Leak diagnosis system and leak diagnosis method

• US 7,472,582 B2
• Filed: 05/11/2006
• Issued: 01/06/2009
• Est. Priority Date: 05/12/2005
• Status: Expired due to Fees

• Current Assignee: DENSO Corporation
• Original Assignee: DENSO Corporation
• Inventors: Takano, Nobuhiro, Ito, Shinichi
• Primary Examiner(s): LARKIN, DANIEL SEAN
• Application Number:
  US11/431,651
• Publication Number:
  US 20060254342A1
• Time in Patent Office: 971 Days
• Field of Search: 73/492, 73/497
• US Class Current: 73/49.7
• CPC Class Codes: F02M 25/0809 Judging failure of purge control system

Abstract

An ECU drives a pump in a first stage at a first pumping capacity. The ECU drives the pump in a second stage after the first stage at a second pumping capacity, which is lower than the first pumping capacity. The second pumping capacity is set such that when at least one leak hole, which forms a predetermined total opening cross sectional area, exists in the purge apparatus, the driving of the pump at the second pumping capacity substantially maintains a predetermined reference pressure in the purge apparatus. The ECU diagnoses whether a leak hole exits in the purge apparatus based on the pressure measured with the pressure sensor in view of the predetermined reference pressure at the time of driving the pump in the second stage at the second pumping capacity.

Claims

1. A leak diagnosis system for a vehicle having an internal combustion engine, the leak diagnosis system comprising:

a fuel tank that receives fuel;

a purge apparatus that is communicated with the fuel tank and purges fuel gas, which is generated through vaporization of the fuel in the fuel tank, into an intake air pipe of the engine;

a pressure sensor that senses an internal pressure of the purge apparatus;

a pump that has an adjustable pump capacity and supplies a pressure to an interior of the purge apparatus;

a primary drive control means for driving the pump in a first stage at a first pumping capacity;

a secondary drive control means for driving the pump in a second stage after the first stage at a second pumping capacity, which is lower than the first pumping capacity, wherein the second pumping capacity is set such that when at least one leak hole, which forms a predetermined total opening cross sectional area, exists in the purge apparatus, the driving of the pump at the second pumping capacity by the secondary drive control means substantially maintains a predetermined reference pressure in the purge apparatus; and

a diagnosing means for diagnosing whether a leak hole exits in the purge apparatus based on the pressure measured with the pressure sensor in view of the predetermined reference pressure at the time of driving the pump in the second stage at the second pumping capacity by the secondary drive control means.

2. The leak diagnosis system according to claim 1, wherein the secondary drive control means starts driving the pump in the second stage when the pressure measured with the pressure sensor reaches a predetermined changeover pressure, which is between the predetermined reference pressure and an atmospheric pressure.

3. The leak diagnosis system according to claim 1, further comprising a fuel level sensor that measures a remaining fuel quantity in the fuel tank, wherein the primary drive control means drives the motor in the first stage for a predetermined operational time period, which is determined based on the remaining fuel quantity measured with the fuel sensor in view of prestored information that indicates a relationship between the remaining fuel quantity and the operational time period of the primary drive control means.

4. The leak diagnosis system according to claim 3, wherein when the remaining fuel quantity measured with the fuel level sensor is equal to or greater than a predetermined reference quantity, the primary drive control means is disabled, and the secondary drive control means is enabled to drive the pump in both of the first and second stages at the second pumping capacity.

5. The leak diagnosis system according to claim 4, wherein the predetermined reference quantity is equal to or greater than 90% of an internal volume of the fuel tank.

6. The leak diagnosis system according to claim 1, further comprising:

a vehicle battery that supplies electric power to the pump;

a battery charge level sensing means for measuring a remaining charge level of the battery;

the primary drive control means and the second drive control means are both enabled to drive the pump in the first and second stages, respectively, when the charge level measured with the battery charge level sensing means is equal to or greater than a primary control enabling value;

the primary drive control means is disabled when the charge level measured with the battery charge level sensing means is less than the primary control enabling value; and

the secondary drive control means is enabled to drive the pump in both of the first and second stages when the charge level measured with the battery charge level sensing means is less than the primary control enabling value but is equal to or greater than a secondary control enabling value, which is lower than the primary control enabling value.

