Fuel vapor control system with leak check

• US 6,832,509 B2
• Filed: 09/04/2002
• Issued: 12/21/2004
• Est. Priority Date: 09/04/2001
• Status: Expired

• Current Assignee: DENSO Corporation
• Original Assignee: DENSO Corporation
• Inventors: Miwa, Makoto, Maegawa, Yoshinori, Wakahara, Keiji, Morinaga, Syujiro
• Primary Examiner(s): Lefkowitz, Edward
• Assistant Examiner(s): DAVIS, OCTAVIA L
• Application Number:
  US10/233,595
• Publication Number:
  US 20030051540A1
• Time in Patent Office: 839 Days
• Field of Search: 73/40, 731/181, 73/497, 73/492, 123/520, 123/518, 123/698
• US Class Current: 73/114.39
• CPC Class Codes: F02M 25/0809 Judging failure of purge control system
• CPC Class Codes: F02M 25/0836 Arrangement of valves controlling the admission of fuel vapour to an engine, e.g. valve being disposed between fuel tank or absorption canister and intake manifold

Abstract

A fuel vapor control system has a controller that carries out a leak check processing after the engine is stopped. The controller includes a device that intermittently activates the controller itself or a part of the controller to sample an internal pressure of the fuel vapor passage. Then, after a predetermined time, the controller determines that whether the sampled values of the internal pressure indicate a leak or not by evaluating the sampled values. According to the arrangement, since at least a part of the controller is activated intermittently, the consumption of electricity can be reduced. The fuel vapor control system has a canister valve and a purge valve made of normally close type valves in order to reduce the consumption of electricity after the engine is stopped.

Claims

1. A fuel vapor control system for a fuel supply system of an engine, comprising:

means for detecting an internal pressure of a fuel vapor passage including a fuel tank;

means for closing the fuel vapor passage during a leak check period in which a leak check is carried out when the engine is not activated;

means, activated intermittently in the leak check period, for sampling the internal pressure intermittently in response to the activation so that the means for sampling consumes electrical power when activated to perform the sampling and does not consume electrical power when deactivated between sampling timings; and

means for determining a leak or not based on the sampled values of the internal pressure sampled by the sampling means.

2. The fuel vapor control system according to claim 1, wherein the sampling means is intermittently supplied the electrical power from a battery so that the battery supplies electrical power to the sampling means when the sampling means is activated and does not supply electrical power to the sampling means when the sampling means is deactivated.

3. The fuel vapor control system according to claim 1, wherein the determining means determines the leak or not based on a difference between a maximum pressure of the sampled values and a minimum pressure of the sampled values.

4. The fuel vapor control system according to claim 3, wherein the determining means determines the leak when the difference is smaller than a predetermined value.

5. The fuel vapor control system according to claim 1, wherein the determining means determines the leak or not based on a maximum pressure of the sampled values.

6. The fuel vapor control system according to claim 5, wherein the determining means determines the leak when the maximum pressure is smaller than a predetermined value.

7. The fuel vapor control system according to claim 1, wherein the determining means determines a leak or not based on an accumulated value of the sampled values.

8. The fuel vapor control system according to claim 7, wherein the accumulated value is calculated by accumulating absolute values of the sampled values.

9. The fuel vapor control system according to claim 1, wherein the closing means includes:

a normally close type valve which is capable of maintaining a closed condition without activation; and

a relief valve which defines an upper limit pressure in the fuel vapor passage.

10. The fuel vapor control system according to claim 1, further comprising:

a canister that adsorbs fuel vapor from the fuel tank, wherein the closing means includes;

a purge valve disposed between the canister and an intake passage of the engine, the purge valve being capable of maintaining a closed condition without activation; and

a canister valve disposed between the canister and the atmosphere, the canister valve being capable of maintaining a closed condition without activation.

