Positive pressure canister purge system integrity confirmation

• US 5,297,529 A
• Filed: 01/27/1993
• Issued: 03/29/1994
• Est. Priority Date: 01/27/1993
• Status: Expired due to Fees

• Current Assignee: Siemens Automotive Ltd (Siemens AG)
• Original Assignee: Siemens Automotive Ltd (Siemens AG)
• Inventors: Cook, John E., Busato, Murray F.
• Primary Examiner(s): Cross, E. Rollins
• Assistant Examiner(s): Moulis, Thomas N.
• Application Number:
  US08/009,623
• Time in Patent Office: 426 Days
• Field of Search: 123/516, 123/518, 123/519, 123/520, 123/521, 123/198 D, 73/118.1
• US Class Current: 123/520
• CPC Class Codes: F02M 2025/0845 Electromagnetic valves
• CPC Class Codes: F02M 25/0818 having means for pressurising the evaporative emission space

Abstract

The tank/canister volume'"'"'s integrity against unacceptable leakage is either confirmed or denied by a diagnostic test performed by an on-board diagnostic system which includes an electrically operated air pump and tank-mounted analog pressure transducer. At the beginning of a test, the engine management computer closes the canister purge solenoid valve and operates the pump to begin pressurization of the tank/canister volume. The pumped air is introduced via the canister'"'"'s atmospheric vent port so that the pressurizing air is entrained with fuel vapors previously collected in, but not yet purged from, the canister. Failure to build to a predetermined pressure within a predetermined time indicates a gross leak. Upon attainment of the predetermined pressure, the pump is shut off. If the pressure drops by more than a certain amount during the test, integrity is denied. If not, integrity is confirmed.

Claims

1. A canister purge system comprising a collection canister for collecting volatile fuel vapors from a fuel tank, and means for selectively purging collected fuel vapors from said canister to an internal combustion engine'"'"'s intake manifold for entrainment with a combustible mixture that passes from the intake manifold into combustion chamber space of the engine for combustion therein, said means including a purge flow path between said canister and intake manifold, said canister having tank port means for communicating said canister with said fuel tank and other port means for communicating said canister with other than said fuel tank, characterized by an associated diagnostic system for detecting leakage from a portion of the canister purge system, which portion includes said canister and tank, said diagnostic system comprising means for positively pressurizing said portion to a predetermined positive pressure, detecting means for detecting loss of said predetermined positive pressure indicative of leakage from said portion, and signaling means for giving a signal indicative of such loss, and further characterized in that said means for positively pressurizing said portion of said canister purge system comprises means for positively pressurizing said portion through said other port means by pumping atmospheric air into said portion through a vapor collection medium within said canister so that pressurizing air entering said portion is entrained with some of the fuel vapors previously collected in said canister.

2. A canister purge system as set forth in claim 1 characterized further in that said means for positively pressurizing said portion to a predetermined positive pressure comprises an electrically operated pump.

3. A canister purge system as set forth in claim 1 characterized further in that said detecting means comprises an analog pressure transducer.

4. In an automotive vehicle comprising an internal combustion engine for powering the vehicle, an engine management computer for controlling certain functions associated with the operation of said engine, said engine comprising an intake manifold within which vacuum is created during operation of the engine, said vehicle comprising a fuel tank for containing a supply of a volatile liquid fuel for the engine, and an evaporative emission control system comprising a collection canister for collecting volatile fuel vapors from the fuel tank, a vent valve that is between atmosphere and an atmospheric vent port of said canister, and means for selectively purging collected fuel vapors from said canister to an intake manifold of said engine for entrainment with a combustible mixture that passes from the intake manifold into combustion chamber space of the engine for combustion therein, said means including a purge flow path comprising a canister purge solenoid valve that is between a purge port of said canister and said intake manifold and is under the control of said engine management computer, the improvement characterized in that said vent valve is solenoid-operated and under the control of said engine management computer, and further characterized by an associated diagnostic system for detecting unacceptable leakage from a portion of the evaporative emission control system, which portion includes said canister and tank, said diagnostic system comprising an electrically operated pump for positively pressurizing said portion to a predetermined positive pressure by pressurizing said portion via said atmospheric vent port of said canister, a check valve for preventing loss of positive pressure from said portion of said canister purge system back through said pump, detecting means for detecting pressure in said portion, and means operatively relating said canister purge solenoid valve, said detecting means, said pump, said vent valve, and said computer in performing a diagnostic test for confirming the integrity of said portion against unacceptable leakage wherein both said vent valve and said canister purge solenoid valve are operated closed and said pump is operated to build positive pressure in said portion until pressure in said portion has been built to a predetermined positive pressure whereupon said pump ceases building positive pressure in said portion so that the positive pressure in said portion as trapped therein by said check valve upon said pump ceasing to build positive pressure in said portion is essentially equal to said predetermined positive pressure, and unacceptable leakage from said portion is indicated by pressure in said portion decreasing from said predetermined positive pressure by a predetermined amount within a predetermined time.

5. The improvement set forth in claim 4 further including correction factor means comprising means for storing correction factors based on at least one of fuel temperature, rate of fuel vapor generation in the tank, and tank fill level, and means for applying said correction factors to the measured decrease in pressure in said portion to correct for at least one of actual fuel temperature, actual rate of fuel vapor generation in the tank, and actual tank fill level.