7. The leak diagnosis system according to claim 1, wherein the pump is a single pump in the diagnosis system.

8. The leak diagnosis system according to claim 1, further comprising:

a changeover valve that is changeable between a first state and a second state, wherein;

in the first state, the changeover valve communicates between the purge apparatus and a surrounding atmosphere;

in the second state, the changeover valve communicates between the purge apparatus and the pump; and

a bypass passage that bypasses the changeover valve and always communicates between the purge apparatus and the pump.

9. The leak diagnosis system according to claim 8, further comprising a pressure setting means for variably setting at least one of the predetermined reference pressure and the changeover pressure when the pump is driven by the secondary drive control means at the second pumping capacity under the first state of the changeover valve.

10. The leak diagnosis system according to claim 9, wherein the pressure setting means sets the predetermined reference pressure when a change rate of the pressure measured with the pressure sensor becomes less that a predetermined rate.

11. The leak diagnosis system according to claim 1, wherein the pump is a vacuum pump that supplies a negative pressure to the interior of the purge apparatus.

12. The leak diagnosis system according to claim 1, further comprising:

at least one pressure related information sensor, each of which measures a corresponding pressure related information value, which changes in response to a pressure change in the purge apparatus; and

a primary stabilization determining means for determining whether the at least one pressure related information value measured with the at least one pressure related information sensor is substantially stabilized, wherein;

when the primary stabilization determining means determines that the at least one pressure related information value is not substantially stabilized, the primary drive control means and the secondary drive control means are both disabled in the first and second stages; and

when the primary stabilization determining means determines that the at least one pressure related information value is substantially stabilized, the primary drive control means and the secondary drive control means are enabled to drive the pump in the first and second stages, respectively.

13. The leak diagnosis system according to claim 12, wherein the at least one pressure related information value includes at least one of the internal pressure of the purge apparatus and a coolant temperature of engine coolant of the engine.

14. The leak diagnosis system according to claim 12, further comprising:

at least one of an intake air temperature sensor, which measures an intake air temperature of the engine, and an atmospheric pressure sensor, which measure an atmospheric pressure; and

a secondary stabilization determining means for determining whether the at least one of the intake air temperature and the atmospheric pressure is substantially stabilized, wherein the primary drive control means and the secondary drive control means are enabled to drive the pump in the first and second stages, respectively, upon satisfaction of all of the following conditions;

the primary stabilization determining means determines that the at least one pressure related information value is substantially stabilized; and

the secondary stabilization determining means determines that the at least one of the intake air temperature and the atmospheric pressure is substantially stabilized.

15. The leak diagnosis system according to claim 12, wherein the primary stabilization determining means determines whether the at least one pressure related information value is stabilized based on an amount of change in each of the at least one pressure related information value per unit time.

16. The leak diagnosis system according to claim 15, wherein the unit time is a predetermined fixed time period, which is previously determined.

17. The leak diagnosis system according to claim 15, wherein:

the unit time is a variable time period; and

the variable time period is shortened when a current determination result of the primary stabilization determining means indicates that the amount of change in each of the at least one pressure related information value per unit time is reduced in comparison to the amount of change in each of the at least one pressure related information value per unit time in a previous determination result of the primary stabilization determining means.

18. The leak diagnosis system according to claim 15, wherein:

the at least one pressure related information sensor includes a coolant temperature sensor, which measures a coolant temperature of engine coolant of the engine;

the primary stabilization determining means determines an initial stabilization determining time point based on an initial value of the coolant temperature, which is measured first time with the coolant temperature sensor after turning off the engine in view of prestored information that indicates a relationship between the coolant temperature and the initial stabilization determining time point; and

the relationship between the coolant temperature and the initial stabilization determining time point is set such that when the coolant temperature becomes higher, the initial stabilization determining time point is further delayed.

19. The leak diagnosis system according to claim 12, further comprising a storage means for storing a stabilizing time period from a time of turning off the engine to a time of determining that the at least one pressure related information value is substantially stabilized by the primary stabilization determining means, wherein the primary stabilization determining means adjusts the initial stabilization determining time point based on the stabilizing time period stored in the storage means.

