Method and apparatus for detecting abnormal state of evaporative emission-control system

• US 5,203,870 A
• Filed: 06/26/1991
• Issued: 04/20/1993
• Est. Priority Date: 06/28/1990
• Status: Expired due to Fees

• Current Assignee: Toyota Jidosha Kabushiki Kaisha (Toyota Motor Corporation)
• Original Assignee: Toyota Jidosha Kabushiki Kaisha (Toyota Motor Corporation)
• Inventors: Otsuka, Takayuki, Uchida, Kenichi, Kayanuma, Nobuaki
• Primary Examiner(s): Miller, Carl Stuart
• Application Number:
  US07/721,687
• Time in Patent Office: 664 Days
• Field of Search: 123/516, 123/518, 123/519, 123/520, 123/521, 123/198 D, 123/479
• US Class Current: 123/198.00D
• CPC Class Codes: F02M 2025/0845 Electromagnetic valves
• CPC Class Codes: F02M 25/0809 Judging failure of purge control system

Abstract

In an evaporative emission-control system having a canister for trapping a fuel-vapor evaporated from the fuel tank and a purge control valve for executing a purging, an amount of fuel-vapor trapped in the canister is measured while the engine is stopped or in an idle state. The trapped fuel-vapor is purged from the canister and mixed with an air-fuel mixture when the amount of fuel-vapor trapped in the canister is sufficient for diagnosis while the vehicle is running in a predetermined driving condition. In this purge operation, a concentration of a vapor-laden air from the canister is measured and the occurrence of an abnormal state of the evaporative emission-control system is determined when a change of the concentration of the vapor-laden air after the purging is less than a predetermined value.

Claims

1. A method of detecting an abnormal state of an evaporative emission-control system in which a fuel-vapor evaporated from the fuel tank is temporarily trapped in a canister when an internal combustion engine is stopped or in an idle state, the trapped fuel-vapor is purged from the canister by a vacuum in a air-intake passage of the engine, and the purged fuel-vapor is mixed with an air-fuel mixture to be burned in a combustion chamber when a vehicle is running in a predetermined driving condition, comprising the steps of:

detecting an amount of fuel-vapor trapped in the canister, wherein the detection of the amount of fuel-vapor trapped in the canister is carried out by counting the time period for which fuel-vapor flows into the canister;

purging the fuel-vapor trapped in the canister and mixing the purged fuel-vapor with the air-fuel mixture in an air-intake passage;

detecting a concentration of a vapor-laden air from the canister when the purging is executed; and

determining the occurrence of an abnormal state of the evaporate emission-control system when the amount of fuel-vapor trapped in the canister is more than a predetermined amount, purging of the fuel-vapor trapped in the canister is executed, and a change of the concentration of the vapor-laden air from the canister before and after the purging is less than a predetermined value.

2. A method as set forth in claim 1, wherein the detection of the concentration of the vapor-laden air from the canister is carried out by a fuel gas sensor disposed downstream of a purge port in the air-intake passage.

3. A method as set forth in claim 1, wherein the detection of the concentration of the vapor-laden air from the canister is carried out by a fuel gas sensor disposed downstream of a purge port in the air-intake passage.

4. A method as set forth in claim 1, further comprising the step of prohibiting an execution of a diagnosis of the evaporative emission-control system when the amount of fuel-vapor trapped in the canister is less than a predetermined amount.

5. A method as set forth in claim 4, wherein the detection of the amount of fuel-vapor trapped in the canister is carried out by counting a time for which the purging is not executed, and prohibiting a diagnosis of the evaporative emission-control system when a difference between the time for which the purging is not executed and a time for which the purging is executed is less than a predetermined time.

6. A method as set forth in claim 5, wherein the detection of the concentration of the vapor-laden air from the canister is carried out by a fuel gas sensor disposed downstream of a purge port in the air-intake passage.

7. A method of detecting an abnormal state of an evaporative emission-control system in which a fuel-vapor evaporated from the fuel tank is temporarily trapped in a canister when an internal combustion engine is stopped or in an idle state, the trapped fuel-vapor is purged from the canister by a vacuum in a air-intake passage of the engine, and the purged fuel-vapor is mixed with an air-fuel mixture to be burned in a combustion chamber when a vehicle is running in a predetermined driving condition, comprising the steps of:

detecting an amount of fuel-vapor trapped in the canister, wherein the detection of the amount of fuel-vapor trapped in the canister is carried out by counting the time period for which fuel-vapor flows into the canister;

purging the fuel-vapor trapped in the canister and mixing the purged fuel-vapor with the air-fuel mixture in an air-intake passage;

detecting a concentration of a vapor-laden air from the canister when the purging is executed; and

determining the occurrence of an abnormal state of the evaporative emission-control system when the amount of fuel-vapor trapped in the canister is more than a predetermined amount, purging of the fuel-vapor trapped in the canister is executed, and the detected concentration of a vapor-laden air is smaller than the calculated concentration of a vapor-laden air in accordance with the amount of fuel-vapor trapped in the canister.

8. A method as set forth in claim 7, wherein the detection of the concentration of the vapor-laden air from the canister is carried out by a fuel gas sensor disposed downstream of a purge port in the air-intake passage.

