SYSTEMS AND METHODS FOR DETERMINING THE INTEGRITY OF A VEHICLE FUEL SYSTEM

• US 20150198123A1
• Filed: 01/14/2014
• Published: 07/16/2015
• Est. Priority Date: 01/14/2014
• Status: Active Grant

• Current Assignee: Ford Global Technologies, LLC (Ford Motor Company)
• Original Assignee: Ford Global Technologies, LLC (Ford Motor Company)
• Inventors: Pearce, Russell Randall, Peters, Mark W., Dudar, Aed M., Yang, Dennis Seung-Man
• Granted Patent: US 9,669,705 B2
• Time in Patent Office: Days
• US Class Current: 1/1
• CPC Class Codes: B60K 15/03504 adapted to avoid loss of fuel or fuel vapour, e.g. with vapour recovery systems
• CPC Class Codes: F02D 2041/225 Leakage detection
• CPC Class Codes: F02D 41/22 Safety or indicating devices for abnormal conditions in air/fuel ratio feedback systems F02D41/1495, in electric control linkage F02D11/107, in purge control systems F02M25/0809
• CPC Class Codes: F02M 25/0809 Judging failure of purge control system

Abstract

A method, comprising: indicating leakage on a canister side of a fuel system based on a first fuel system pressure following applying a vacuum to the fuel system with a fuel tank isolation valve closed; and indicating leakage on a fuel tank side of the fuel system based on the first fuel system pressure and a second fuel system pressure following applying a vacuum to the fuel system with the fuel tank isolation valve open. In this way, an ELCM with a single reference orifice may be used to perform a leak test with two different thresholds for leak detection. This may allow vehicles currently in production to meet future emissions standards without costly upgrades to the ELCM.

Claims

1. A method, comprising:

indicating leakage on a canister side of a fuel system based on a first fuel system pressure following applying a vacuum to the fuel system with a fuel tank isolation valve closed; and

indicating leakage on a fuel tank side of the fuel system based on the first fuel system pressure and a second fuel system pressure following applying a vacuum to the fuel system with the fuel tank isolation valve open.

2. The method of claim 1, where indicating leakage on the canister side of the fuel system further comprises:

determining a reference pressure by applying a vacuum to a reference orifice; and

dividing the first fuel system pressure by the reference pressure to establish a canister side threshold value.

3. The method of claim 2, further comprising:

determining a size of a leak on the canister side of the fuel system based on a diameter of the reference orifice and the canister side threshold value.

4. The method of claim 2, where indicating leakage on the fuel tank side of the fuel system further comprises:

dividing the second fuel system pressure by the reference pressure to establish a system threshold value; and

determining a size of a leak on the fuel tank side of the fuel system based on the system threshold value and the canister side threshold value.

5. The method of claim 1, further comprising:

purging stored fuel vapors from a fuel vapor canister to a fuel tank by maintaining the fuel tank isolation valve open following cessation of applying a vacuum to the fuel system with the fuel tank isolation valve open.

6. The method of claim 5, further comprising:

closing the fuel tank isolation valve responsive to a fuel tank pressure increasing to atmospheric pressure.

7. A method for an evaporative emissions system leak test, comprising:

determining a reference vacuum threshold;

determining a first fuel system pressure by drawing a vacuum on a fuel system with a fuel tank isolation valve closed;

generating a canister threshold value based on the first fuel system pressure and the reference vacuum threshold;

indicating a leak based on the canister threshold value;

determining a second fuel system pressure by drawing a vacuum on the fuel system with the fuel tank isolation valve open;

generating a fuel system threshold value based on the second fuel system pressure and the reference vacuum threshold; and

indicating a leak based on the fuel system threshold value and the canister threshold value.

8. The method of claim 7, where determining the reference vacuum threshold further comprises:

isolating an evaporative leak check module from a fuel tank;

activating a vacuum pump comprising the evaporative leak check module;

drawing a vacuum across a reference orifice; and

determining a reference vacuum in the evaporative leak check module.

9. The method of claim 8, where determining a first fuel system pressure further comprises:

opening a canister vent valve; and

coupling the vacuum pump to both atmosphere and the fuel system.

10. The method of claim 9, where coupling the vacuum pump to both atmosphere and the fuel system further comprises:

moving a changeover valve within the evaporative leak check module from a first position to a second position.

11. The method of claim 10, further comprising:

responsive to the second fuel system pressure being less than a purge vacuum threshold, maintaining the fuel tank isolation valve open;

maintaining the canister vent valve open;

maintaining the changeover valve in the second position;

deactivating the vacuum pump; and

purging stored fuel vapor from a fuel vapor canister to the fuel tank.

12. The method of claim 11, further comprising:

responsive to a fuel tank pressure increasing to atmospheric pressure, closing the fuel tank isolation valve;

shifting the changeover valve to the first position; and

closing the canister vent valve.

13. A fuel system for a vehicle, comprising:

a fuel tank;

a fuel vapor canister coupled to the fuel tank via a fuel tank isolation valve;

an evaporative leak check module coupled to the fuel vapor canister via a canister vent valve; and

a control system including executable instructions stored in non-transitory memory for;

determining a reference vacuum threshold;

determining a first fuel system pressure by drawing a vacuum on the fuel system with the fuel tank isolation valve closed;

generating a canister threshold value based on the first fuel system pressure and the reference vacuum threshold;

indicating a leak based on the canister threshold value;

determining a second fuel system pressure by drawing a vacuum on the fuel system with the fuel tank isolation valve open;

generating a fuel system threshold value based on the second fuel system pressure and the reference vacuum threshold; and

indicating a leak based on the fuel system threshold value and the canister threshold value.

14. The fuel system of claim 13, where the evaporative leak check module comprises:

a vacuum pump;

a changeover valve movable between a first position and a second position;

a reference orifice;

a pressure sensor; and

where determining a reference vacuum threshold further comprise;

closing the canister vent valve;

placing the changeover valve in the first position;

activating the vacuum pump;

drawing a vacuum across the reference orifice; and

measuring an internal pressure in the evaporative leak check module.

15. The fuel system of claim 14, where determining a first fuel system pressure further comprises:

opening the canister vent valve;

placing the changeover valve in the second position;

then

activating the vacuum pump.

16. The fuel system of claim 15, where determining a second fuel system pressure further comprises:

maintaining the canister vent valve open; and

maintaining the changeover valve in the second position.

17. The fuel system of claim 14, where the control system further includes executable instructions stored in non-transitory memory for:

responsive to the second fuel system pressure being less than a purge vacuum threshold, maintaining the fuel tank isolation valve open;

maintaining the canister vent valve open;

maintaining the changeover valve in the second position;

deactivating the vacuum pump; and

purging stored fuel vapor from a fuel vapor canister to the fuel tank.

18. The fuel system of claim 17, where the control system further includes executable instructions stored in non-transitory memory for:

responsive to a fuel tank pressure increasing to atmospheric pressure, closing the fuel tank isolation valve;

shifting the changeover valve to the first position; and

closing the canister vent valve.

19. The fuel system of claim 14, where the control system further includes executable instructions stored in non-transitory memory for:

indicating a leak with a diameter less than the diameter of the reference orifice based on the fuel system threshold value and the canister threshold value.

20. The fuel system of claim 19, where the reference orifice comprises a diameter of 0.017″

.