Leakage diagnosis apparatus for fuel vapor purge system and method thereof

• US 20040250604A1
• Filed: 06/14/2004
• Published: 12/16/2004
• Est. Priority Date: 06/16/2003
• Status: Active Grant

• Current Assignee: Hitachi, Ltd.
• Original Assignee: Hitachi Unisia Automotive, Ltd. (Hitachi, Ltd.)
• Inventors: Watanabe, Satoru, Hosoya, Hajime
• Granted Patent: US 6,966,214 B2
• Time in Patent Office: Days
• US Class Current: 73/49.2
• CPC Class Codes: F02M 25/0809 Judging failure of purge control system

Abstract

In a fuel vapor purge system, an occurrence of leakage in a diagnosis zone is diagnosed, based on data indicating a pressure rise characteristic in the diagnosis zone for when the diagnosis zone is pressurized, and data indicating a pressure drop characteristic in the diagnosis zone after the pressurization of the diagnosis zone is stopped.

Claims

1. A leakage diagnosis apparatus for a fuel vapor purge system, in which fuel vapor generated in a fuel tank is trapped in a canister via an evaporation passage, and the fuel vapor trapped in said canister is purged, via a purge passage, into an intake passage of an internal combustion engine, comprising:

a blocking device blocking a diagnosis zone containing at least one of said fuel tank, said evaporation passage, said canister and said purge passage;

a pressurizer pressurizing said diagnosis zone;

a pressure detector detecting the pressure in said diagnosis zone; and

a diagnosis unit that outputs control signals to said blocking device and said pressurizer, and also receives a detection signal from said pressure detector, to diagnose an occurrence of leakage in said diagnosis zone,

wherein said diagnosis unit blocks said diagnosis zone by said blocking device, and detects data indicating a pressure rise characteristic in said diagnosis zone for when said diagnosis zone is pressurized by said pressurizer based on the detection signal from said pressure detector and also detects data indicating a pressure drop characteristic in said diagnosis zone after the pressurization by said pressurizer is stopped, and diagnoses an occurrence of leakage in said diagnosis zone based on the data indicating said pressure rise characteristic and the data indicating said pressure drop characteristic.

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

wherein said diagnosis unit;

detects a pressure rise amount within a first period of time after the pressurization by said pressurizer is started, as the data indicating said pressure rise characteristic, and detects a pressure drop amount within a second period of time after the pressurization by said pressurizer is stopped, as the data indicating said pressure drop characteristic.

3. A leakage diagnosis apparatus for a fuel vapor purge system according to claim 2,

wherein said diagnosis unit:

judges that there is no leakage, when said pressure rise amount is larger than a first threshold, and also said pressure drop amount is smaller than a second threshold;

judges an occurrence of leakage when said pressure rise amount is equal to or less than the first threshold; and

judges an occurrence of leakage when said pressure drop amount is equal to or larger than the second threshold.

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

wherein, said diagnosis unit;

detects the curvature of a pressure change curve during the pressurization by said pressurizer as the data indicating said pressure rise characteristic, and detects a pressure drop amount within a second period of time after the stop of pressurization by said pressurizer as the data indicating said pressure drop characteristic.

5. A leakage diagnosis apparatus for a fuel vapor purge system according to claim 4,

wherein said diagnosis unit;

judges that there is no leakage, when an absolute value of said curvature is smaller than a third threshold, and also said pressure drop amount is smaller than a second threshold;

judges an occurrence of leakage when the absolute value of said curvature is equal to or larger than the third threshold; and

judges an occurrence of leakage when said pressure drop amount is equal to or larger than the second threshold.

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

a remaining quantity detector detecting a remaining fuel quantity in said fuel tank,

wherein said blocking device blocks a diagnosis zone containing said fuel tank, and

said diagnosis unit corrects the data indicating said pressure rise characteristic and the data indicating said pressure drop characteristic based on said remaining fuel quantity detected by said remaining quantity detector, to diagnose an occurrence of leakage based on said corrected data.

