Fuel vapor leak test system and method comprising successive series of pulse bursts and pressure measurements between bursts

• US 20030192365A1
• Filed: 04/15/2002
• Published: 10/16/2003
• Est. Priority Date: 04/15/2002
• Status: Active Grant

• Current Assignee: Siemens VDO Automotive, Inc. (Continental AG)
• Original Assignee: Siemens VDO Automotive, Inc. (Continental AG)
• Inventors: Perry, Paul D., Rasokas, Raymond
• Granted Patent: US 6,951,126 B2
• Time in Patent Office: Days
• US Class Current: 73/49.7
• CPC Class Codes: F02M 2025/0845 Electromagnetic valves
• CPC Class Codes: F02M 25/0809 Judging failure of purge control system
• CPC Class Codes: F02M 25/0818 having means for pressurising the evaporative emission space
• 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

Abstract

A leak test system and method for a motor vehicle fuel system. A pump forces air under pressure into vapor containment space. The pump operates in accordance with steps established by a processor. The pump creates superatmospheric pressure in the space during an initial charging phase step, and after completion of that step, the pump performs a measurement phase step that forces pulses of air into the space in a succession of pulse bursts. Each burst contains a succession of individual pulses, preferably in equal numbers, and each successive burst is delayed from an immediately prior burst by a time interval substantially longer than the time intervals between individual pulses in each burst, preferably by constant time intervals. The processor processes data corresponding to a measurement of pressure in the space after the occurrence of at least one of such bursts and as a result indicates leakage from the space.

Claims

1. A leak test system for a motor vehicle fuel system that holds volatile liquid fuel for operating the vehicle, the leak test system comprising:

a processor for establishing steps of a leak test;

a pump for forcing air under pressure into vapor containment space of the fuel system during a leak test;

a pump operator that operates the pump in accordance with steps established by the processor to cause the pump to create a superatmospheric pressure in the space during an initial step of the leak test, and that, after completion of the initial step, causes the pump to perform a further step that comprises forcing pulses of air into the space in a succession of pulse bursts, wherein each burst comprises a succession of individual pulses of air, and each successive burst is delayed from an immediately prior burst by a time interval substantially longer than the time intervals between individual pulses in each burst; and

wherein the processor processes data corresponding to a measurement of pressure in the space after the occurrence of at least one of such bursts and as a result of that processing indicates leakage from the space.

2. A leak test system as set forth in claim 1 wherein during the initial step of the leak test, the processor performs a pressure progress test to ascertain if pressure is increasing sufficiently fast in the space to allow a valid leak test to be completed within an amount of time allotted for the leak test.

3. A leak test system as set forth in claim 2 wherein the pressure progress test comprises the processor processing data corresponding to a measurement of pressure in the space and data defining an intermediate pressure representing a measure of progress in creating suitable superatmospheric pressure in the space that will enable the leak test to be performed within the amount of time allotted for the leak test, and if the latter processing discloses that pressure in the space is not less than the intermediate pressure, the processor allows the leak test to continue.

4. A leak test system as set forth in claim 3 wherein the pressure progress test also includes the processor processing data representing elapse of time since the beginning of the initial step of the leak test and data representing an intermediate time limit, and if both

a) the processing of data corresponding to a measurement of pressure in the space and data defining the intermediate pressure discloses that pressure in the space is not less than the intermediate pressure, and

b) the processing of data representing elapse of time since the beginning of the initial step of the leak test and data representing an intermediate time limit discloses that elapse of time since the beginning of the initial step of the leak test is less than the intermediate time limit,

the processor allows the leak test to continue.

5. A leak test system as set forth in claim 3 wherein, if the processor allows the leak test to continue after having completed the pressure progress test, the processor processes data corresponding to a measurement of pressure in the space and data defining the suitable superatmospheric pressure, and if the processing of the data corresponding to a measurement of pressure in the space and the data defining the suitable superatmospheric pressure discloses that pressure in the space is not less than the suitable superatmospheric pressure, the processor initiates the further step of the leak test.

6. A leak test system as set forth in claim 5 wherein, if the processor allows the leak test to continue after having completed the pressure progress test, the processor processes data corresponding to a measurement of pressure in the space and data defining the suitable superatmospheric pressure for performing the leak test and also processes data representing elapse of time since the beginning of the initial step of the leak test and data representing a maximum allowable leak test time, and if both

a) the processing of the data corresponding to a measurement of pressure in the space and the data defining the suitable superatmospheric pressure for performing the leak test discloses that pressure in the space is not less than the suitable superatmospheric pressure, and

b) the processing of data representing elapse of time since the beginning of the initial step of the leak test and data representing the maximum allowable leak test time discloses that elapse of time since the beginning of the initial step of the leak test has not exceeded maximum allowable leak test time,

the processor initiates the further step of the leak test.

