Method and system for aggressive cycling of leak detection pump to ascertain vapor leak size

• US 6,446,492 B2
• Filed: 06/08/2001
• Issued: 09/10/2002
• Est. Priority Date: 12/16/1999
• Status: Expired due to Fees

• Current Assignee: Siemens Canada Limited (Siemens AG)
• Original Assignee: Siemens Canada Limited (Siemens AG)
• Inventors: Weldon, Craig, Cook, John Edward, Rasokas, Ray
• Primary Examiner(s): Williams, Hezron
• Assistant Examiner(s): Politzer, J L
• Application Number:
  US09/877,841
• Publication Number:
  US 20010025523A1
• Time in Patent Office: 459 Days
• Field of Search: 73/407, 73/492, 73/405.R, 123/520, 702/51
• US Class Current: 73/49.2
• CPC Class Codes: F02M 25/0818 having means for pressurising the evaporative emission space

Abstract

A system and method for detecting leakage from a evaporative emission space of an automotive vehicle fuel system. A reciprocating pump is operated in a pressurizing mode to build pressure in the space toward a nominal test pressure. The pressurizing mode involves operating the pump in a repeating cycle wherein the pump operates alternately in an accelerated pumping mode and a natural frequency pumping mode. During the pressurizing mode, a characteristic of successive occurrences of the natural frequency pumping mode indicative of pressure in the space is measured. The number of times the cycle repeats is counted and compared to a predefined reference. When the cycle count exceeds the predefined reference, the test continues at a lower resolution for detecting leakage, and when the cycle count does not exceed the predefined reference and a measurement of the characteristic of successive occurrences of the natural frequency pumping mode indicative of pressure in the space exceeds a predetermined reference pressure, the test continues at a higher resolution for detecting leakage. The invention is useful when overall test time is limited.

Claims

1. A method for detecting leakage of vapor from an evaporative emission space of a fuel storage system of an automotive vehicle for storing volatile fuel consumed by the vehicle during operation, the method comprising:

pressurizing the evaporative emission space toward a nominal test pressure suitable for detecting leakage during a leak test;

during the pressurizing step, correlating pressure in the evaporative emission space with elapsed test time;

continuing the test at a relatively lower leak detection resolution when the correlating step indicates a relatively larger leak; and

continuing the test at a relatively higher leak detection resolution when the correlating step indicates a relatively smaller leak.

2. A method as set forth in claim 1 wherein the pressurizing step comprises operating a reciprocating pump to pressurize the evaporative emission space.

3. A method as set forth in claim 2 wherein the pump operates in a pressurizing mode to build pressure in the evaporative emission space toward a nominal test pressure, the pressurizing mode comprising operating the pump in a repeating cycle that comprises operating the pump alternately in an accelerated pumping mode and a natural frequency pumping mode;

the step of correlating pressure in the evaporative emission space with elapsed test time comprises measuring a characteristic of successive occurrences of the natural frequency pumping mode indicative of pressure in the evaporative emission space, counting the number of times the cycle repeats, and comparing the count to a predefined reference;

the step of continuing the test at a relatively lower leak detection resolution when the correlating step indicates a relatively larger leak comprises continuing the test at a lower resolution for detecting leakage when the cycle count exceeds the predefined reference; and

the step of continuing the test at a relatively higher leak detection resolution when the correlating step indicates a relatively smaller leak comprises continuing the test at a higher resolution for detecting leakage when the cycle count does not exceed the predefined reference and a measurement of the characteristic of successive occurrences of the natural frequency pumping mode indicative of pressure in the evaporative emission space exceeds a predetermined reference pressure.

4. A method as set forth in claim 3 including the steps of timing the duration of the test and when elapsed test time exceeds a predefined time limit, terminating the test.

5. A method as set forth in claim 4 including the step of indicating termination of the test as an aborted test if incipient stability of pressurization is not detected before elapsed test time exceeds the predefined time limit.

6. A method as set forth in claim 3 including the steps of timing duration of the test and detecting incipient stability of pressurization before elapsed test time exceeds a predefined time limit.

7. A method as set forth in claim 6 including the steps of predicting a final stabilized value of pressurization and of correlating that value with the resolution at which the test continued based on the cycle count.

8. A system for detecting leakage of vapor from an evaporative emission space of a fuel storage system of an automotive vehicle for storing volatile fuel consumed by the vehicle during operation, the system comprising:

pressurizing apparatus for pressurizing the evaporative emission space toward a nominal test pressure suitable for detecting leakage during a leak test;

and a processor that, during the pressurizing step, correlates pressure in the evaporative emission space with elapsed test time, that continues the test at a relatively lower leak detection resolution when the correlating step indicates a relatively larger leak, and that continues the test at a relatively higher leak detection resolution when the correlating step indicates a relatively smaller leak.

9. A system as set forth in claim 8 wherein the pressurizing apparatus comprises a reciprocating pump.

10. A system as set forth in claim 9 wherein the pump operates in a pressurizing mode to build pressure in the evaporative emission space toward a nominal test pressure, the pressurizing mode comprising operating the pump in a repeating cycle that comprises operating the pump alternately in an accelerated pumping mode and a natural frequency pumping mode;

the processor measures a characteristic of successive occurrences of the natural frequency pumping mode indicative of pressure in the evaporative emission space to thereby correlate pressure in the evaporative emission space with elapsed test time, counts the number of times the cycle repeats, and compares the count to a predefined reference;

the processor continues the test at a relatively lower leak detection resolution when the cycle count exceeds the predefined reference; and

the processor continues the test at a relatively higher leak detection resolution when the cycle count does not exceed the predefined reference and a measurement of the characteristic of successive occurrences of the natural frequency pumping mode indicative of pressure in the evaporative emission space exceeds a predetermined reference pressure.

11. A system as set forth in claim 10 wherein the processor times the duration of the test and when elapsed test time exceeds a predefined time limit, terminates the test.

12. A system as set forth in claim 11 wherein the processor indicates termination of the test as an aborted test if incipient stability of pressurization is not detected before elapsed test time exceeds the predefined time limit.

13. A system as set forth in claim 10 wherein the processor times duration of the test and detects incipient stability of pressurization before elapsed test time exceeds a predefined time limit.

14. A system as set forth in claim 13 wherein the processor predicts a final stabilized value of pressurization and correlates that value with the resolution at which the test continued based on the cycle count.