SYSTEMS AND METHODS FOR ENGINE-OFF NATURAL VACUUM LEAK TESTING

• US 20160186695A1
• Filed: 04/15/2015
• Published: 06/30/2016
• Est. Priority Date: 12/30/2014
• Status: Active Application

• Current Assignee: Ford Global Technologies, LLC (Ford Motor Company)
• Original Assignee: Ford Global Technologies, LLC (Ford Motor Company)
• Inventors: Dudar, Aed M., Liu, Chingpo, Yang, Dennis Seung-Man, Jentz, Robert Roy, Tseng, Fling Finn, Makki, Imad Hassan, Pearce, Russell Randall
• Granted Patent: US 10,273,907 B2
• Time in Patent Office: Days
• US Class Current: 1/1
• CPC Class Codes: F02M 25/0809 Judging failure of purge control system

Abstract

A method is provided, comprising terminating a pressure rise portion of an engine-off natural vacuum test based on an initial rate of change of a fuel system pressure upon sealing a fuel system; and initiating a vacuum portion of the engine-off natural vacuum test responsive to suspending the pressure rise portion. The initial rate of change may indicate a likelihood of the pressure rise portion reaching a pressure rise threshold. In this way, the vacuum portion of the test may be initiated earlier, increasing the likelihood of a conclusive result being obtained during a test time limit.

Claims

1. A method, comprising:

terminating a pressure rise portion of an engine-off natural vacuum test based on an initial rate of change of a fuel system pressure upon sealing a fuel system; and

initiating a vacuum portion of the engine-off natural vacuum test responsive to suspending the pressure rise portion.

2. The method of claim 1, further comprising:

indicating degradation of the fuel system based on a comparison of a fuel tank vacuum and a threshold.

3. The method of claim 2, wherein the threshold is adjusted based on a heat rejection index, the heat rejection index indicative of an amount of heat transferred to the fuel system during a previous drive cycle.

4. The method of claim 3, wherein the heat rejection index is based on a time-weighted driving aggressiveness index.

5. The method of claim 3, wherein the heat rejection index is based on a resistance of a heating element of a heated exhaust gas oxygen sensor.

6. The method of claim 1, wherein the initial rate of change of the fuel system pressure is determined based on a fuel system pressure change between sealing of the fuel system, and a subsequent inflection point in a fuel system pressure profile.

7. The method of claim 6, further comprising:

fitting the fuel system pressure profile to a polynomial;

determining a likelihood of the fuel system pressure reaching a pressure threshold; and

terminating the pressure rise portion of the engine-off natural vacuum test responsive to the likelihood being less than a threshold.

8. The method of claim 7, further comprising:

continuing the pressure rise portion of the engine-off natural vacuum test responsive to the likelihood being greater than the threshold.

9. A method, comprising:

adjusting an evaporative emissions leak test parameter based on a time-weighted driving aggressiveness index; and

indicating degradation based on the adjusted parameter.

10. The method of claim 9, wherein the time-weighted driving aggressiveness index is based on an engine heat rejection inference during a vehicle run time duration.

11. The method of claim 10, wherein the vehicle run time duration is a total vehicle run time between a most recent vehicle-off event and a previous vehicle-on event.

12. The method of claim 11, wherein the engine heat rejection inference is based on an engine load between the most recent vehicle-off event and the previous vehicle-on event.

13. The method of claim 12, wherein the time-weighted driving aggressiveness index weights time periods closer to the most recent vehicle-off event more than time periods closer to the previous vehicle-on event.

14. The method of claim 9, wherein the evaporative emissions leak test is an engine-off natural vacuum test.

15. The method of claim 14, wherein the evaporative emissions leak test parameter is a pressure rise threshold for the engine-off natural vacuum test.

16. The method of claim 14, wherein the evaporative emissions leak test parameter is a vacuum threshold for the engine-off natural vacuum test.

17. The method of claim 9, further comprising:

initiating the evaporative emissions leak test only when time-weighted driving aggressiveness index is greater than a threshold.

18. The method of claim 9, wherein the evaporative emissions leak test parameter is further adjusted based on a resistance of a heating element of a heated exhaust gas oxygen sensor.

19. A vehicle system, comprising:

a fuel system isolatable from atmosphere via one or more valves; and

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

adjust one or more thresholds for an engine-off natural vacuum test based on a time-weighted driving aggressiveness index;

following a vehicle-off event, isolate the fuel system from atmosphere; and

indicate degradation of the fuel system based on the one or more adjusted thresholds.

20. The vehicle system of claim 19, where the controller is configured with instructions stored in non-transitory memory, that when executed, cause the controller to:

responsive to an initial rate of change of fuel tank pressure being less than a threshold,

terminate a pressure rise portion of the engine-off natural vacuum test; and

initiate a vacuum portion of the engine-off natural vacuum test responsive to terminating the pressure rise portion of the engine-off natural vacuum test.