More reliable leakage diagnosis for evaporated gas purge system

• US 6,192,742 B1
• Filed: 11/13/1998
• Issued: 02/27/2001
• Est. Priority Date: 11/17/1997
• Status: Expired due to Term

• Current Assignee: DENSO Corporation
• Original Assignee: DENSO Corporation
• Inventors: Miwa, Makoto, Majima, Yoshihiro
• Primary Examiner(s): Williams, Hezron
• Assistant Examiner(s): Politzer, Jay L.
• Application Number:
  US09/190,243
• Time in Patent Office: 837 Days
• Field of Search: 73/40, 731/181, 123/520
• US Class Current: 73/40
• CPC Class Codes: F02M 25/0809 Judging failure of purge control system

Abstract

To perform leak diagnosis, when it is determined (during engine idling) that leakage exists in the purge system air is reintroduced into a purge system. Then, determination of leakage existence is stopped. Accordingly, erroneous diagnosis caused by opening the filler cap during engine idling is prevented, and reliability of leakage diagnosis is improved.

Claims

1. A leakage diagnosing apparatus for an evaporated gas purge system having a fuel tank with a removable cap, an intake pipe for an engine, a passage which connects the fuel tank to the intake pipe, a canister installed in the passage for adsorbing evaporated gas, and a purge control valve installed in the passage for controlling a purge of said adsorbed evaporated gas from the canister to the intake pipe, said apparatus comprising:

leakage diagnosing means for diagnosing existence of leakage in the purge system by detecting at least one of;

(a) pressure in a part of the purge system at least including the fuel tank and the canister if said part of the purge system is hermetically sealed with said cap after introducing air therein, and (b) pressure change in said part of the purge system if it is hermetically sealed with said cap after introducing air therein;

means for reintroducing air into said part of the purge system when it is tentatively determined that leakage exists during idling of the engine; and

means for canceling said earlier tentative determination of leakage existence if it is determined that said cap likely was not sealed with the tank during the earlier diagnosis.

2. A leakage diagnosing apparatus for an evaporated gas purge system as in claim 1 wherein:

said means for canceling a prior tentative determination of leakage effects said cancellation when pressure in said part of the purge system after reintroduction of air does not reach a predetermined pressure within a predetermined time period.

3. A leakage diagnosing apparatus for an evaporated gas purge system as in claim 2 further comprising:

means for determining said predetermined time period based on at least one of;

(a) atmospheric pressure, (b) a learned value of concentration of evaporated gas, (c) fuel remaining in the fuel tank, (d) pressure of said part of the purge system before said reintroduction of air, and (e) pressure change in said part of the purge system during leakage diagnosis.

4. A leakage diagnosing apparatus for an evaporated gas purge system having a fuel tank with a removable cap, an intake pipe for an engine, a passage which connects the fuel tank to the intake pipe, a canister installed in the passage for adsorbing evaporated gas, and a purge control valve installed in the passage for controlling a purge of said adsorbed evaporated gas from the canister to the intake pipe, said apparatus comprising:

leakage diagnosing means for diagnosing existence of leakage in the purge system based on detecting at least one of;

(a) pressure in a part of the purge system at least including the fuel tank and the canister it said part of the purge system is hermetically sealed with said cap after introducing air therein, and (b) pressure change in said part of the purge system if it is hermetically sealed with said cap after introducing air therein;

fuel detecting means for detecting fuel remaining in said fuel tank;

means for determining whether said detected fuel remaining is increased; and

means for executing one of;

(a) stopping said leakage diagnosis and (b) canceling a current diagnosis of leakage existence, when it is determined that said cap likely was not sealed with the tank during said leak diagnosis because said detected fuel remaining amount is increased.

5. A leakage diagnosing apparatus for an evaporated gas purge system having a fuel tank with a removable cap, an intake pipe for an engine, a passage which connects the fuel tank to the intake pipe, a canister installed in the passage for adsorbing evaporated gas, and a purge control valve installed in the passage for controlling a purge of said adsorbed evaporated gas from the canister to the intake pipe, said apparatus comprising:

leakage diagnosing means for diagnosing existence of leakage in the purge system based on detecting at least one of;

(a) pressure in a part of the purge system at least including the fuel tank and the canister if said part of the purge system is hermetically sealed with said cap after introducing an air therein, and (b) pressure change in said part of the purge system if it is hermetically sealed with said cap after introducing air therein;

shift position detecting means for detecting a gear shift position of an automatic transmission;

means for determining whether said detected shift position is one of a neutral position and a parking position; and

means for executing one of;

(a) stopping said leakage diagnosis and (b) canceling a current diagnosis of leakage existence, when said detected shift position is one of said neutral position and said parking position.

6. A leakage diagnosing apparatus for an evaporated gas purge system having a fuel tank with a removable cap, an intake pipe for an engine, a passage which connects the fuel tank to the intake pipe, a canister installed in the passage for adsorbing evaporated gas, and a purge control valve installed in the passage for controlling a purge of said adsorbed evaporated gas from the canister to the intake pipe, said apparatus comprising:

leakage diagnosing means for determining existence of leakage in the purge system based on detecting at least one of;

(a) pressure in the purge system if the purge system is hermetically sealed with said cap after introducing one of a positive pressure and a negative pressure therein, and (b) pressure change in the purge system if the purge system is hermetically sealed with said cap after introducing one of a positive pressure and a negative pressure therein; and

means for operating said leakage diagnosing means again while a vehicle is running, if it determines that leakage exists in the purge system while said vehicle is stopped.

