Diagnosis apparatus for fuel vapor purge system and method thereof

1. A diagnosis apparatus for a fuel vapor purge system which traps the fuel vapor generated in a fuel tank to a canister, to purge the fuel vapor trapped to said canister to an intake passage of an internal combustion engine, comprising:

a pressure generator forcibly changing a pressure in a shielded purge passage inclusive of said fuel tank;

a pressure detector detecting the pressure in said purge passage; and

a diagnosis device forcibly changing the pressure in said purge passage by said pressure generator and also receiving a detection signal from said pressure detector, to diagnose whether or not the leakage occurs in said purge passage,

wherein said diagnosis device starts the diagnosis processing from a standby period that has elapsed after an operation of said internal combustion engine was stopped, and

wherein said diagnosis device calculates a standby time defining the standby period when said internal combustion engine has been stopped, and starts said diagnosis processing from said standby time that has elapsed after the operation of said internal combustion engine was stopped.

2. A diagnosis apparatus for a fuel vapor purge system according to claim 1 , further comprising:

a fuel temperature detector detecting a fuel temperature in said fuel tank,

wherein said diagnosis device calculates said standby time based on the fuel temperature detected by said fuel temperature detector.

3. A diagnosis apparatus for a fuel vapor purge system according to claim 1 , further comprising:

a fuel temperature estimator estimating a fuel temperature in said fuel tank,

wherein said diagnosis device calculates said standby time based on the fuel temperature estimated by said fuel temperature estimator.

4. A diagnosis apparatus for a fuel vapor purge system according to claim 1 , further comprising:

a fuel property detector detecting a fuel property in said fuel tank,

wherein said diagnosis device calculates said standby time based on the fuel property detected by said fuel property detector.

5. A diagnosis apparatus for a fuel vapor purge system according to claim 1 , further comprising:

a fuel level detector detecting a fuel level in said fuel tank,

wherein said diagnosis device calculates said standby time based on the fuel level detected by said fuel level detector.

6. A diagnosis apparatus for a fuel vapor purge system according to claim 1 , further comprising:

an environmental condition detector detecting environmental conditions of said internal combustion engine,

wherein said diagnosis device calculates said standby time based on the environmental conditions of said internal combustion engine detected by said environmental condition detector.

7. A diagnosis apparatus for a fuel vapor purge system according to claim 1 , wherein said diagnosis device calculates said standby time based on the pressure detected by said pressure detector.

8. A diagnosis apparatus for a fuel vapor purge system which traps the fuel vapor generated in a fuel tank to a canister, to purge the fuel vapor trapped to said canister to an intake passage of an internal combustion engine, comprising:

a pressure generator forcibly changing a pressure in a shielded purge passage inclusive of said fuel tank:

a pressure detector detecting the pressure in said purge passage;

a diagnosis device forcibly changing the pressure in said purge passage by said pressure generator and also receiving a detection signal from said pressure detector, to diagnose whether or not the leakage occurs in said purge passage; and

a diagnosis start condition detector detecting a diagnosis start condition,

wherein said diagnosis device starts the diagnosis processing from a standby period that has elapsed after an operation of said internal combustion engine was stopped,

wherein said diagnosis device sets a period until said diagnosis start condition is detected after the operation of said internal combustion engine has been stopped, as said standby period, and

wherein said diagnosis start condition detector:

includes an environmental temperature detector detecting an environmental temperature of fuel, and

detects that said environmental temperature becomes lower than a threshold after the operation of said internal combustion engine has been stopped, as said diagnosis start condition.

9. A diagnosis apparatus for a fuel vapor purge system which traps the fuel vapor generated in a fuel tank to a canister, to purge the fuel vapor trapped to said canister to an intake passage of an internal combustion engine, comprising:

a pressure generator forcibly changing a pressure in a shielded purge passage inclusive of said fuel tank;

a pressure detector detecting the pressure in said purge passage;

a diagnosis device forcibly changing the pressure in said purge passage by said pressure generator and also receiving a detection signal from said pressure detector, to diagnose whether or not the leakage occurs in said purge passage; and

a diagnosis start condition detector detecting a diagnosis start condition,

wherein said diagnosis device starts the diagnosis processing from a standby period that has elapsed after an operation of said internal combustion engine was stopped,

wherein said diagnosis device sets a period until said diagnosis start condition is detected after the operation of said internal combustion engine has been stopped, as said standby period, and

wherein said diagnosis start condition detector:

includes a fuel temperature detector detecting a fuel temperature in said fuel tank, and

detects that said fuel temperature becomes lower than a threshold after the operation of said internal combustion engine has been stopped, as said diagnosis start condition.