6. In an automotive vehicle comprising an internal combustion engine for powering the vehicle, an engine management computer for controlling certain functions associated with the operation of said engine, said engine comprising an intake manifold within which vacuum is created during operation of the engine, said vehicle comprising a fuel tank for containing a supply of a volatile liquid fuel for the engine, and an evaporative emission control system comprising a collection canister for collecting volatile fuel vapors from the fuel tank, a vent valve that is between atmosphere and an atmospheric vent port of said canister, and means for selectively purging collected fuel vapors from said canister to an internal combustion engine'"'"'s intake manifold for entrainment with a combustible mixture that passes from the intake manifold into combustion chamber space of the engine for combustion therein, said means including a purge flow path comprising a canister purge solenoid valve that is between said canister and said intake manifold and that is under the control of said engine management computer, the improvement characterized in that said vent valve is solenoid-operated and under the control of said engine management computer, and further characterized by an associated diagnostic system for detecting unacceptable leakage from a portion of the evaporative emission control system, which portion includes said canister and tank, said diagnostic system comprising an electrically operated pump for positively pressurizing said portion to a predetermined positive pressure by pressurizing said portion via said atmospheric vent port of said canister, a check valve for preventing loss of positive pressure from said portion back through said pump, detecting means for detecting pressure in said portion, and means operatively relating said canister purge solenoid valve, said detection means, said pump, said vent valve, and said computer in performing a diagnostic test for confirming the integrity of said portion against unacceptable leakage wherein both said vent valve and said canister purge solenoid valve are operated closed and said pump is operated to build positive pressure in said portion, and unacceptable leakage in said portion is indicated if pressure in said portion is not built to a predetermined positive pressure within a predetermined amount of time.

7. A canister purge system comprising a collection canister for collecting volatile fuel vapors from a fuel tank, and means for selectively purging collected fuel vapors from said canister to an internal combustion engine'"'"'s intake manifold for entrainment with a combustible mixture that passes from the intake manifold into combustion chamber space of the engine for combustion therein, said means including a purge flow path from said canister to said intake manifold, characterized by an associated diagnostic system for confirming the absence of unacceptable leakage from a portion of the canister purge system, which portion includes said canister and tank, said diagnostic system comprising means for positively pressurizing said portion to a predetermined positive pressure by means of air drawn from atmosphere and introduced into said flow path via said canister such that the drawn air passes through a vapor collection medium within said canister before it reaches said purge flow path and said tank so that pressurizing air entering said purge flow path and tank is entrained with some of the fuel vapors previously collected by said canister, detecting means for detecting the absence of a predetermined amount of decrease in the positive pressure in said portion from said predetermined positive pressure within a predetermined amount of time, which predetermined amount of decrease with said predetermined amount of time is indicative of unacceptable leakage from said portion, and signaling means for giving a signal indicative of such absence.

8. A canister purge system as set forth in claim 7 characterized further in that said means for positively pressurizing said portion to a predetermined positive pressure comprises an electrically operated pump.

9. A canister purge system as set forth in claim 7 characterized further in that said detecting means comprises an analog pressure transducer.

10. A canister purge system as set forth in claim 7 further including correction factor means comprising means for storing correction factors based on at least one of fuel temperature, rate of fuel vapor generation in the tank, and tank fill level, and means for applying said correction factors to the measured decrease in pressure in said portion to correct for at least one of actual fuel temperature, actual rate of fuel vapor generation in the tank, and actual tank fill level.

11. In a canister purge system comprising a collection canister for collecting volatile fuel vapors from a fuel tank, and means for selectively purging collected fuel vapors from said canister to an internal combustion engine'"'"'s intake manifold for entrainment with a combustible mixture that passes from the intake manifold into combustion chamber space of the engine for combustion therein, said means including a purge flow path between said canister and intake manifold, a method for diagnosing unacceptable leakage from a portion of the canister purge system, which portion includes said canister and tank, said method comprising positively pressurizing said portion to a predetermined positive pressure by pumping atmospheric air into said portion such that before it enters said purge flow path and tank, it passes through a vapor collection medium within said canister so that pressurizing air entering said said purge flow path and tank is entrained with some of the fuel vapors previously collected by said canister, detecting a predetermined amount of decrease in the positive pressure in said portion from said predetermined positive pressure within a predetermined amount of time, which predetermined amount of decrease within said predetermined amount of time is indicative of unacceptable leakage from said portion, and giving a signal to indicate such unacceptable leakage.

12. A method as set forth in claim 11 further including applying correction factors obtained from stored correction factor data based on at least one of fuel temperature, rate of fuel vapor generation in the tank, and tank fill level to the measured decrease in pressure in said portion to correct for at least one of actual fuel temperature, actual rate of fuel vapor generation in the tank, and actual tank fill level.

13. In a canister purge system comprising a collection canister for collecting volatile fuel vapors from a fuel tank, and means for selectively purging collected fuel vapors from said canister to an internal combustion engine'"'"'s intake manifold for entrainment with a combustible mixture that passes from the intake manifold into combustion chamber space of the engine for combustion therein, said means including a purge flow path between said canister and intake manifold, characterized by a method for confirming the absence of unacceptable leakage from a portion of the canister purge system, which portion includes said canister and tank, said method comprising positively pressurizing said portion to a predetermined positive pressure by pumping atmospheric air into said portion via said canister such that before it enters said purge flow path and tank, it passes through a vapor collection medium within said canister so that pressurizing air entering said purge flow path and tank is entrained with some of the fuel vapors previously collected by said canister, detecting the absence of a predetermined amount of decrease in the positive pressure in said portion from said predetermined positive pressure within a predetermined amount of time, which predetermined amount of decrease within said predetermined amount of time is indicative of unacceptable leakage from said portion, and giving a signal indicative of such absence.