7. A leakage diagnosing apparatus for an evaporated gas purge system as in claim 6, wherein:

said leakage diagnosing means attempts to introduce negative pressure into the purge system again while an associated vehicle is running if said negative pressure was unable to be introduced into the purge system while said vehicle was stopped.

8. A leakage diagnosing apparatus for an evaporated gas purge system as in claim 7 wherein:

said leakage diagnosing means attempts to introduce negative pressure into the fuel tank again while a vehicle is running if negative pressure was unable to be introduced into the fuel tank while said vehicle was stopped.

9. A leakage diagnosing method for an evaporated gas purge system having a fuel tank with a removable cap, an intake pipe for an engine, a passage which connects the fuel tank to the intake pipe;

a canister installed in the passage for adsorbing evaporated gas, and a purge control valve installed in the passage for controlling a purge of said adsorbed evaporated gas from the canister to the intake pipe, said method comprising;

tentatively diagnosing existence of leakage in the purge system by detecting pressure or pressure change in at least a part of the purge system if it is hermetically sealed and air has been introduced therein;

reintroducing air into said part of the purge system when it is determined that leakage exists during an engine idling state; and

canceling the initial tentative determination of leakage existence after said reintroduction of air if it is determined that said cap likely was not sealed with the tank during the earlier diagnosis.

10. A leakage diagnosing method as in claim 9 wherein:

said canceling of a prior tentative determination of leakage occurs when a predetermined pressure is not reached within a predetermined time period during said reintroduction of air.

11. A leakage diagnosing method as in claim 10, wherein:

determining said predetermined time period is based on at least one of;

(a) atmospheric pressure, (b) a learned value of concentration of evaporated gas, (c) fuel remaining in the fuel tank, (d) pressure of said part of the purge system before said reintroduction of air, and (e) pressure change in said part of the purge system during leakage diagnosis.

12. A leakage diagnosing method for an evaporated gas purge system having a fuel tank with a removable cap, an intake pipe for an engine, a passage which connects the fuel tank to the intake pipe, a canister installed in the passage for adsorbing evaporated gas, and a purge control valve installed in the passage for controlling a purge of said adsorbed evaporated gas from the canister to the intake pipe, said method comprising:

diagnosing existence of leakage in the purge system based on detecting pressure or pressure change in a part of the purge system at least including the fuel tank and the canister if said part of the purge system is hermetically sealed with said cap after introducing air therein;

detecting fuel remaining in said fuel tank;

determining whether said detected fuel remaining is increased; and

stopping or canceling said leakage diagnosis if said detected fuel remaining amount is increased.

13. A leakage diagnosing method for an evaporated gas purge system having a fuel tank with a removable cap, an intake pipe for an engine, a passage which connects the fuel tank to the intake pipe, a canister installed in the passage for adsorbing evaporated gas, and a purge control valve installed in the passage for controlling a purge of said adsorbed evaporated gas from the canister to the intake pipe, said method comprising:

diagnosing existence of leakage in the purge system based on detecting pressure or pressure change in a part of the purge system at least including the fuel tank and the canister if said part of the purge system is hermetically sealed with said cap after introducing an air therein;

detecting a gear shift position of an automatic transmission;

determining whether said detected shift position is one of a neutral position and a parking position; and

stopping or canceling said leakage diagnosis when said detected shift position is one of said neutral position and said parking position.

14. A leakage diagnosing method for an evaporated gas purge system having a fuel tank with a removable cap, an intake pipe for an engine, a passage which connects the fuel tank to the intake pipe, a canister installed in the passage for adsorbing evaporated gas, and a purge control valve installed in the passage for controlling a purge of said adsorbed evaporated gas from the canister to the intake pipe, said method comprising:

tentatively determining existence of leakage in the purge system based on detecting pressure or pressure change in the purge system if the purge system is hermetically sealed with said cap after introducing a positive or negative pressure therein; and

performing a confirmatory further leakage diagnosis while an associated vehicle is running if it was earlier determined that leakage exists in the purge system while the vehicle was stopped before determining the probable existence of leakage thus likely eliminating the possibility that said cap was not in place when a leak was earlier detected.

15. A leakage diagnosing method as in claim 14, wherein:

negative pressure is introduced into the purge system while a vehicle is running if said negative pressure has earlier not been able to be introduced into the purge system while said vehicle was stopped before determining the probable existence of leakage thus likely eliminating the possibility that said cap was not in place when a leak was earlier detected.

16. A leakage diagnosing method as in claim 15 wherein:

introducing negative pressure into the fuel tank while a vehicle is running if negative pressure was earlier not able to be introduced into the fuel tank while said vehicle was stopped before determining the probable existence of leakage thus likely eliminating the possibility that said cap was not in place when a leak was earlier detected.