10. A diagnosis apparatus for a fuel vapor purge system which traps the fuel vapor generated in a fuel tank to a canister, to purge the fuel vapor trapped to said canister to an intake passage of an internal combustion engine, comprising:

a pressure generator forcibly changing a pressure in a shielded purge passage inclusive of said fuel tank;

a pressure detector detecting the pressure in said purge passage;

a diagnosis device forcibly changing the pressure in said purge passage by said pressure generator and also receiving a detection signal from said pressure detector, to diagnose whether or not the leakage occurs in said purge passage; and

a diagnosis start condition detector detecting a diagnosis start condition.

wherein said diagnosis device starts the diagnosis processing from a standby period that has elapsed after an operation of said internal combustion engine was stopped,

wherein said diagnosis device sets a period until said diagnosis start condition is detected after the operation of said internal combustion engine has been stopped, as said standby period, and

wherein said diagnosis start condition detector detects that the pressure detected by said pressure detector becomes lower than a threshold after the operation of said internal combustion engine has been stopped, as said diagnosis start condition.

11. A diagnosis method for a fuel vapor purge system which traps the fuel vapor generated in a fuel tank to a canister, to purge the fuel vapor trapped to said canister to an intake passage of an internal combustion engine, comprising the steps of:

judging whether or not a standby period has elapsed after an operation of said internal combustion engine was stopped;

forcibly changing a pressure in a shielded purge passage inclusive of said fuel tank after said standby period has elapsed;

detecting the pressure in said purge passage;

diagnosing whether or not the leakage occurs in said purge passage, based on the detected pressure; and

calculating a standby time defining said standby period, by:

detecting a fuel temperature in said fuel tank, and

calculating said standby time based on the detected fuel temperature.

12. A diagnosis method for a fuel vapor purge system which traps the fuel vapor generated in a fuel tank to a canister, to purge the fuel vapor trapped to said canister to an intake passage of an internal combustion engine, comprising the steps of:

judging whether or not a standby period has elapsed after an operation of said internal combustion engine was stopped;

forcibly changing a pressure in a shielded purge passage inclusive of said fuel tank after said standby period has elapsed;

detecting the pressure in said purge passage;

diagnosing whether or not the leakage occurs in said purge passage, based on the detected pressure; and

calculating a standby time defining said standby period, by:

estimating a fuel temperature in said fuel tank; and

calculating said standby time based on the estimated fuel temperature.

13. A diagnosis method for a fuel vapor purge system which traps the fuel vapor generated in a fuel tank to a canister, to purge the fuel vapor trapped to said canister to an intake passage of an internal combustion engine, comprising the steps of:

judging whether or not a standby period has elapsed after an operation of said internal combustion engine was stopped;

forcibly changing a pressure in a shielded purge passage inclusive of said fuel tank after said standby period has elapsed;

detecting the pressure in said purge passage;

diagnosing whether or not the leakage occurs in said purge passage, based on the detected pressure; and

calculating a standby time defining said standby period, by:

detecting a fuel property in said fuel tank; and

calculating said standby time based on the detected fuel property.

14. A diagnosis method for a fuel vapor purge system which traps the fuel vapor generated in a fuel tank to a canister, to purge the fuel vapor trapped to said canister to an intake passage of an internal combustion engine, comprising the steps of:

judging whether or not a standby period has elapsed after an operation of said internal combustion engine was stopped;

forcibly changing a pressure in a shielded purge passage inclusive of said fuel tank after said standby period has elapsed;

detecting the pressure in said purge passage;

diagnosing whether or not the leakage occurs in said purge passage, based on the detected pressure; and

calculating a standby time defining said standby period, by:

detecting a fuel level in said fuel tank; and

calculating said standby time based on the detected fuel level.

