SYSTEM AND METHODS FOR FUEL SYSTEM RECIRCULATION TUBE DIAGNOSTIC

• US 20170198662A1
• Filed: 01/12/2016
• Published: 07/13/2017
• Est. Priority Date: 01/12/2016
• 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.
• Granted Patent: US 9,989,018 B2
• Time in Patent Office: Days
• 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 15/04 Tank inlets B60K15/077 takes precedence
• CPC Class Codes: B60K 2015/03447 for improving the sealing
• CPC Class Codes: B60K 2015/03514 with vapor recovery means
• CPC Class Codes: B60K 2015/03538 the venting tube being connected with the filler tube
• CPC Class Codes: B60K 2015/0461 comprising a filler pipe shutter, e.g. trap, door or flap for fuel inlet
• CPC Class Codes: B60K 6/20 the prime-movers consisting of electric motors and internal combustion engines, e.g. HEVs
• CPC Class Codes: F02D 41/0042 Controlling the combustible mixture as a function of the canister purging, e.g. control of injected fuel to compensate for deviation of air fuel ratio when purging
• CPC Class Codes: F02D 41/0045 Estimating, calculating or determining the purging rate, amount, flow or concentration
• CPC Class Codes: F02M 25/0809 Judging failure of purge control system
• CPC Class Codes: F02M 25/0818 having means for pressurising the evaporative emission space
• CPC Class Codes: F02M 25/0836 Arrangement of valves controlling the admission of fuel vapour to an engine, e.g. valve being disposed between fuel tank or absorption canister and intake manifold
• CPC Class Codes: F02M 25/0854 Details of the absorption canister
• CPC Class Codes: F02M 37/0082 Devices inside the fuel tank other than fuel pumps or filters electrical pumps submerged in fuel tanks F02M37/10, jet pumps F02M37/025

Abstract

Methods and systems are provided for indicating restrictions in a fuel system vapor recirculation line. In one example, a fuel tank is evacuated responsive to a fuel level below a threshold, and if the vacuum is relieved via a negative pressure relief valve in a capless fuel filler system, the negative pressure relief valve is indicated to be functional such that, responsive to a fuel level greater than a threshold, the fuel system may be evacuated and a restriction may be indicated in the vapor recirculation line responsive to the negative pressure valve not relieving the applied vacuum. In this way, restrictions in the vapor recirculation line may be rapidly diagnosed and excessive loading of a fuel vapor canister may be prevented, thus reducing the potential for evaporative emissions being released to the atmosphere and prolonging fuel vapor canister function.

Claims

1. A method comprising:

responsive to a fuel tank fill level below a first threshold, applying vacuum to the fuel system to generate a first fuel system pressure profile;

responsive to a fuel tank fill level above a second threshold, applying vacuum to the fuel system to generate a second fuel system pressure profile; and

indicating a restriction in a vapor recirculation line based on the first and second fuel system pressure profiles.

2. The method of claim 1, wherein:

the fuel tank is coupled in a fuel system within a vehicle, wherein the pressure profiles are pressure profiles over time, and wherein the fuel tank is coupled to a fuel filler neck via a spud valve, the fuel filler neck coupled to a negative pressure relief valve;

taking an action in response to the indicated restriction; and

wherein the first threshold level comprises a fuel level below the spud valve, and wherein the second threshold level comprises a fuel level above the spud valve, wherein the fuel tank fill level below a first threshold comprises a first condition and the fuel tank fill level above the second threshold comprises a second, different, condition, wherein none of the pressure profile of the first condition overlaps a duration of the pressure profile of the second condition.

3. The method of claim 2, wherein indicating a restriction in the vapor recirculation line further comprises:

indicating a restriction responsive to both the first fuel system pressure profile including a vacuum relief inflection point during applying vacuum in the first condition, and the second fuel system pressure profile not including a vacuum relief inflection point during applying vacuum in the second condition.

4. The method of claim 2, wherein the first condition further comprises:

routing vacuum through the fuel tank to the negative pressure relief valve via the fuel filler neck.

5. The method of claim 2, wherein the second condition further comprises:

routing vacuum to the negative pressure relief valve via the vapor recirculation line.

6. The method of claim 3, further comprising:

indicating the negative pressure relief valve is functional responsive to an indication of a vacuum relief inflection point during applying vacuum in the first condition; and

indicating an absence of restriction in the vapor recirculation line responsive to an indication of a vacuum relief inflection point during applying the vacuum in the second condition, wherein it was previously indicated that the negative pressure relief valve is functional.

7. The method of claim 3, wherein during applying vacuum during both the first condition and the second condition, the vacuum relief inflection point corresponding to the first fuel system pressure profile and the vacuum relief inflection point corresponding to the second fuel system pressure profile indicates opening of the negative pressure relief valve.

8. The method of claim 7, wherein both the first condition and the second condition further comprise:

stopping applying vacuum and relieving fuel system vacuum to atmosphere if a threshold vacuum level is reached, the threshold vacuum level comprising a vacuum level greater than a level expected to actuate the negative pressure relief valve.

9. The method of claim 3, further comprising:

fluidically coupling the fuel system to a fuel vapor canister configured within an evaporative emissions control system by opening a fuel tank isolation valve; and

wherein applying vacuum to the fuel system includes opening the fuel tank isolation valve, and activating a vacuum pump positioned within a vent line between the fuel vapor canister and atmosphere to draw vacuum on the evaporative emissions control system and fuel system.