20. The leak diagnosis system according to claim 12, wherein:

the primary stabilization determining means determines that the at least one pressure related information value is substantially stabilized when a stabilizing time period is elapsed since a time of turning off of the engine; and

the primary stabilization determining means determines the stabilizing time period based on;

a relationship between an initial value of each of the at least one pressure related information value after turning off of the engine and the stabilizing time period of the corresponding pressure related information value; and

an actual measured value of each of the at least one pressure related information value, which is measured with a corresponding one of the at least one pressure related information sensor right after turning off of the engine.

21. A leak diagnosis system for a vehicle having an internal combustion engine, the leak diagnosis system comprising:

a fuel tank that receives fuel;

a purge apparatus that is communicated with the fuel tank and purges fuel gas, which is generated through vaporization of the fuel in the fuel tank, into an intake air pipe of the engine;

a pressure sensor that senses an internal pressure of the purge apparatus;

a pump that has an adjustable pump capacity and supplies a pressure to an interior of the purge apparatus; and

a controller that controls the pump and diagnoses whether a leak hole exists in the purge apparatus, wherein;

the controller drives the pump in a first stage at a first pumping capacity;

the controller drives the pump in a second stage after the first stage at a second pumping capacity, which is lower than the first pumping capacity, wherein the second pumping capacity is set such that when at least one leak hole, which forms a predetermined total opening cross sectional area, exists in the purge apparatus, the driving of the pump at the second pumping capacity substantially maintains a predetermined reference pressure in the purge apparatus; and

the controller diagnoses whether a leak hole exits in the purge apparatus based on the pressure measured with the pressure sensor in view of the predetermined reference pressure at the time of driving the pump in the second stage at the second pumping capacity.

22. A leak diagnosis method comprising:

driving a pump in a first stage at a first pumping capacity, wherein the pump supplies a pressure to an interior of a purge apparatus that is communicated with a fuel tank of a vehicle and purges fuel gas, which is generated through vaporization of fuel in the fuel tank, into an intake air pipe of an internal combustion engine of the vehicle;

driving the pump in a second stage after the first stage at a second pumping capacity, which is lower than the first pumping capacity, wherein the second pumping capacity is set such that when at least one leak hole, which forms a predetermined total opening cross sectional area, exists in the purge apparatus, the driving of the pump at the second pumping capacity substantially maintains a predetermined reference pressure in the purge apparatus; and

diagnosing whether a leak hole exits in the purge apparatus based on an internal pressure of the purge apparatus measured with a pressure sensor in view of the predetermined reference pressure at the time of driving the pump in the second stage at the second pumping capacity.

23. The leak diagnosis method according to claim 22, wherein the driving of the pump in the second stage includes starting the driving of the pump in the second stage when the internal pressure of the purge apparatus measured with the pressure sensor reaches a predetermined changeover pressure, which is between the predetermined reference pressure and an atmospheric pressure.

24. The leak diagnosis method according to claim 22, wherein the driving of the pump in the first stage includes driving the motor in the first stage for a predetermined operational time period, which is determined based on a remaining fuel quantity in the fuel tank measured with a fuel sensor in view of prestored information that indicates a relationship between the remaining fuel quantity and the operational time period of the first stage.

25. The leak diagnosis method according to claim 22, further comprising:

enabling both of the driving of the pump in the first stage at the first pumping capacity and the driving of the pump in the second stage at the second pumping capacity when a charge level of a vehicle battery is equal to or greater than a primary control enabling value and is thereby enables driving of the pump by electric power supplied from the battery;

disabling the driving of the pump at the first pumping capacity when the charge level of the battery is less than the primary control enabling value; and

enabling the driving of the pump at the second pumping capacity in both of the first and second stages when the charge level of the battery is less than the primary control enabling value but is equal to or greater than a secondary control enabling value, which is lower than the primary control enabling value.

26. The leak diagnosis method according to claim 22, further comprising disabling the driving of the pump in the first stage at the first pumping capacity and the driving of the pump in the second stage at the second pumping capacity when it is determined that at least one pressure related information value, which changes in response to a pressure change in the purge apparatus, is not substantially stabilized.