SYSTEMS AND METHODS FOR DETECTION AND MITIGATION OF LIQUID FUEL CARRYOVER IN AN EVAPORATIVE EMISSIONS SYSTEM

• US 20170008390A1
• Filed: 07/09/2015
• Published: 01/12/2017
• Est. Priority Date: 07/09/2015
• 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., Yang, Dennis Seung-Man, Ognjanovski, Robert Jr., Pearce, Russell Randall
• Granted Patent: US 10,006,413 B2
• Time in Patent Office: Days
• US Class Current: 1/1
• CPC Class Codes: B60K 15/03 Fuel tanks chassis frame comprising fluid storage compartment B62D21/16 ; Details of the fuel feeding system related to the fuel tank F02M37/0076
• CPC Class Codes: B60K 15/03006 Gas tanks B60K15/07 takes precedence
• CPC Class Codes: B60K 2015/03019 Filling of gas tanks
• 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 2015/0321 characterised by special sensors, the mounting thereof
• CPC Class Codes: B60K 2015/03217 Fuel level sensors
• CPC Class Codes: B60K 2015/03243 characterised by special pumps, the mounting thereof
• CPC Class Codes: B60K 2015/03256 characterised by special valves, the mounting thereof
• CPC Class Codes: B60K 2015/03328 Arrangements or special measures related to fuel tanks or fuel handling
• CPC Class Codes: B60K 2015/03514 with vapor recovery means
• CPC Class Codes: B60K 2015/03566 comprising means for stopping the venting of fuel vapor, e.g. during refueling or engine stop
• CPC Class Codes: F02D 41/003 Adding fuel vapours, e.g. drawn from engine fuel reservoir
• CPC Class Codes: F02M 25/0818 having means for pressurising the evaporative emission space
• CPC Class Codes: F02M 25/0872 Details of the fuel vapour pipes or conduits

Abstract

Methods and systems are provided for detecting and mitigating the presence of liquid fuel carryover in an evap system of a vehicle in response to a refueling event. In one example, during a first condition, a vacuum pump is activated to pressurize the fuel system responsive to a first fuel tank pressure decay rate being less than a threshold, and responsive to a second fuel tank pressure decay rate being greater than a threshold, the vacuum pump is maintained on until a fuel tank pressure decreases to atmospheric pressure. In this way, liquid fuel carryover can be quickly and accurately diagnosed, such that mitigating actions may be taken to ensure liquid fuel is returned to the tank prior to contacting the adsorbent material within the vapor canister.

Claims

1. A method for a fuel system, comprising:

during a first condition, activating a vacuum pump to pressurize the fuel system responsive to a first fuel tank pressure decay rate being less than a threshold; and

responsive to a second fuel tank pressure decay rate being greater than a threshold, maintaining the vacuum pump on until a fuel tank pressure decreases to atmospheric pressure.

2. The method of claim 1, wherein the first condition includes a fuel tank isolation valve in an open conformation.

3. The method of claim 2, wherein the fuel tank isolation valve was opened prior to a recently completed refueling event.

4. The method of claim 3, further comprising:

responsive to a second fuel tank pressure decay rate being greater than a threshold, determining whether the recently completed refueling event included an automatic shutoff of a refueling dispenser; and

responsive to determining that the recently completed refueling event did not include an automatic shutoff of a refueling dispenser, indicating to perform one or more on-board tests to determine the integrity of the fuel system.

5. The method of claim 4, further comprising:

responsive to determining that the recently completed refueling event did include an automatic shutoff of a refueling dispenser, determining whether a fuel level indicator indicates that a fuel tank is full; and

responsive to determining that the fuel level indicator indicates that the fuel tank is full, indicating that the fuel tank was overfilled.

6. The method of claim 5, further comprising:

responsive to determining that the fuel level indicator indicates that the fuel tank is not full, indicating an on-board test to determine the integrity of the fuel level indicator.

7. The method of claim 1, further comprising:

responsive to the second fuel tank pressure decay rate being less than the threshold, deactivating the vacuum pump; and

indicating a restriction in an evaporative emissions system coupled to the fuel system.

8. The method of claim 7, further comprising:

responsive to indicating a restriction in an evaporative emissions system, suspending a canister purge operation at a subsequent engine-on event.

9. A method for a fuel system, comprising:

following a refueling event, monitoring a fuel tank pressure bleed-down rate;

indicating the presence of liquid fuel in an evap recovery line responsive to a first fuel tank pressure bleed-down rate less than a threshold; and

actively returning the liquid fuel in the evap recovery line to the fuel tank.

10. The method of claim 9, wherein actively returning the liquid fuel in the evap recovery line to the fuel tank comprises:

maintaining a fuel tank isolation valve open; and

activating an evaporative leak check module vacuum pump in a pressurizing mode.

11. The method of claim 10, further comprising:

maintaining the evaporative leak check module vacuum pump on in the pressurizing mode responsive to a second fuel tank pressure bleed-down rate greater than a threshold; and

deactivating the evaporative leak check module vacuum pump responsive to a fuel tank pressure decreasing to atmospheric pressure.

12. The method of claim 11, further comprising:

closing the fuel tank isolation valve responsive to the fuel tank pressure decreasing to atmospheric pressure.

13. The method of claim 11, further comprising:

deactivating the evaporative leak check module vacuum pump responsive to the second fuel tank pressure bleed-down rate being less than a threshold; and

indicating a restriction in the evap recovery line.

14. The method of claim 13, further comprising:

responsive to indicating a restriction in the evap recovery line, suspending a canister purge operation at a subsequent engine-on event.

15. The method of claim 9, wherein the refueling event comprises one or more automatic shutoffs of a refueling dispenser.

16. The method of claim 9, further comprising:

monitoring a fuel tank pressure and a fuel tank fill level during the refueling event.

17. The method of claim 9, further comprising:

responsive to the first fuel tank pressure bleed-down rate being greater than the threshold, sealing the fuel tank responsive to a fuel tank pressure decreasing to atmospheric pressure; and

updating a canister purge schedule.

18. A fuel system, comprising:

a fuel tank coupled to a fuel vapor canister via one or more evap recovery lines;

a fuel tank isolation valve coupled between the fuel tank and the fuel vapor canister;

a fuel tank pressure sensor;

a fuel tank fill level sensor; and

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

receive a request for a refueling event;

open the fuel tank isolation valve;

monitor a fuel tank pressure via the fuel tank pressure sensor and a fuel tank fill level via the fuel tank fill level sensor for the duration of the refueling event;

indicate liquid fuel carryover into the one or more evap recovery lines responsive to a first fuel tank pressure decay rate following the refueling event being less than a threshold.

19. The fuel system of claim 18, further comprising:

an evaporative leak check module comprising a reversible vacuum pump coupled between the fuel vapor canister and atmosphere; and

wherein the controller further stores instructions in non-transitory memory, that when executed, cause the controller to;

responsive to an indication of liquid fuel carryover into the one or more evap recovery lines, activate the reversible vacuum pump to direct atmospheric air into the fuel system; and

maintain the reversible vacuum pump on responsive to a second fuel tank pressure decay rate being greater than a threshold.

20. The fuel 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 one or more evap recovery lines responsive to the second fuel tank pressure decay rate being less than the threshold.