Evaporative fuel processing apparatus and control method of same

• US 6,761,154 B2
• Filed: 05/29/2003
• Issued: 07/13/2004
• Est. Priority Date: 06/07/2002
• Status: Expired due to Term

• Current Assignee: Toyota Jidosha Kabushiki Kaisha (Toyota Motor Corporation)
• Original Assignee: Toyota Jidosha Kabushiki Kaisha (Toyota Motor Corporation)
• Inventors: Takagi, Naoya, Hyodo, Yoshihiko
• Primary Examiner(s): MOHANTY, BIBHU R
• Application Number:
  US10/446,820
• Publication Number:
  US 20030226549A1
• Time in Patent Office: 411 Days
• Field of Search: 123/520, 123/519, 123/518, 123/198.D, 731/181
• US Class Current: 123/520
• CPC Class Codes: F02M 25/0818 having means for pressurising the evaporative emission space

Abstract

In an evaporative fuel processing apparatus, a fuel tank and a canister communicate with each other through a vapor passage, and an intake passage of an internal combustion engine and the canister communicates with each other through a purge passage. The evaporative fuel processing apparatus includes an open/close valve which opens or closes the vapor passage, a switching valve which makes the canister open to the atmosphere or isolates the canister from the atmosphere, a booster pump capable of applying pressure to the canister while the switching valve isolates the canister from the atmosphere, a purge control valve which opens or closes the purge passage, and an ECU which controls the open/close valve, the switching valve, the booster pump and the purge control valve.

Claims

1. An evaporative fuel processing apparatus comprising:

a fuel tank;

a canister which communicates with the fuel tank through a vapor passage;

a purge passage which allows an intake passage of an internal combustion engine and the canister to communicate with each other;

an open/close valve which opens or closes the vapor passage;

an isolated state switching mechanism which makes the canister open to an atmosphere or isolates the canister from the atmosphere;

a pressure adjusting mechanism which increases or decreases a pressure in the canister;

a purge control valve which opens or closes the purge passage; and

a control system which controls the open/close valve, the isolated state switching mechanism, the pressure adjusting mechanism and the purge control valve.

2. The evaporative fuel processing apparatus according to claim 1, wherein the control system

closes a canister space which includes the canister and does not include the fuel tank by closing the open/close valve, isolating the canister from the atmosphere using the isolated state switching mechanism, and closing the purge control valve;

adjusts an internal pressure in the closed canister space using the pressure adjusting mechanism; and

performs a diagnosis on leakage in the canister space based on the adjusted internal pressure in the canister space.

3. The evaporative fuel processing apparatus according to claim 2, wherein, the control system prohibits opening of the open/close valve when it is determined that there is leakage in the canister space.

4. The evaporative fuel processing apparatus according to claim 2, wherein the control system

closes an entire space including both of the canister and the fuel tank as a single space by opening the open/close valve, isolating the canister from the atmosphere using the isolated state switching mechanism, and closing the purge control valve, when it is determined that there is no leakage in the canister space;

adjusts an internal pressure in the closed entire space using the pressure adjusting mechanism; and

performs a diagnosis on leakage in the entire space based on the adjusted internal pressure in the entire space.

5. The evaporative fuel processing apparatus according to claim 2, wherein the control system

closes an entire space including both of the canister and the fuel tank as a single space by opening the open/close valve, isolating the canister from the atmosphere using the isolated state switching mechanism, and closing the purge control valve after a completion of a leakage diagnosis for the canister space;

adjusts an internal pressure in the closed entire space using the pressure adjusting mechanism; and

performs a diagnosis on leakage in the entire space based on the adjusted internal pressure in the entire space.

6. The evaporative fuel processing apparatus according to claim 5, wherein the control system

stores a pressure which the internal pressure in the canister space has reached in a process of a leakage diagnosis as an abnormal time pressure when it is determined that there is leakage in the canister space;

and

sets a reference value used in a leakage diagnosis for the entire space based on the abnormal time pressure, and

performs a leakage diagnosis for the entire space based on the set reference value when it is determined that there is leakage in the canister space.

7. The evaporative fuel processing apparatus according to claim 1, wherein the control system

detects an internal pressure in the fuel tank when the open/close valve is kept closed;

and

performs a leakage diagnosis for the fuel tank based on the closed time tank internal pressure.

8. The evaporative fuel processing apparatus according to claim 1, wherein the control system

closes the open/close valve when an internal combustion engine is stopped;

openes the open/close valve when it becomes necessary to allow the fuel tank and the canister to communicate with each other while the internal combustion engine is stopped; and

closes the open/close valve when it becomes unnecessary to allow the fuel tank and the canister to communicate with each other while the internal combustion engine is stopped, after the open/close valve is opened.