15. A diagnosis method for a fuel vapor purge system which traps the fuel vapor generated in a fuel tank to a canister, to purge the fuel vapor trapped to said canister to an intake passage of an internal combustion engine, comprising the steps of:

judging whether or not a standby period has elapsed after an operation of said internal combustion engine was stopped;

forcibly changing a pressure in a shielded purge passage inclusive of said fuel tank after said standby period has elapsed;

detecting the pressure in said purge passage;

diagnosing whether or not the leakage occurs in said purge passage, based on the detected pressure; and

calculating a standby time defining said standby period, by:

detecting environmental conditions of said internal combustion engine; and

calculating said standby time based on the detected environmental conditions.

16. A diagnosis method for a fuel vapor purge system which traps the fuel vapor generated in a fuel tank to a canister, to purge the fuel vapor trapped to said canister to an intake passage of an internal combustion engine, comprising the steps of:

judging whether or not a standby period has elapsed after an operation of said internal combustion engine was stopped;

forcibly changing a pressure in a shielded purge passage inclusive of said fuel tank after said standby period has elapsed;

detecting the pressure in said purge passage;

diagnosing whether or not the leakage occurs in said purge passage, based on the detected pressure; and

calculating a standby time defining said standby period, by:

detecting the pressure in said purge passage; and

calculating said standby time based on the detected pressure.

17. A diagnosis method for a fuel vapor purge system which traps the fuel vapor generated in a fuel tank to a canister, to purge the fuel vapor trapped to said canister to an intake passage of an internal combustion engine, comprising the steps of:

judging whether or not a standby period has elapsed after an operation of said internal combustion engine was stopped;

forcibly changing a pressure in a shielded purge passage inclusive of said fuel tank after said standby period has elapsed;

detecting the pressure in said purge passage; and

diagnosing whether or not the leakage occurs in said purge passage, based on the detected pressure,

wherein said step of judging whether or not the standby period has elapsed comprises the steps of:

detecting a diagnosis start condition; and

judging that said standby period has elapsed, at the time when said diagnosis start condition is detected after the operation of said internal combustion engine has been stopped, and

wherein said step of detecting the diagnosis start condition comprises the steps of:

detecting an environmental temperature of fuel; and

judging whether or not said environmental temperature becomes lower than a threshold after the operation of said internal combustion engine has been stopped.

18. A diagnosis method for a fuel vapor purge system which traps the fuel vapor generated in a fuel tank to a canister, to purge the fuel vapor trapped to said canister to an intake passage of an internal combustion engine, comprising the steps of:

judging whether or not a standby period has elapsed after an operation of said internal combustion engine was stopped;

forcibly changing a pressure in a shielded purge passage inclusive of said fuel tank after said standby period has elapsed;

detecting the pressure in said purge passage; and

diagnosing whether or not the leakage occurs in said purge passage, based on the detected pressure,

wherein said step of judging whether or not the standby period has elapsed comprises the steps of:

detecting a diagnosis start condition; and

judging that said standby period has elapsed, at the time when said diagnosis start condition is detected after the operation of said internal combustion engine has been stopped, and

wherein said step of detecting the diagnosis start condition comprises the steps of:

detecting a fuel temperature in said fuel tank; and

judging whether or not said fuel temperature becomes lower than a threshold after the operation of said internal combustion engine has been stopped.

19. A diagnosis method for a fuel vapor purge system which traps the fuel vapor generated in a fuel tank to a canister, to purge the fuel vapor trapped to said canister to an intake passage of an internal combustion engine, comprising the steps of:

judging whether or not a standby period has elapsed after an operation of said internal combustion engine was stopped;

forcibly changing a pressure in a shielded purge passage inclusive of said fuel tank after said standby period has elapsed;

detecting the pressure in said purge passage; and

diagnosing whether or not the leakage occurs in said purge passage, based on the detected pressure,

wherein said step of judging whether or not the standby period has elapsed comprises the steps of:

detecting a diagnosis start condition; and

judging that said standby period has elapsed, at the time when said diagnosis start condition is detected after the operation of said internal combustion engine has been stopped, and

wherein said step of detecting the diagnosis start condition comprises the steps of:

detecting the pressure in said purge passage; and

judging whether or not said pressure becomes lower than a threshold after the operation of said internal combustion engine has been stopped.