Apparatus and method for failure diagnosis of fuel vapor purge system

• US 6,848,298 B2
• Filed: 12/16/2002
• Issued: 02/01/2005
• Est. Priority Date: 01/11/2002
• Status: Expired due to Term

• Current Assignee: DENSO Corporation, Toyota Jidosha Kabushiki Kaisha (Toyota Motor Corporation)
• Original Assignee: DENSO Corporation, Toyota Jidosha Kabushiki Kaisha (Toyota Motor Corporation)
• Inventors: Ito, Tokiji, Hanai, Shuichi, Nagasaki, Kenji, Miyahara, Hideki, Ichikawa, Akira
• Primary Examiner(s): Garber, Charles D.
• Application Number:
  US10/319,685
• Publication Number:
  US 20030131655A1
• Time in Patent Office: 778 Days
• Field of Search: 73/40, 73/405.R, 73/497, 731/181, 123/518, 123/519, 123/520, 702/51
• US Class Current: 73/49.2
• CPC Class Codes: F02M 25/0818 having means for pressurising the evaporative emission space

Abstract

A fuel vapor purge system includes a fuel tank, a canister, and an evaporation route, and purges fuel vapor collected in the canister into an intake passage of an internal combustion engine. A failure diagnosis apparatus of the fuel vapor purge system includes a controller having a pressure difference applying unit for applying a pressure difference between the evaporation route and outside air. The controller also detects a level of an influence of the fuel vapor generated in the fuel tank on failure determination of the evaporation route, and detects both a pressure state obtained when the pressure difference applying unit communicates with a reference orifice communicating with the outside air and a pressure state obtained when the pressure difference applying unit communicates with the evaporation route. The failure diagnosis apparatus determines whether there is a failure in the evaporation route in view of the level of the influence by comparing the detected pressure states with each other.

Claims

1. A failure diagnosis apparatus of a fuel vapor purge system, the fuel vapor purge system including a fuel tank that stores fuel for an internal combustion engine, a canister that collects fuel vapor generated in the fuel tank, and an evaporation route that includes the fuel tank, the canister, an evaporation passage for introducing the fuel vapor generated in the fuel tank into the canister, and a purge passage for purging the fuel vapor collected in the canister into an intake passage of the internal combustion engine, the failure diagnosis apparatus comprising a controller that:

controls a pressure difference applying unit to applying a pressure difference between the evaporation route and outside air;

detects a level of an influence of the fuel vapor generated in the fuel tank on failure determination of the evaporation route;

detects both a pressure state obtained when the pressure difference applying unit communicates with a reference orifice communicating with the outside air and a pressure state obtained when the pressure difference applying unit communicates with the evaporation route;

determines whether there is a failure in the evaporation route in view of the level of the influence by comparing the former pressure state with the latter pressure; and

determines whether a leak occurs when a pressure introducing set period does not elapse after the pressure becomes stable, wherein when a pressure difference application time to the evaporation route reaches a predetermined time, the controller determines whether there is a failure in the evaporation route regardless of the determination result that the pressure change in the evaporation route becomes stable.

2. The failure diagnosis apparatus according to claim 1, further comprising a cut-off unit, controlled by the controller, for disconnecting the evaporation route from the outside air.

3. The failure diagnosis apparatus according to claim 2, further comprising:

a switch valve for selectively connecting a fresh-air introducing port of the canister to an atmosphere release port and the pressure difference applying unit; and

a bypass passage extending from the pressure difference applying unit to the fresh-air introducing port of the canister so as to bypass the switch valve, and having the reference orifice;

wherein the controller operates the pressure difference applying unit, switches the switch valve to the atmosphere release port, causes a pressure generated by the pressure difference applying unit to pass through the reference orifice of the bypass passage and the switch valve, then releases the pressure to the atmosphere from the atmosphere release port, and calculates the pressure thus released to the atmosphere as a reference value, operates the pressure difference applying unit, switches the switch valve to the pressure difference applying unit, causes a pressure generated by the pressure difference applying unit to pass through the switch valve, then supplies to the evaporation route from the fresh-air introducing port of the canister, and calculates the pressure thus supplied to the evaporation route as a comparative value, and determines whether there is a failure in the evaporation route by comparing the reference value with the comparative value.

4. The failure diagnosis apparatus according to claim 3, wherein the pressure difference applying unit is an electric air pump for supplying or sucking air.

5. The failure diagnosis apparatus according to claim 3, wherein the controller determines when a pressure change in the evaporation route becomes stable, based on a pressure change rate of the evaporation route, and determines a timing of determining whether there is a failure in the evaporation route based on the determination result that the pressure change in the evaporation route becomes stable.

6. The failure diagnosis apparatus according to claim 5, wherein when a pressure difference application time to the evaporation route is less than a predetermined time, the controller determines whether there is a failure in the evaporation route upon determining that the pressure change in the evaporation route becomes stable.