7. A leakage diagnosis apparatus for a fuel vapor purge system according to claim 1, further comprising;

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

wherein said blocking device blocks a diagnosis zone containing said fuel tank, and

said diagnosis unit corrects the data indicating said pressure rise characteristic and the data indicating said pressure drop characteristic based on the fuel property detected by said fuel property detector, to diagnose an occurrence of leakage based on said corrected data.

8. A leakage diagnosis apparatus for a fuel vapor purge system according to claim 7,

wherein said fuel property detector;

detects said fuel property based on the data indicating said pressure rise characteristic in said diagnosis zone due to the fuel vapor for when said diagnosis zone is blocked by said blocking device.

9. A leakage diagnosis apparatus for a fuel vapor purge system according to claim 1,

wherein said blocking device:

blocks a diagnosis zone containing said fuel tank; and

comprises a remaining quantity detector detecting a remaining fuel quantity in said fuel tank, and

said diagnosis unit suspends the diagnosis of occurrence of leakage when said remaining fuel quantity is equal to or less than a predetermined amount.

10. A leakage diagnosis apparatus for a fuel vapor purge system according to claim 1,

wherein said blocking device:

blocks a diagnosis zone containing said fuel tank; and

comprises a remaining quantity detector detecting a remaining fuel quantity in said fuel tank, and

said diagnosis unit suspends the diagnosis of occurrence of leakage when said remaining fuel quantity is equal to or more than a second predetermined amount.

11. A leakage-diagnosis apparatus for a fuel vapor purge system according to claim 1,

wherein said blocking device blocks a diagnosis zone containing said fuel tank, and

said diagnosis unit;

suspends the diagnosis of occurrence of leakage when a pressure rise amount in said diagnosis zone due to the fuel vapor for when said diagnosis zone is blocked by said blocking device, does not reach a predetermined value within a third period of time.

12. A leakage diagnosis apparatus for a fuel vapor purge system, in which fuel vapor generated in a fuel tank is trapped in a canister via an evaporation passage, and the fuel vapor trapped in said canister is purged, via a purge passage, into an intake passage of an internal combustion engine, comprising:

means for blocking a diagnosis zone containing at least one of said fuel tank, said evaporation passage, said canister and said purge passage;

means for pressurizing said diagnosis zone;

means for detecting the pressure in said diagnosis zone;

means for detecting data indicating a pressure rise characteristic in said diagnosis zone for when said diagnosis zone is pressurized in a state where said diagnosis zone is blocked;

means for detecting data indicating a pressure drop characteristic in said diagnosis zone after the pressurization of said diagnosis zone is stopped; and

means for diagnosing an occurrence of leakage in said diagnosis zone based on the data indicating said pressure rise characteristic and the data indicating said pressure drop characteristic.

13. A leakage diagnosis method for a fuel vapor purge system, in which fuel vapor generated in a fuel tank is trapped in a canister via an evaporation passage, and the fuel vapor trapped in said canister is purged, via a purge passage, into an intake passage of an internal combustion engine, comprising the steps of:

blocking a diagnosis zone containing at least one of said fuel tank, said evaporation passage, said canister and said purge passage;

pressurizing said diagnosis zone;

detecting the pressure in said diagnosis zone;

detecting data indicating a pressure rise characteristic in said diagnosis zone for when said diagnosis zone is pressurized in a state where said diagnosis zone is blocked;

detecting data indicating a pressure drop characteristic in said diagnosis zone after the pressurization of said diagnosis zone is stopped; and

diagnosing an occurrence of leakage in said diagnosis zone based on the data indicating said pressure rise characteristic and the data indicating said pressure drop characteristic.