10. The method of claim 9, further comprising:

prior to applying vacuum on the fuel system,

indicating a reference vacuum level by applying vacuum via the vacuum pump to a reference orifice; and

during applying vacuum on the fuel system;

indicating undesired evaporative emissions responsive to a fuel system vacuum level less than the reference vacuum level after a predetermined time period.

11. The method of claim 10, further comprising:

responsive to an indication of the fuel system vacuum greater than or equal to the reference vacuum level after a predetermined time period;

maintaining applying vacuum on the fuel system during the first condition and the second condition.

12. A method comprising:

during evacuating an evaporative emissions control system and fuel system to conduct an evaporative emissions test with an onboard vacuum pump;

monitoring pressure in the evaporative emissions control system and fuel system; and

responsive to an indication of an absence of undesired evaporative emissions;

in a first condition, including a fuel level in a fuel tank below a first threshold level, maintaining evacuating the evaporative emissions control system and fuel system and indicating a negative pressure relief valve in a capless fuel filler system is functional responsive to a vacuum relief inflection point; and

in a second condition, including the fuel level in the fuel tank above a second threshold level and an indication that the negative pressure relief valve is functional, maintaining evacuating the evaporative emissions control system and fuel system and indicating a restriction in a fuel system vapor recirculation line responsive to an absence of a vacuum relief inflection point.

13. The method of claim 12, further comprising:

fluidically coupling the fuel tank to the negative pressure relief valve in the capless fuel filler system via a fuel filler neck, the fuel filler neck coupled to the fuel tank via a spud valve; and

wherein the first threshold level comprises the fuel level below the spud valve, and wherein the second threshold level comprises the fuel level above the spud valve.

14. The method of claim 13, wherein the first condition includes routing vacuum to the negative pressure relief valve via the fuel filler neck through the spud valve, the fuel filler neck comprising a less restrictive path to the negative pressure relief valve than a path through the fuel system vapor recirculation line.

15. The method of claim 12, wherein the second condition includes routing vacuum to the negative pressure relief valve via the fuel system vapor recirculation line.

16. The method of claim 12, further comprising:

prior to evacuating the evaporative emissions control system and fuel system to conduct an evaporative emissions test;

activating the onboard vacuum pump;

drawing a vacuum across a reference orifice;

determining a reference vacuum level; and

wherein during evacuating the evaporative emissions control system and fuel system, an indication of an absence of undesired evaporative emissions includes attaining a vacuum level in the evaporative emissions control system and fuel system equal to or greater than the reference vacuum level after a predetermined time period.

17. The method of claim 12, wherein both the first and the second conditions further comprise:

stopping maintaining evacuating the evaporative emissions control system and fuel system responsive to the vacuum level in the evaporative emissions control system and fuel system reaching a second threshold vacuum level, wherein a vacuum relief inflection point in both the first condition and the second condition is not indicated, the vacuum relief inflection point in both the first condition and the second condition comprising opening of the negative pressure relief valve.

18. The method of claim 17, wherein the second threshold vacuum level comprises a vacuum level greater than a level of vacuum expected to open the negative pressure relief valve.

19. A system for a vehicle, comprising:

a fuel tank configured within a fuel system;

a fuel vapor canister, configured within an evaporative emissions control system, coupled to the fuel tank via a fuel tank isolation valve, and coupled to atmosphere via a canister vent valve positioned in a vent line;

a vacuum pump positioned between the fuel vapor canister and the canister vent valve within the vent line;

a fuel filler neck coupling the fuel tank to a capless fuel filler system via a spud valve;

a negative pressure relief valve coupled within the capless fuel filler system;

a fuel level sensor;

a fuel tank pressure transducer;

a fuel vapor recirculation line coupling the fuel tank to the capless fuel filler system;

a controller storing instructions in non-transitory memory, that when executed, cause the controller to;

determine a reference vacuum threshold by drawing a vacuum via the vacuum pump on a reference orifice;

evacuate the evaporative emissions control system and fuel system by commanding open the fuel tank isolation valve, commanding open the canister vent valve, and activating the vacuum pump;

indicate an absence of undesired evaporative emissions responsive to a vacuum build equal to or greater than the reference vacuum threshold as monitored by the fuel tank pressure transducer;

indicate a fuel level in the fuel tank via the fuel level sensor;

maintain evacuating the evaporative emissions control system and fuel system responsive to an indication of the absence of undesired evaporative emissions and whether the fuel level is below a first threshold or above a second threshold, the first threshold comprising the fuel level below the spud valve, and the second threshold comprising the fuel level above the spud valve; and

in a first condition, including the fuel level below the first threshold, indicate a first fuel system pressure profile during maintaining evacuating the evaporative emissions control system and fuel system;

in a second condition, including the fuel level above the second threshold, indicate a second fuel system pressure profile during maintaining evacuating the evaporative emissions control system and fuel system; and

indicate a restriction in the vapor recirculation line based on the first and second fuel system pressure profiles.

20. The system of claim 19, wherein the controller further stores instructions in non-transitory memory, that when executed, cause the controller to:

indicate a restriction in the vapor recirculation line responsive to both the first fuel system pressure profile including a vacuum relief inflection point during maintaining evacuating the evaporative emissions control system and fuel system in the first condition, and the second fuel system pressure profile not including a vacuum relief inflection point during maintaining evacuating the evaporative emissions control system and fuel system in the second condition;

wherein the vacuum relief inflection point in both the first and second conditions includes opening of the negative pressure relief valve; and

wherein the first condition includes routing vacuum through the fuel tank to the negative pressure relief valve via the fuel filler neck, and wherein the second condition includes routing vacuum to the negative pressure relief valve via the vapor recirculation line.