9. A method as set forth in claim 7, wherein the detection of the concentration of the vapor-laden air from the canister is carried out by a fuel gas sensor disposed downstream of a purge port in the air-intake passage.

10. A method as set forth in claim 7, further comprising the step of prohibiting an execution of a diagnosis of the evaporative emission-control system when the amount of fuel-vapor trapped in the canister is less than a predetermined amount.

11. A method as set forth in claim 10, wherein the detection of the amount of fuel-vapor trapped in the canister is carried out by counting a time for which the purging is not executed, and prohibiting a diagnosis of the evaporative emission-control system when a difference between the time for which the purging is not executed and a time for which the purging is executed is less than a predetermined time.

12. A method as set forth in claim 11, wherein the detection of the concentration of the vapor-laden air from the canister is carried out by a fuel gas sensor disposed downstream of a purge port in the air-intake passage.

13. An apparatus for detecting an abnormal state of an evaporative emission-control system in which a fuel-vapor evaporated from the fuel tank is temporarily trapped in a canister when an internal combustion engine is stopped or in an idle state, the trapped fuel-vapor is purged from the canister by a vacuum in a air-intake passage of the engine, and the purged fuel-vapor is mixed with an air-fuel mixture to be burned in a combustion chamber when a vehicle is running in a predetermined driving condition, comprising:

means for detecting an amount of fuel-vapor trapped in the canister, wherein the detection of the amount of fuel-vapor trapped in the canister is carried out by counting the time period for which fuel-vapor flows into the canister;

means for purging the fuel-vapor trapped in the canister and mixing the purged fuel-vapor with the air-fuel mixture in an air-intake passage;

means for detecting a concentration of a vapor-laden air from the canister when the purging is executed; and

means for determining the occurrence of an abnormal state of the evaporative emission-control system when the amount of fuel-vapor trapped in the canister is more than a predetermined amount, purging of the fuel-vapor trapped in the canister is executed, and a change of the concentration of the vapor-laden air from the canister before and after the purging is less than a predetermined value.

14. An apparatus as set forth in claim 13, wherein the detection of the concentration of the vapor-laden air from the canister is carried out by a fuel gas sensor disposed downstream of a purge port in the air-intake passage.

15. An apparatus as set forth in claim 13, wherein the detection of the concentration of the vapor-laden air from the canister is carried out by a fuel gas sensor disposed downstream of a purge port in the air-intake passage.

16. An apparatus as set forth in claim 13, further comprising means for prohibiting an execution of a diagnosis of the evaporative emission-control system when the amount of fuel-vapor trapped in the canister is less than a predetermined amount.

17. An apparatus as set forth in claim 16, wherein the detection of the amount of fuel-vapor trapped in the canister is carried out by counting a time for which the purging is not executed, and prohibiting a diagnosis of the evaporative emission-control system when a difference between the time for which the purging is not executed and a time for which the purging is executed is less than a predetermined time.

18. An apparatus as set forth in claim 17, wherein the detection of the concentration of the vapor-laden air from the canister is carried out by a fuel gas sensor disposed downstream of a purge port in the air-intake passage.

19. An apparatus for detecting an abnormal state of an evaporative emission-control system in which a fuel-vapor evaporated from the fuel tank is temporarily trapped in a canister when an internal combustion engine is stopped or in an idle state, the trapped fuel-vapor is purged from the canister by a vacuum in a air-intake passage of the engine, and the purged fuel-vapor is mixed with an air-fuel mixture to be burned in a combustion chamber when a vehicle is running in a predetermined driving condition, comprising:

means for detecting an amount of fuel-vapor trapped in the canister, wherein the detection of the amount of fuel-vapor trapped in the canister is carried out by counting the time period for which the fuel-vapor flows into the canister;

means for purging the fuel-vapor trapped in the canister and mixing the purged fuel-vapor with the air-fuel mixture in an air-intake passage;

means for detecting a concentration of a vapor-laden air from the canister when the purging is executed; and

means for determining the occurrence of an abnormal state of the evaporative emission-control system when the amount of fuel-vapor trapped in the canister is more than a predetermined amount, purging of the fuel vapor trapped in the canister is executed, and the detected concentration of a vapor-laden air is smaller than the calculated concentration of a vapor-laden air in accordance with the amount of fuel-vapor trapped in the canister.

20. An apparatus as set forth in claim 19, wherein the detection of the concentration of the vapor-laden air from the canister is carried out by a fuel gas sensor disposed downstream of a purge port in the air-intake passage.

21. An apparatus as set forth in claim 19, wherein the detection of the concentration of the vapor-laden air from the canister is carried out by a fuel gas sensor disposed downstream of a purge port in the air-intake passage.

22. An apparatus as set forth in claim 19, further comprising means for prohibiting an execution of a diagnosis of the evaporative emission-control system when the amount of fuel-vapor trapped in the canister is less than a predetermined amount.

23. An apparatus as set forth in claim 22, wherein the detection of the amount of fuel-vapor trapped in the canister is carried out by counting a time for which the purging is not executed, and prohibiting a diagnosis of the evaporative emission-control system when a difference between the time for which the purging is not executed and a time for which the purging is executed is less than a predetermined time.

24. An apparatus as set forth in claim 23, wherein the detection of the concentration of the vapor-laden air from the canister is carried out by a fuel gas sensor disposed downstream of a purge port in the air-intake passage.