14. A leakage diagnosis method for a fuel vapor purge system according to claim 13,

wherein said step of detecting the pressure rise characteristic;

detects a pressure rise amount within a first period of time after the pressurization of said diagnosis zone is started, as the data indicating said pressure rise characteristic, and

said step of detecting the pressure drop characteristic;

detects a pressure drop amount within a second period of time after the pressurization of said diagnosis zone is stopped, as the data indicating said pressure drop characteristic.

15. A leakage diagnosis method for a fuel vapor purge system according to claim 14,

wherein said step of diagnosing an occurrence of leakage comprises the steps of:

judging that there is no leakage, when said pressure rise amount is larger than a first threshold, and also said pressure drop amount is smaller than a second threshold;

judging an occurrence of leakage when said pressure rise amount is equal to or less than the first threshold; and

judging an occurrence of leakage when said pressure drop amount is equal to or larger than the second threshold.

16. A leakage diagnosis method for a fuel vapor purge system according to claim 13,

wherein, said step of detecting the data indicating said pressure rise characteristic;

detects the curvature of a pressure change curve during the pressurization of said diagnosis zone as the data indicating said pressure rise characteristic, and

said step of detecting the data indicating said pressure drop characteristic;

detects a pressure drop amount within a second period of time after the stop of pressurization of said diagnosis zone.

17. A leakage diagnosis method for a fuel vapor purge system according to claim 16,

wherein said step of diagnosing an occurrence of leakage comprises the steps of;

judging that there is no leakage, when an absolute value of said curvature is smaller than a third threshold, and also said pressure drop amount is smaller than a second threshold;

judging an occurrence of leakage when the absolute value of said curvature is equal to or larger than the third threshold; and

judging an occurrence of leakage when said pressure drop amount is equal to or larger than the second threshold.

18. A leakage diagnosis method for a fuel vapor purge system according to claim 13,

wherein said step of blocking the diagnosis zone blocks a diagnosis zone containing said fuel tank, and

further comprises the steps of:

detecting a remaining fuel quantity in said fuel tank; and

correcting the data indicating said pressure rise characteristic and the data indicating said pressure drop characteristic based on said remaining fuel quantity.

19. A leakage diagnosis method for a fuel vapor purge system according to claim 13,

wherein said step of blocking the diagnosis zone blocks a diagnosis zone containing said fuel tank, and

further comprising the steps of:

detecting a property of fuel in said fuel tank; and

correcting the data indicating said pressure rise characteristic and the data indicating said pressure drop characteristic based on said fuel property.

20. A leakage diagnosis method for a fuel vapor purge system according to claim 19,

wherein said step of detecting the property of fuel further comprises the steps of:

detecting the data indicating said pressure rise characteristic in said diagnosis zone due to the fuel vapor for when said diagnosis zone is blocked; and

detecting said fuel property based on the data indicating said pressure rise characteristic due to the fuel vapor.

21. A leakage diagnosis method for a fuel vapor purge system according to claim 13,

wherein said step of blocking the diagnosis zone blocks a diagnosis zone containing said fuel tank, and

further comprises the steps of:

detecting a remaining fuel quantity in said fuel tank, and

suspending the diagnosis of occurrence of leakage when said remaining fuel quantity is equal to or less than a predetermined amount.

22. A leakage diagnosis method for a fuel vapor purge system according to claim 13,

wherein said step of blocking the diagnosis zone blocks a diagnosis zone containing said fuel tank, and

further comprises the steps of:

detecting a remaining fuel quantity in said fuel tank; and

suspending the diagnosis of occurrence of leakage when said remaining fuel quantity is equal to or larger than a second predetermined amount.

23. A leakage diagnosis method for a fuel vapor purge system according to claim 13,

wherein said step of blocking the diagnosis zone blocks a diagnosis zone containing said fuel tank, and

further comprises the step of;

suspending the diagnosis of occurrence of leakage when a pressure rise amount in said diagnosis zone due to the fuel vapor for when said diagnosis zone is blocked, does not reach a predetermined value within a third period of time.