7. The failure diagnosis apparatus according to claim 3, further comprising a pressure sensor, coupled the controller, and the pressure sensor is provided between the pressure difference applying unit and the evaporation route.

8. The failure diagnosis apparatus according to claim 1, further comprising:

a switch valve for selectively connecting a fresh-air introducing port of the canister to an atmosphere release port and the pressure difference applying unit;

a bypass passage extending from the pressure difference applying unit to the fresh-air introducing port of the canister so as to bypass the switch valve, and having the reference orifice;

wherein the controller operates the pressure difference applying unit and switching the switch valve to the atmosphere release port, causes a pressure generated by the pressure difference applying unit to pass through the reference orifice of the bypass passage and the switch valve, then releases the pressure to the atmosphere from the atmosphere release port, and the pressure thus released to the atmosphere is calculated as a reference value, by operating the pressure difference applying unit and switching the switch valve to the pressure difference applying unit, a pressure generated by the pressure difference applying unit is caused to pass through the switch valve and is then supplied to the evaporation route from the fresh-air introducing port of the canister, and calculates the pressure thus supplied to the evaporation route as a comparative value; and

determines whether there is a failure in the evaporation route by comparing the reference value with the comparative value.

9. The failure diagnosis apparatus according to claim 1, wherein the controller determines that a pressure change in the evaporation route becomes stable, based on a pressure change rate of the evaporation route, and

determines a timing of determining whether there is a failure in the evaporation route based on the determination result that the pressure change in the evaporation route becomes stable.

10. The failure diagnosis apparatus according to claim 9, wherein when a pressure difference application time to the evaporation route is less than a predetermined time, the controller determines whether there is a failure in the evaporation route upon determining that the pressure change in the evaporation route becomes stable.

11. A failure diagnosis method of a fuel vapor purge system, the fuel vapor purge system including a fuel tank for storing fuel for an internal combustion engine, a canister for collecting fuel vapor generated in the fuel tank, and an evaporation route including the fuel tank, the canister, an evaporation passage for introducing the fuel vapor generated in the fuel tank into the canister, and a purge passage for purging the fuel vapor collected in the canister into an intake passage of the internal combustion engine, the method comprising the steps of:

detecting a level of an influence of the fuel vapor generated in the fuel tank on failure determination of the evaporation route;

detecting a pressure state obtained when a pressure difference applying unit for applying a pressure difference between the evaporation route and outside air communicates with a reference orifice communicating with the outside air;

detecting a pressure state obtained when the pressure difference applying unit communicates with the evaporation route; and

determining whether there is a failure in the evaporation route in view of the level of the influence by comparing the former pressure state with the latter pressure state;

determining whether a leak occurs when a pressure introducing set period does not elapse after the pressure becomes stable,

determining when a pressure difference application time to the evaporation route reaches a predetermined time; and

determining whether there is a failure in the evaporation route regardless of the determination result that the pressure change in the evaporation route becomes table.

12. The failure diagnosis method according to claim 11, further comprising the steps of:

operating the pressure difference applying unit;

switching a switch valve to an atmosphere release port so that a pressure generated by the pressure difference applying unit is caused to pass through the reference orifice of a bypass passage and the switch valve and is then released to atmosphere from the atmosphere release port;

calculating the pressure thus released to the atmosphere as a reference value, the bypass passage being a passage extending from the pressure difference applying unit to a fresh-air introducing port of the canister so as to bypass the switch valve, and having the reference orifice, and the switch valve being a valve for selectively connecting the fresh-air introducing port of the canister to the atmosphere release port and the pressure difference applying unit;

operating the pressure difference applying unit and switching the switch valve to the pressure difference applying unit so that a pressure generated by the pressure difference applying unit is caused to pass through the switch valve and is then supplied to the evaporation route from the fresh-air introducing port of the canister;

calculating the pressure thus supplied to the evaporation route as a comparative value; and

determining whether there is a failure in the evaporation route by comparing the reference value with the comparative value.

13. The failure diagnosis method according to claim 12, further comprising the steps of:

determining when a pressure change in the evaporation route becomes stable, based on a pressure change rate of the evaporation route; and

determining a timing of determining whether there is a failure in the evaporation route, based on the determination result that the pressure change in the evaporation route becomes stable.

14. The failure diagnosis method according to claim 11, further comprising the steps of:

determining when a pressure change in the evaporation route becomes stable, based on a pressure change rate of the evaporation route; and

determining a timing of determining whether there is a failure in the evaporation route, based on the determination result that the pressure change in the evaporation route becomes stable.

15. The failure diagnosis method according to claim 14, further comprising the steps of:

determining when a pressure difference application time to the evaporation route is less than a predetermined time; and

determining whether there is a failure in the evaporation route upon determining that the pressure change in the evaporation route becomes stable.