Evaporative emission control for very small leak detection

• US 6,314,797 B1
• Filed: 08/30/1999
• Issued: 11/13/2001
• Est. Priority Date: 08/30/1999
• Status: Expired due to Term

• Current Assignee: FCA US LLC (Stellantis NV)
• Original Assignee: Daimler Chrysler Corporation (Mercedes-Benz Group AG)
• Inventors: Booms, Chris J., Blomquist, William B., Dawson, Gary D.
• Primary Examiner(s): LARKIN, DANIEL SEAN
• Application Number:
  US09/385,206
• Time in Patent Office: 806 Days
• Field of Search: 73/492, 73/497, 123/520
• US Class Current: 73/49.2
• CPC Class Codes: F02D 41/042 for stopping the engine
• CPC Class Codes: F02M 25/0809 Judging failure of purge control system

Abstract

A method is provided for detecting a very small leak in an evaporative emission control system of an automotive vehicle. The method includes sealing the evaporative emission control system at a key-off event and monitoring a vacuum switch coupled to the evaporative emission control system for a closing event due to a natural vacuum created in the evaporative emission control system as it cools. If the closing event is not detected, the method determines if a leak detection timer has exceeded a predetermined threshold value. If the timer has exceeded the predetermined threshold value, the method sets a fault code indicating that the very small leak has been detected. Preferably, the leak detection timer includes a first time value corresponding to an amount of time the automotive vehicle has been operating since a previous small leak detection test was conducted and a second time value corresponding to an amount of time the automotive vehicle has been inoperative since a previous small leak detection test was conducted. The first time value includes a series of individual trip times of the automotive vehicle while the second time value includes a series of individual inoperative session times of the automotive vehicle.

Claims

1. A method of detecting a very small leak in an evaporative emission control system of an automotive vehicle comprising:

sealing said evaporative emission control system at a key-off event;

monitoring a vacuum switch coupled to said evaporative emission control system for a closing event due to a vacuum created in said evaporative emission control system;

determining if a leak detection timer has exceeded a predetermined threshold value if said closing event is not detected; and

setting a fault code indicating that said very small leak has been detected if said timer has exceeded said predetermined threshold value;

wherein said leak detection timer further comprises a first time value corresponding to an amount of time said automotive vehicle has been operating since a previous small leak detection test was conducted.

2. The method of claim 1 wherein said first time value further comprises a series of individual trip times of said automotive vehicle.

3. The method of claim 1 wherein said leak detection timer further comprises a second time value corresponding to an amount of time said automotive vehicle has been inoperative since a previous small leak detection test was conducted.

4. The method of claim 3 wherein said second time value further comprises a series of individual inoperative session times of said automotive vehicle.

5. The method of claim 1 further comprising determining that a set of operating conditions are met prior to said step of determining if said leak detection timer has exceeded said predetermined threshold value.

6. The method of claim 5 wherein said set of operating conditions further comprise that an ambient temperature is between a minimum and maximum ambient temperature.

7. The method of claim 5 wherein wherein said set of operating conditions further comprise that a fuel level is between a minimum and maximum fuel level.

8. The method of claim 5 wherein wherein said set of operating conditions further comprise that a battery voltage is between a minimum and maximum battery voltage.

9. The method of claim 5 wherein wherein said set of operating conditions further comprise that an altitude is less than a maximum altitude.

10. The method of claim 1 further comprising determining that a minimum operating time has elapsed prior to said step of determining if said leak detection timer has exceeded said predetermined threshold value.

12. The method of claim 1 wherein said very small leak further comprises a hole having a diameter of approximately 0.020 inches or greater.

18. The method of claim 1 wherein said step of sealing said evaporative emission control system further comprises shutting a valve disposed along a first conduit extending between a canister of said evaporative emission control system and atmosphere.

19. The method of claim 18 wherein said step of sealing said evaporative emission control system further comprises shutting a valve disposed along a second conduit extending between the canister of said evaporative emission control system and a manifold of the automotive vehicle.

11. A method of detecting a very small leak in an evaporative emission control system of an automotive vehicle comprising:

sealing said evaporative emission control system at a key-off event;

monitoring a vacuum switch coupled to said evaporative emission control system for a closing event due to a vacuum created in said evaporative emission control system;

determining if a leak detection timer has exceeded a predetermined threshold value if said closing event is not detected;

setting a fault code indicating that said very small leak has been detected if said timer has exceeded said predetermined threshold value; and

determining that a minimum inoperative time has elapsed prior to said step of determining if said leak detection timer has exceeded said predetermined threshold value.

13. A method of detecting a very small leak in an evaporative emission control system of an automotive vehicle comprising:

sealing said evaporative emission control system at a key-off event;

monitoring a vacuum switch coupled to said evaporative emission control system for a closing event due to a vacuum created in said evaporative emission control system;

determining if a leak detection timer has exceeded a predetermined threshold value if said closing event is not detected; and

setting a fault code indicating that said very small leak has been detected if said timer has exceeded said predetermined threshold value;

wherein said predetermined threshold value further comprises about one hundred sixty-eight hours.

14. A method of detecting a very small leak in an evaporative emission control system of an automotive vehicle comprising:

sealing said evaporative emission control system at a key-off event;

monitoring a vacuum switch coupled to said evaporative emission control system for a closing event due to a vacuum created in said evaporative emission control system;

determining if a leak detection timer has exceeded a predetermined threshold value if said closing event is not detected;

setting a fault code indicating that said very small leak has been detected if said timer has exceeded said predetermined threshold value; and

opening a pressure relief valve coupled to said evaporative emission control system if a pressure within said evaporative emission control system exceeds a given value.

15. The method of claim 14 wherein said given value is approximately equal to one inch of H₂O.

16. A method of detecting a very small leak in an evaporative emission control system of an automotive vehicle comprising:

sealing said evaporative emission control system at a key-off event;

monitoring a vacuum switch coupled to said evaporative emission control system for a closing event due to a vacuum created in said evaporative emission control system;

determining if a leak detection timer has exceeded a predetermined threshold value if said closing event is not detected;

setting a fault code indicating that said very small leak has been detected if said timer has exceeded said predetermined threshold value; and

opening a vacuum relief valve coupled to said evaporative emission control system if a pressure within said evaporative emission control system drops below a given value.

17. The method of claim 16 wherein said given value is approximately equal to three inches of H₂O.