7. A leak test system as set forth in claim 6 wherein the processing of data representing elapse of time since the beginning of the initial step of the leak test and data representing the maximum allowable leak test time comprises the processor processing data representing elapse of time since the beginning of the initial step of the leak test and data representing a maximum time allowed for the pump to increase the pressure in the space from the pressure present at the beginning of the initial step of the leak test to the suitable superatmospheric pressure in the presence of a leak smaller than a gross leak.

8. A leak test system as set forth in claim 5 wherein, if the processor allows the leak test to continue after having completed the pressure progress test, the processor processes data corresponding to a measurement of pressure in the space and data defining the suitable superatmospheric pressure for performing the leak test and also processes data representing elapse of time since the pressure progress test and data representing a maximum allowable time for the pressure to increase from the intermediate pressure to the suitable superatmospheric pressure, and if both

a) the processing of the data corresponding to a measurement of pressure in the space and the data defining the suitable superatmospheric pressure for performing the leak test discloses that pressure in the space is not less than the suitable superatmospheric pressure, and

b) the processing of data representing elapse of time since the pressure progress test and data representing the maximum allowable time for the pressure to increase from the intermediate pressure to the suitable superatmospheric pressure discloses that elapse of time since the pressure progress test time has not exceeded the maximum allowable time for the pressure to increase from the intermediate pressure to the suitable superatmospheric pressure,

the processor initiates the further step of the leak test.

9. A leak test system as set forth in claim 8 wherein the processing of data representing elapse of time since the conclusion of the pressure progress test and data representing the maximum allowable time for the pressure to increase from the intermediate pressure to the suitable superatmospheric pressure comprises the processor processing data representing elapse of time since the conclusion of the pressure progress test and data representing a maximum time allowed for the pump to increase the pressure in the space from the intermediate pressure to the suitable superatmospheric pressure in the presence of a leak smaller than a gross leak.

10. A leak test system as set forth in claim 5 wherein, if the processor allows the leak test to continue after having completed the pressure progress test, the processor processes data corresponding to a measurement of pressure in the space and data defining the suitable superatmospheric pressure for performing the leak test, processes data representing elapse of time since the beginning of the initial step of the leak test and data representing a maximum allowable leak test time in the presence of a leak smaller than a gross leak, and processes data representing elapse of time since the pressure progress test and data representing a maximum allowable time for the pressure to increase from the intermediate pressure to the suitable superatmospheric pressure in the presence of a leak smaller than a gross leak, and if

a) the processing of the data corresponding to a measurement of pressure in the space and the data defining the suitable superatmospheric pressure for performing the leak test discloses that pressure in the space is not less than the suitable superatmospheric pressure,

b) the processing of data representing elapse of time since the beginning of the initial step of the leak test and data representing the maximum allowable leak test time in the presence of a leak smaller than a gross leak discloses that elapse of time since the beginning of the initial step of the leak test has not exceeded maximum allowable leak test time in the presence of a leak smaller than a gross leak, and

c) the processing of data representing elapse of time since the pressure progress test and data representing the maximum allowable time for the pressure to increase from the intermediate pressure to the suitable superatmospheric pressure in the presence of a leak smaller than a gross leak discloses that elapse of time since the pressure progress test time has not exceeded the maximum allowable time for the pressure to increase from the intermediate pressure to the suitable superatmospheric pressure in the presence of a leak smaller than a gross leak,

the processor initiates the further step of the leak test.

11. A leak test system as set forth in claim 1 wherein the pump comprises a diaphragm pump that is repeatedly stroked to force air into the space.

12. A leak test system as set forth in claim 11 wherein during the further step of the leak test, each stroke of the diaphragm pump creates a corresponding pulse of air that is forced into the space.

13. A leak test system as set forth in claim 1 wherein during the further step of the leak test, the processor causes the pump to force pulses of air into the space in a succession of pulse bursts, wherein each burst comprises a succession of individual pulses of air in substantially equal numbers of pulses, and each successive burst is delayed from an immediately prior burst by substantially the same amount of time.

