Leak detection system and method having self-compensation for changes in pressurizing pump efficiency

• US 6,622,545 B2
• Filed: 06/29/2001
• Issued: 09/23/2003
• Est. Priority Date: 06/29/2001
• Status: Expired due to Term

• Current Assignee: Siemens Automotive Inc (Continental AG)
• Original Assignee: Siemens VDO Automotive, Inc. (Continental AG)
• Inventors: Weldon, Craig Andrew, Rasokas, Raymond
• Primary Examiner(s): Williams, Hezron
• Assistant Examiner(s): WIGGINS, JOHN DAVID
• Application Number:
  US09/896,247
• Publication Number:
  US 20030000290A1
• Time in Patent Office: 816 Days
• Field of Search: 73/497, 73/40, 731/181, 73/11.6, 123/520
• US Class Current: 73/49.7
• CPC Class Codes: F02M 25/0818 having means for pressurising the evaporative emission space

Abstract

A leak detection system for a fuel system of an automotive vehicle has a diaphragm pump that is repeatedly stroked to pressurize vapor containment space of the fuel system during a leak detection test. A restriction is disposed between the pump and the space being pressurized to cause a real time pressure trace of pressure between the pump and the restriction to comprise a succession of pulses having peaks and valleys. Data from the first pump burst of the trace is used to adjust the number of times the pump is stroked during subsequent bursts to maintain substantially constant mass airflow into the space during each burst, thereby compensating for change in pump efficiency.

Claims

1. In a leak detection system for a fuel system of an automotive vehicle that contains volatile fuel for operating the vehicle, a leak detection module comprising:

an enclosure containing a diaphragm pump that is repeatedly stroked to force air through an outlet of the enclosure into a pressurized vapor containment space of the fuel system during a leak detection test;

a restriction that is disposed within the enclosure between the pump and the outlet to define within the enclosure a pressurized chamber where a real time pressure trace of pressure, as the pump is repeatedly stroked, comprises a succession of pulses having peaks and valleys; and

a pressure sensor that is ported to the chamber to provide such a pressure trace.

2. A leak detection system for a fuel system of an automotive vehicle that contains volatile fuel for operating the vehicle, the leak detection system comprising:

a diaphragm pump that is repeatedly stroked to pressurize a vapor containment space of the fuel system during a leak detection test;

a restriction that is disposed between the pump and the space being pressurized to cause a real time pressure trace of pressure between the pump and the restriction to comprise a succession of pulses having peaks and valleys; and

a processor for determining the difference between the peaks and valleys and for adjusting the number of times that the pump is subsequently stroked to maintain a substantially constant mass airflow into the space as efficiency of the pump changes.

3. A leak detection system for a fuel system of an automotive vehicle that contains volatile fuel for operating the vehicle, the leak detection system comprising:

a diaphragm pump that is repeatedly stroked to pressurize vapor containment space of the fuel system during a leak detection test;

a restriction that is disposed between the pump and the space being pressurized to cause a real time pressure trace of pressure between the pump and the restriction to comprise a succession of pulses having peaks and valleys; and

a processor for determining residual pressure when pump stroking ceases and for adjusting the number of times that the pump is subsequently stroked to maintain a substantially constant mass airflow into the space as efficiency of the pump changes.

4. In a leak detection system for a fuel system of an automotive vehicle that contains volatile fuel for operating the vehicle, a leak detection method comprising:

repeatedly stroking a diaphragm pump to pressurize a vapor containment space of the fuel system during a pressurizing phase of a leak detection test;

disposing a restriction between the pump and the space being pressurized to create a chamber where, as the pump is repeatedly stroked, causes a real time pressure trace of pressure to comprise a succession of pulses having peaks and valleys; and

sensing pressure in the chamber as the pump is stroked and processing data, including the sensed pressure, to develop data related to pump operating efficiency.

8. A leak detection method as set forth in claim 4 including:

changing the number of times that the pump is stroked during the pressurizing phase when the processing of data discloses a change in pump operating efficiency.

5. In a leak detection system for a fuel system of an automotive vehicle that contains volatile fuel for operating the vehicle, a leak detection method comprising:

repeatedly stroking a diaphragm pump to pressurize a vapor containment space of the fuel system during a leak detection test; and

disposing a restriction between the pump and the space being pressurized to cause a real time pressure trace of pressure between the pump and the restriction to comprise a succession of pulses having peaks and valleys; and

determining the difference between the peaks and valleys and adjusting the number of times that the pump is subsequently stroked to maintain a substantially constant mass airflow into the space as efficiency of the pump changes.

6. In a leak detection system for a fuel system of an automotive vehicle that contains volatile fuel for operating the vehicle, a leak detection method comprising:

repeatedly stroking a diaphragm pump to pressurize a vapor containment space of the fuel system during a leak detection test; and

disposing a restriction between the pump and the space being pressurized to cause a real time pressure trace of pressure between the pump and the restriction to comprise a succession of pulses having peaks and valleys; and

determining residual pressure when pump stroking ceases and adjusting the number of times that the pump is subsequently stroked to maintain a substantially consultant mass airflow into the space as efficiency of the pump changes.

7. A method for self-compensating a volumetric pump for decreasing volumetric efficiency so as to maintain a desired mass gas flow into a closed test space being tested for leakage, the method comprising:

operating the pump to pressurize the space during a leak detection test;

disposing a restriction between the pump and the space being pressurized to cause a real time pressure trace of pressure between the pump and the restriction to comprise a succession of pulses having peaks and valleys; and

utilizing data from the pressure trace to adjust pump operation to cause the pump to maintain the desired mass gas flow as pump efficiency changes.