Positive pressure canister purge system integrity confirmation

• US 5,146,902 A
• Filed: 12/02/1991
• Issued: 09/15/1992
• Est. Priority Date: 12/02/1991
• Status: Expired due to Term

• Current Assignee: Continental Automotive GmbH (Continental AG)
• Original Assignee: Continental Automotive GmbH (Continental AG)
• Inventors: Cook, John E., Busato, Murray F.
• Primary Examiner(s): Cross, E. Rollins
• Assistant Examiner(s): Moulis, Thomas N.
• Application Number:
  US07/801,322
• Time in Patent Office: 288 Days
• Field of Search: 123/479, 123/198 D, 123/516, 123/518, 123/519, 123/520, 123/521, 73/117.3, 73/118.1, 73/40 R, 73/40.1, 73/40.5, 73/40.7
• US Class Current: 123/518
• 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 a pressure switch. 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. Failure to build to a predetermined pressure indicates a gross leak. Upon attainment of the predetermined pressure, the pump is shut off by the operation of the pressure switch from one state to another. The pressure switch has hysteresis so that if the pressure falls below the predetermined pressure by a certain amount during the predetermined duration of the test, the pressure switch returns to its one state thereby giving a signal denying the integrity. Integrity is confirmed by the pressure switch remaining in its another state during the test.

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 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 an associated diagnostic system that detects unacceptable leakage from a portion of the canister purge system, which portion includes said canister and tank, and that comprises means for positively pressurizing said portion to a predetermined positive pressure, detecting means for detecting a certain decrease in the positive pressure, in said portion from said predetermined positive pressure indicative of unacceptable leakage from said portion, and signaling means for giving a signal indicative of such decrease.

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 characterized further in that said detecting means and said signaling means collectively comprise a pressure switch having a set of electrical contacts.

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 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, 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 intake manifold and that is under the control of said engine management computer, the improvement characterized by an associated diagnostic system that detects unacceptable leakage from a portion of the evaporative emission control system which portion includes said canister and tank and that comprises an electrically operated pump for positively pressurizing said portion to a predetermined positive pressure, a check valve between said portion and said pump for preventing loss of positive pressure from said portion back through said pump, a pressure switch for detecting the pressure in said portion, and means operatively relating said canister purge solenoid valve, said pressure switch, said pump, and said computer such that a diagnostic test to confirm the integrity of said portion against unacceptable leakage comprises said computer causing said canister purge solenoid valve to be operated closed and said pump to build positive pressure in said portion, and when said pressure switch senses the pressure in said portion having been built to a predetermined positive pressure, said computer causing said pump to cease building positive pressure in said portion so that the positive pressure in said portion as trapped therein by said check valve at the time said pump ceases building positive pressure is essentially equal to said predetermined positive pressure, and if pressure in said portion decreases from said predetermined positive pressure by a certain amount within a certain amount of time indicative of unacceptable leakage from said portion, said pressure switch giving to said computer a signal to indicate such unacceptable leakage.

5. The improvement set forth in claim 4 in which said pressure switch comprises a set of switch contacts that operate from one state to another state upon said pressure in said portion having built to said predetermined positive pressure and that operate back to said one state when pressure in said portion decreases from said predetermined positive pressure by a certain amount within a certain amount of time indicative of unacceptable leakage from said portion, said signal to said computer to indicate such unacceptable leakage being the operation of said set of switch contacts from said another state back to said one state.

6. The improvement set forth in claim 5 in which the operation of said set of switch contacts from said one state to said another state causes said computer to cause the operation of said pump to terminate.

7. 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, 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 intake manifold and that is under the control of said engine management computer, the improvement characterized by an associated diagnostic system that detects unacceptable leakage from a portion of the evaporative emission control system which portion includes said canister and tank and that comprises an electrically operated pump for positively pressurizing said portion to a predetermined positive pressure, a check valve between said portion and said pump for preventing loss of positive pressure from said portion back through said pump, a pressure switch for detecting the pressure in said portion, and means operatively relating said canister purge solenoid valve, said pressure switch, said pump, and said computer such that a diagnostic test to confirm the integrity of said portion against unacceptable leakage comprises said computer causing said canister purge solenoid valve to be operated closed and said pump to build positive pressure in said portion, and if said pressure switch fails to sense the pressure in said portion having been built to a predetermined positive pressure within a predetermined time, said computer indicating unacceptable leakage in said portion.

8. 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 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 an associated diagnostic system that detects unacceptable leakage from a portion of the canister purge system, which portion includes said canister and tank, and that comprises an electrically operated pump for creating a certain initial pressure in said portion at the beginning of a test and then ensealing said portion, detecting means for detecting change in the pressure in said portion from said initial pressure indicative of unacceptable leakage from said portion, and signaling means for giving a signal indicative of the detection of such change.

9. A canister purge system as set forth in claim 8 characterized further in that said initial pressure is a positive pressure.

10. A canister purge system as set forth in claim 8 characterized further in that said detecting means and said signaling means collectively comprise a pressure switch having a set of switch contacts.

11. 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 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 an associated diagnostic system that confirms the absence of unacceptable leakage from a portion of the canister purge system, which portion includes said canister and tank, and that comprises means for positively pressurizing said portion to a predetermined positive pressure, detecting means for detecting the absence of a certain decrease in the positive pressure in said portion from said predetermined positive pressure, which decrease is indicative of unacceptable leakage from said portion, and signaling means for giving a signal indicative of the absence of such decrease.

12. A canister purge system as set forth in claim 11 characterized further in that said means for positively pressurizing said portion to a predetermined positive pressure comprises an electrically operated pump.

13. A canister purge system as set forth in claim 11 characterized further in that said detecting means and said signaling means collectively comprise a pressure switch having a set of electrical contacts.

14. 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 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 an associated diagnostic system that confirms the absence of unacceptable leakage from a portion of the canister purge system, which portion includes said canister and tank, and that comprises an electrically operated pump for creating a certain initial pressure in said portion at the beginning of a test and then ensealing said portion, detecting means for detecting the absence of change in the pressure in said portion from said initial pressure, which change is indicative of unacceptable leakage from said portion, and signaling means for giving a signal indicative of the absence of such change.

15. A canister purge system as set forth in claim 14 characterized further in that said initial pressure is a positive pressure.

16. A canister purge system as set forth in claim 14 characterized further in that said detecting means and said signaling means collectively comprise a pressure switch having a set of switch contacts.

17. 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 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, detecting a certain decrease in the positive pressure in said portion from said predetermined positive pressure indicative of unacceptable leakage from said portion, and giving a signal indicative of such decrease.

18. 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 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 creating by means of an electrically operated pump a certain initial pressure in said portion at the beginning of a test and then ensealing said portion, detecting change in the pressure in said portion from said initial pressure indicative of unacceptable leakage from said portion, and giving a signal indicative of the detection of such change.

19. 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 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, detecting the absence of a certain decrease in the positive pressure in said portion from said predetermined positive pressure, which certain decrease is indicative of unacceptable leakage from said portion, and giving a signal indicative of the absence of such decrease.

20. 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 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 that confirms the absence of unacceptable leakage from a portion of the canister purge system, which portion includes said canister and tank, and that comprises creating by means of an electrically operated pump a certain initial pressure in said portion at the beginning of a test and then ensealing said portion, detecting the absence of change in the pressure in said portion from said initial pressure, which certain change is indicative of unacceptable leakage from said portion, and giving a signal indicative of the absence of such change.