14. A leak test system as set forth in claim 13 wherein the number of pulses in each burst and the amount of time by which each successive burst is delayed from an immediately prior burst define a boundary value that distinguishes between a fuel system that has excessive leakage and one that does not, and wherein the processor processes the data corresponding to a measurement of pressure in the space after the occurrence of at least one of such bursts and the boundary value for indicating leakage from the space by distinguishing between a fuel system that has excessive leakage and one that does not.

15. A leak test system as set forth in claim 1 wherein the processor processes data corresponding to measurements of pressure in the space after each of selected ones of such bursts and as a result of the latter processing indicates leakage from the space.

16. A leak test method for a motor vehicle fuel system that holds volatile liquid fuel for operating the vehicle, the method comprising:

forcing air under pressure into vapor containment space of the fuel system during a leak test in accordance with steps of the method;

wherein during an initial step of the method, the forcing of air into the space creates in the space a superatmospheric pressure suitable for performing the leak test; and

after completion of the initial step, operating a pump to perform a further step of the method that comprises forcing pulses of air into the space in a succession of pulse bursts, wherein each burst comprises a succession of individual pulses of air, and each successive burst is delayed from an immediately prior burst by a time interval substantially longer than the time intervals between individual pulses in each burst; and

processing data corresponding to a measurement of pressure in the space after the occurrence of at least one of such bursts and indicating leakage from the space as a result of that processing.

17. A method as set forth in claim 16 including the step of performing a pressure progress test during the initial step of the leak test to ascertain if pressure is increasing sufficiently fast in the space to allow a valid leak test to be completed within an amount of time allotted for the leak test.

18. A method as set forth in claim 17 wherein the step of performing a pressure progress test comprises processing data corresponding to a measurement of pressure in the space and data defining an intermediate pressure representing a measure of progress in creating suitable superatmospheric pressure in the space that will enable the leak test to be performed within the amount of time allotted for the leak test, and if the latter processing discloses that pressure in the space is not less than the intermediate pressure, allowing the leak test to continue.

19. A method as set forth in claim 18 wherein the step of performing a pressure progress test also includes processing data representing elapse of time since the beginning of the initial step of the leak test and data representing an intermediate time limit, and if both

a) the processing of data corresponding to a measurement of pressure in the space and data defining the intermediate pressure discloses that pressure in the space is not less than the intermediate pressure, and

b) the processing of data representing elapse of time since the beginning of the initial step of the leak test and data representing an intermediate time limit discloses that elapse of time since the beginning of the initial step of the leak test is less than the intermediate time limit,

allowing the leak test to continue.

20. A method as set forth in claim 18 wherein, if the leak test is allowed to continue after completion of the pressure progress test, performing the further step of processing data corresponding to a measurement of pressure in the space and data defining the suitable superatmospheric pressure, and if the processing of the data corresponding to a measurement of pressure in the space and the data defining the suitable superatmospheric pressure discloses that pressure in the space is not less than the suitable superatmospheric pressure, initiating the further step of the leak test.

21. A method as set forth in claim 20 wherein, if the leak test is allowed to continue after completion of the pressure progress test, performing the steps of processing data corresponding to a measurement of pressure in the space and data defining the suitable superatmospheric pressure for performing the leak test and also of processing data representing elapse of time since the beginning of the initial step of the leak test and data representing a maximum allowable leak test time, and if both

a) the processing of the data corresponding to a measurement of pressure in the space and the data defining the suitable superatmospheric pressure for performing the leak test discloses that pressure in the space is not less than the suitable superatmospheric pressure, and

b) the processing of data representing elapse of time since the beginning of the initial step of the leak test and data representing the maximum allowable leak test time discloses that elapse of time since the beginning of the initial step of the leak test has not exceeded maximum allowable leak test time,

initiating the further step of the leak test.

22. A method as set forth in claim 21 wherein the processing of data representing elapse of time since the beginning of the initial step of the leak test and data representing the maximum allowable leak test time comprises processing data representing elapse of time since the beginning of the initial step of the leak test and data representing a maximum time allowed for the pump to increase the pressure in the space from the pressure present at the beginning of the initial step of the leak test to the suitable superatmospheric pressure in the presence of a leak smaller than a gross leak.

