SYSTEMS AND METHODS FOR DETERMINING CANISTER PURGE VALVE DEGRADATION

• US 20160160808A1
• Filed: 12/04/2014
• Published: 06/09/2016
• Est. Priority Date: 12/04/2014
• 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 9,416,755 B2
• Time in Patent Office: Days
• CPC Class Codes: F02D 35/0015 using exhaust gas sensors F02D41/14 takes precedence
• CPC Class Codes: F02D 41/003 Adding fuel vapours, e.g. drawn from engine fuel reservoir
• CPC Class Codes: F02D 41/004 Control of the valve or purge actuator, e.g. duty cycle, closed loop control of position
• CPC Class Codes: F02D 41/26 using computer, e.g. microprocessor
• CPC Class Codes: F02M 25/0809 Judging failure of purge control system
• 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

Abstract

A method is provided, comprising: during a first condition, opening a fuel tank isolation valve while maintaining a canister purge valve closed; and indicating degradation of the canister purge valve based on an output of a universal exhaust gas oxygen (UEGO) sensor. The UEGO sensor output will indicate whether any fuel vapor vented from the fuel tank reaches intake through the commanded closed canister purge valve. In this way, canister purge valve degradation may be diagnosed in vehicles that do not include a functional fuel tank pressure sensor or canister vent valve.

Claims

1. A method, comprising:

during a first condition, opening a fuel tank isolation valve while maintaining a canister purge valve closed; and

indicating degradation of the canister purge valve based on an output of a universal exhaust gas oxygen (UEGO) sensor.

2. The method of claim 1, wherein the first condition comprises a lean engine diagnostic code.

3. The method of claim 2, wherein indicating degradation of the canister purge valve based on the output of the UEGO sensor comprises indicating degradation of the canister purge valve responsive to the UEGO sensor indicating a threshold decrease in exhaust gas oxygen.

4. The method of claim 3, further comprising:

indicating an intact canister purge valve responsive to the UEGO sensor not indicating a threshold decrease in exhaust gas oxygen.

5. The method of claim 3, wherein the threshold decrease in exhaust gas oxygen is based on one or more operating conditions.

6. The method of claim 5, wherein the one or more operating conditions include a fuel composition.

7. The method of claim 5, wherein the one or more operating conditions do not include a fuel tank pressure.

8. The method of claim 7, further comprising:

maintaining the fuel tank isolation valve closed until the fuel tank isolation valve closed duration increases above a threshold.

9. The method of claim 1, further comprising:

adjusting a commanded air/fuel ratio responsive to the indication of degradation of the canister purge valve.

10. A fuel system for a vehicle, comprising:

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

an engine intake coupled to the fuel vapor canister via a canister purge valve;

an universal exhaust gas oxygen (UEGO) sensor coupled to an engine exhaust; and

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

responsive to an engine lean code, open the fuel tank isolation valve while maintaining the canister purge valve closed; and

indicate degradation of the canister purge valve based on an output of the UEGO sensor.

11. The fuel system of claim 10, wherein the fuel vapor canister is coupled to atmosphere via a vent line, the vent line not comprising a canister vent valve.

12. The fuel system of claim 10, wherein the fuel tank is not coupled to a fuel tank pressure sensor.

13. The fuel system of claim 10, wherein the controller is further configured with instructions stored in non-transitory memory, that when executed, cause the controller to:

establish a UEGO sensor output threshold based on one or more operating conditions; and

indicate degradation of the canister purge valve responsive to the UEGO sensor output decreasing below the threshold.

14. The fuel system of claim 13, wherein the controller is further configured with instructions stored in non-transitory memory, that when executed, cause the controller to:

indicate an intact canister purge valve responsive to the UEGO sensor output not decreasing below the threshold.

15. The fuel system of claim 13, where the one or more operating conditions include a fuel composition.

16. The fuel system of claim 13, where the one or more operating conditions include a fuel level.

17. The fuel system of claim 13, where the one or more operating conditions do not include a fuel tank pressure.

18. The fuel system of claim 10, wherein the controller is further configured with instructions stored in non-transitory memory, that when executed, cause the controller to:

open the fuel tank isolation valve responsive to a fuel tank isolation valve closed duration being greater than a threshold.

19. The fuel system of claim 10, wherein the fuel vapor canister comprises a fuel vapor canister buffer, and wherein the fuel tank is coupled to a load port of the fuel vapor canister buffer.

20. A method for a fuel system, comprising:

responsive to a lean engine diagnostic code, maintaining a fuel tank isolation valve closed for a threshold duration;

opening the fuel tank isolation valve while maintaining a canister purge valve closed;

establishing a threshold output of an universal exhaust gas oxygen (UEGO) sensor based on one or more operating conditions;

indicating degradation of the canister purge valve responsive to the output of the UEGO sensor decreasing below the threshold; and

closing the fuel tank isolation valve.