9. The evaporative fuel processing apparatus according to claim 8, wherein when it becomes necessary to allow the fuel tank and the canister to communicate with each other is when the leakage diagnosis is performed.

10. The evaporative fuel processing apparatus according to claim 1, wherein the control system

allows purge gas to flow from the canister to the intake passage by making the canister open to the atmosphere using the isolated state switching mechanism, and opening the purge control valve during operation of an internal combustion engine;

detects concentration of the purge gas while the purge gas flows; and

allows the purge gas to flow while the open/close valve is kept closed, and detects concentration of purge gas generated at this time as closed time concentration.

11. The evaporative fuel processing apparatus according to claim 1, wherein, the control system

allows purge gas to flow from the canister to the intake passage by making the canister open to the atmosphere using the isolated state switching mechanism, and opening the purge control valve during operation of an internal combustion engine;

detects concentration of the purge gas while the purge gas flows; and

maintains the open/close valve in a closed state while the concentration of the purge gas is equal to or higher than predetermined concentration.

12. The evaporative fuel processing means according to claim 1, wherein the control system

controls the isolated state switching mechanism such that the canister is isolated from the atmosphere when an internal pressure in the canister exceeds a predetermined reference value which is higher than the atmospheric pressure.

13. The evaporative fuel processing apparatus according to claim 12, wherein the control system controls the isolated state switching mechanism such the canister is isolated from the atmosphere after the internal pressure in the canister is increased by the pressure adjusting mechanism at least until the internal pressure decreases to a value equal to or lower than the predetermined reference value.

14. The evaporative fuel processing apparatus according to claim 1, wherein the control system includes a pressure sensor capable of selectively measuring an internal pressure in the canister which is made to be open to the atmosphere by the isolated state switching mechanism and an internal pressure in the canister which is isolated from the atmosphere by the isolated state switching mechanism.

15. The evaporative fuel processing apparatus according to claim 14, wherein the control system includes detection pressure switching mechanism for selectively introducing the internal pressure in the canister and an internal pressure in the fuel tank to a space whose pressure is detected by the pressure sensor.

16. The evaporative fuel processing apparatus according to claim 14, wherein the control system

forms a first state in which an atmospheric pressure is introduced to a space whose pressure is detected by the pressure sensor;

forms a second state in which a fluctuating pressure is introduced to the space whose pressure is detected by the pressure sensor; and

determines that the pressure sensor is in a normal state when a change in an output from the pressure sensor in the first state is smaller than a first reference value and a change in an output from the pressure sensor in the second state is larger than a second reference value.

17. A control method of an evaporative fuel processing apparatus comprising a fuel tank, a canister which communicates with the fuel tank through a vapor passage, a purge passage which allows an intake passage of an internal combustion engine and the canister to communicate with each other, an isolated state switching mechanism which makes the canister open to an atmosphere or which isolates the canister from the atmosphere, and a purge control valve which opens or closes the purge passage, comprising the steps of:

closing the canister space which includes the canister and which does not include the fuel tank by closing an open/close valve provided in the vapor passage, isolating the canister from the atmosphere using the isolated state switching mechanism, and closing the purge control valve;

adjusting an internal pressure in the closed canister space to increase or decrease; and

performing a leakage diagnosis based on the internal pressure in the canister space adjusted by the canister space internal pressure adjusting mechanism.

18. The evaporative fuel processing method according to claim 17, further comprising by further comprising the step of:

prohibiting opening of the open/close valve when it is determined that there is leakage in the canister space.

19. The evaporative fuel processing method according to claim 17, characterized by further comprising the steps of

closing an entire space including both of the canister and the fuel tank as a single space by opening the open/close valve, isolating the canister from the atmosphere using the isolated state switching mechanism, and closing the purge control valve, when it is determined that there is no leakage in the canister space;

adjusting an internal pressure in the closed entire space to increase or decrease; and

performing a diagnosis on leakage in the entire space based on the adjusted internal pressure in the entire space.

20. The evaporative fuel processing method according to claim 17, characterized by further comprising the steps of:

closing an entire space including both of the canister and the fuel tank as a single space by opening the open/close valve, isolating the canister from the atmosphere using the isolated state switching mechanism, and closing the purge control valve after a completion of a leakage diagnosis for the canister space;

adjusting an internal pressure in the closed entire space to increase or decrease; and

performing a diagnosis on leakage in the entire space based on the adjusted internal pressure in the entire space.