seung-Man
• Granted Patent: US 9,322,342 B2
• Time in Patent Office: Days
• US Class Current: 701/29.4
• CPC Class Codes: F02D 29/02 peculiar to engines driving vehicles; peculiar to engines driving variable pitch propellers
• CPC Class Codes: F02M 25/0809 Judging failure of purge control system

Abstract

Methods and systems for fuel system leak detection in a hybrid electric vehicle using a fuel reservoir are disclosed. In one example approach, a method comprises, during an engine off condition, delivering fuel from a fuel tank into a reservoir while the fuel tank is vented to atmosphere, and sealing the fuel tank from atmosphere and indicating a leak based on pressure in the fuel tank.

Claims

1. A method for a vehicle with an engine, comprising:

during an engine off condition, delivering fuel from a fuel tank into a reservoir while the fuel tank is vented to atmosphere; and

sealing the fuel tank from atmosphere and indicating a leak based on pressure in the fuel tank.

2. The method of claim 1, wherein delivering fuel from the fuel tank into a reservoir comprises operating a fuel pump for a duration while the fuel tank is vented to the atmosphere, and wherein the delivering fuel from the fuel tank into the reservoir occurs while the reservoir is sealed from the fuel tank such that the reservoir is at a different internal pressure than the fuel tank.

3. The method of claim 1, further comprising:

opening a fuel tank isolation valve to vent the fuel tank to the atmosphere while delivering fuel from the fuel tank into the reservoir; and

closing the fuel tank isolation valve and discontinuing delivery of fuel from the fuel tank into the reservoir after a duration to generate engine-off pressure in the fuel tank for leak diagnostics.

4. The method of claim 1, wherein the reservoir is located inside of the fuel tank.

5. The method of claim 1, wherein the vehicle is a hybrid electric vehicle.

6. The method of claim 1, further comprising indicating a leak in response to a pressure increase less than a threshold while the fuel tank is sealed from atmosphere.

7. The method of claim 1, further comprising:

during an engine off condition, delivering fuel from the fuel tank into the reservoir for a duration while the fuel tank is sealed from atmosphere; and

indicating a leak based on vacuum in the fuel tank.

8. The method of claim 7, further comprising:

closing a fuel tank isolation valve to seal the fuel tank from the atmosphere while delivering fuel from the fuel tank into the reservoir; and

discontinuing delivery of fuel from the fuel tank into the reservoir after the duration to generate engine-off vacuum in the fuel tank for leak diagnostics.

9. The method of claim 7, further comprising indicating a leak in response to a vacuum increase less than a threshold while the fuel tank is sealed from atmosphere.

10. A method for a vehicle with an engine with a fuel system, comprising:

during a first engine off condition, delivering fuel from a fuel tank into a reservoir to generate pressure for leak diagnostics; and

during a second engine off condition, delivering fuel from the fuel tank into the reservoir to generate vacuum for leak diagnostics.

11. The method of claim 10, further comprising:

during the first engine off condition operating a fuel pump to deliver fuel from the fuel tank into the reservoir while the fuel tank is vented to atmosphere and then sealing the fuel tank from atmosphere and indicating a leak based on a pressure increase in the fuel tank; and

during the second engine off condition operating the fuel pump to deliver fuel from the fuel tank into the reservoir while the fuel tank is sealed from the atmosphere and indicating a leak based on a pressure decrease in the fuel tank.

12. The method of claim 10, further comprising indicating a degradation in the fuel system of the vehicle in response to both an indication of a leak based on pressure generated in the fuel tank during the first engine off condition and an indication of a leak based on vacuum generated in the fuel tank during the second condition.

13. The method of claim 10, further comprising:

during the first engine off condition opening a fuel tank isolation valve and operating a fuel pump to deliver fuel from the fuel tank into the reservoir and then closing the fuel tank isolation valve and discontinuing operation of the fuel pump and indicating a leak based on a pressure increase in the fuel tank less than a pressure increase threshold after operation of the fuel pump is discontinued; and

during the second engine off condition closing the fuel tank isolation valve and operating the fuel pump to deliver fuel from the fuel tank into the reservoir and then discontinuing operation of the fuel pump and indicating a leak based on a vacuum increase in the fuel tank less than a vacuum increase threshold after operation of the fuel pump is discontinued.

14. The method of claim 10, wherein the reservoir is located inside of the fuel tank.

15. The method of claim 10, wherein the vehicle is a hybrid electric vehicle.

16. The method of claim 10, wherein during the first engine off condition, a first amount of fuel is delivered from the fuel tank into the reservoir and the method further comprises returning the first amount of fuel to the fuel tank after generating pressure for leak diagnostics, and wherein, during the second engine off condition, a second amount of fuel is delivered from the fuel tank into the reservoir and the method further comprises returning the second amount of fuel to the fuel tank after generating vacuum for leak diagnostics.

17. A vehicle system, comprising:

a fuel system including a fuel tank and a fuel vapor canister;

a fuel reservoir;

a fuel pump;

a fuel tank isolation valve; and

a controller configured to;

during a first engine off condition;

open the fuel tank isolation valve and operate the fuel pump to deliver fuel from the fuel tank into the reservoir;

close the fuel tank isolation valve and discontinue operation of the fuel pump; and

indicate a leak based on a pressure increase in the fuel tank less than a pressure increase threshold after operation of the fuel pump is discontinued; and

during a second engine off condition;

close the fuel tank isolation valve and operate the fuel pump to deliver fuel from the fuel tank into the reservoir; and

discontinue operation of the fuel pump and indicate a leak based on a vacuum increase in the fuel tank less than a vacuum increase threshold after operation of the fuel pump is discontinued.

18. The system of claim 17, further comprising indicating a degradation in the fuel system of the vehicle only in response to both an indication of a leak based on pressure generated in the fuel tank during the first engine off condition and an indication of a leak based on vacuum generated in the fuel tank during the second condition.

19. The system of claim 17, wherein the reservoir is located inside of the fuel tank.

20. The system of claim 17, wherein the vehicle system is a plug-in hybrid electric vehicle.