23. A method as set forth in claim 20 wherein, if the leak test is allowed to continue after the pressure progress test has been completed, performing the steps of processing data corresponding to a measurement of pressure in the space and data defining the suitable superatmospheric pressure for performing the leak test and also of processing data representing elapse of time since the pressure progress test and data representing a maximum allowable time for the pressure to increase from the intermediate pressure to the suitable superatmospheric pressure, and if both

a) the processing of the data corresponding to a measurement of pressure in the space and the data defining the suitable superatmospheric pressure for performing the leak test discloses that pressure in the space is not less than the suitable superatmospheric pressure, and

b) the processing of data representing elapse of time since the pressure progress test and data representing the maximum allowable time for the pressure to increase from the intermediate pressure to the suitable superatmospheric pressure discloses that elapse of time since the pressure progress test time has not exceeded the maximum allowable time for the pressure to increase from the intermediate pressure to the suitable superatmospheric pressure,

the processor initiates the further step of the leak test.

24. A method as set forth in claim 23 wherein the processing of data representing elapse of time since the conclusion of the pressure progress test and data representing the maximum allowable time for the pressure to increase from the intermediate pressure to the suitable superatmospheric pressure comprises processing data representing elapse of time since the conclusion of the pressure progress test and data representing a maximum time allowed for the pump to increase the pressure in the space from the intermediate pressure to the suitable superatmospheric pressure in the presence of a leak smaller than a gross leak.

25. A method as set forth in claim 20 wherein, if the leak test is allowed to continue after completion of the pressure progress test, performing the steps of processing data corresponding to a measurement of pressure in the space and data defining the suitable superatmospheric pressure for performing the leak test, of processing data representing elapse of time since the beginning of the initial step of the leak test and data representing a maximum allowable leak test time in the presence of a leak smaller than a gross leak, and of processing data representing elapse of time since the pressure progress test and data representing a maximum allowable time for the pressure to increase from the intermediate pressure to the suitable superatmospheric pressure in the presence of a leak smaller than a gross leak, and if

a) the processing of the data corresponding to a measurement of pressure in the space and the data defining the suitable superatmospheric pressure for performing the leak test discloses that pressure in the space is not less than the suitable superatmospheric pressure,

b) the processing of data representing elapse of time since the beginning of the initial step of the leak test and data representing the maximum allowable leak test time in the presence of a leak smaller than a gross leak discloses that elapse of time since the beginning of the initial step of the leak test has not exceeded maximum allowable leak test time in the presence of a leak smaller than a gross leak, and

c) the processing of data representing elapse of time since the pressure progress test and data representing the maximum allowable time for the pressure to increase from the intermediate pressure to the suitable superatmospheric pressure in the presence of a leak smaller than a gross leak discloses that elapse of time since the pressure progress test time has not exceeded the maximum allowable time for the pressure to increase from the intermediate pressure to the suitable superatmospheric pressure in the presence of a leak smaller than a gross leak,

initiating the further step of the leak test.

26. A method as set forth in claim 16 wherein the step of operating a pump to perform a further step of the method that comprises forcing pulses of air into the space in a succession of pulse bursts comprises repeatedly stroking a diaphragm pump.

27. A method as set forth in claim 26 wherein during the further step of the leak test, the step of repeatedly stroking a diaphragm pump comprises forcing a pulse of air into the space as a result of each stroke of the diaphragm pump.

28. A method as set forth in claim 16 wherein during the further step of the leak test, the step of operating the pump comprises operating the pump to force pulses of air into the space in a succession of pulse bursts, wherein each burst comprises a succession of individual pulses of air in substantially equal numbers of pulses, and each successive burst is delayed from an immediately prior burst by substantially the same amount of time.

29. A method as set forth in claim 28 wherein the number of pulses in each burst and the amount of time by which each successive burst is delayed from an immediately prior burst define a boundary value that distinguishes between a fuel system that has excessive leakage and one that does not, and wherein the step of processing data corresponding to a measurement of pressure in the space after the occurrence of at least one of such bursts and indicating leakage from the space as a result of that processing comprises processing the data corresponding to a measurement of pressure in the space after the occurrence of at least one of such bursts and the boundary value for indicating leakage from the space by distinguishing between a fuel system that has excessive leakage and one that does not.

30. A method as set forth in claim 16 wherein the processing comprises processing data corresponding to measurements of pressure in the space after each of selected ones of such bursts and as a result of the latter processing indicating leakage from the space.

31. A method as set forth in claim 16 wherein the step of forcing air into the space during the initial step of the method to create superatmospheric pressure suitable for performing the leak test comprises operating the pump to create the superatmospheric pressure.