11. The fuel vapor control system according to claim 1, wherein the sampling means varies a sampling interval in accordance with at least one of an elapsed time of the leak check, a changing rate of the internal pressure and a parameter correlating to the elapsed time or the changing rate.

12. The fuel vapor control system according to claim 11, wherein the sampling interval is set relatively shorter in a beginning of the leak check than that in an ending of the leak check.

13. The fuel vapor control system according to claim 1, further comprising means for determining a prohibition or permission of the leak check based on a parameter indicative of a condition of fuel vapor in the fuel tank.

14. The fuel vapor control system according to claim 13, wherein the parameter is a fuel temperature or a driving history of a vehicle that is indicative of the condition of fuel vapor in which the internal pressure clearly shows the leak or not.

18. The fuel vapor control system according to claim 1, wherein the sampling means is intermittently activated from an off condition, in which the power is not supplied, during the leak check period.

15. A fuel vapor control system for a fuel supply system of an engine, comprising:

a valve that closes a passage to define a closed chamber including a part of the fuel vapor passage;

a pressure sensor disposed on the closed chamber to detect an internal pressure of the closed chamber;

a controller that inputs a signal from the pressure sensor and operates the valve in a closed condition when a leak check is carried out when an engine is not activated, wherein

the controller includes;

a power control block that intermittently turns on power supply when the leak check is carried out;

a sampling block that is intermittently activated by being supplied power from the power control block and samples the internal pressure detected by the pressure sensor in response to an activation and that is deactivated by not being supplied power from the power control block between sampling timings; and

a leak check block that determines a leak or not based on values of the internal pressure sampled by the sampling block.

16. The fuel vapor control system according to claim 15, wherein the power control block intermittently turns on power of the controller, and

the valve is capable of maintaining a closed condition when the controller is not supplied power.

17. The fuel vapor control system according to claim 15, wherein the controller is activated from an off condition, in which the power is not supplied, when the leak check is carried out.

19. A method of controlling fuel vapor in a fuel supply system of an engine, the method comprising:

detecting an internal pressure of a fuel vapor passage including a fuel tank;

closing the fuel vapor passage during a leak check period in which a leak check is carried out when the engine is not activated;

sampling, using a sampling device, the internal pressure intermittently in response to intermittent activation of the sampling device during the leak check period so that the sampling device consumes electrical power when activated to perform the sampling and does not consume electrical power when deactivated between sampling timings; and

determining a leak or not based on the sampled values of the internal pressure sampled by the sampling device.

20. The method according to claim 19, wherein the sampling device is intermittently supplied the electrical power from a battery so that the battery supplies electrical power to the sampling device when the sampling device is activated and does not supply electrical power to the sampling device when the sampling device is deactivated.

21. The method according to claim 19, wherein determining the leak or not is based on a difference between a maximum pressure of the sampled values and a minimum pressure of the sampled values.

22. The method according to claim 21, wherein the determining comprises determining that the leak is present when the difference is smaller than a predetermined value.

23. The method according to claim 19, wherein determining the leak or not is based on a maximum pressure of the sampled values.

24. The method according to claim 23, wherein the determining comprises determining that the leak is present when the maximum pressure is smaller than a predetermined value.

25. The method according to claim 19, wherein determining the leak or not is based on an accumulated value of the sampled values.

26. The method according to claim 25, wherein the accumulated value is calculated by accumulating absolute values of the sampled values.

27. The method according to claim 19, wherein closing the fuel vapor passage is accomplished by a normally close type valve which is capable of maintaining a closed condition without activation, and a relief valve which defines an upper limit pressure in the fuel vapor passage.

28. The method according to claim 19, further comprising;

absorbing fuel vapor from the fuel tank in a canister, and

wherein closing the fuel vapor passage includes;

disposing a purge valve between the canister and an intake passage of the engine, the purge valve being capable of maintaining a closed condition without activation; and

disposing a canister valve between the canister and the atmosphere, the canister valve being capable of maintaining a closed condition without activation.

29. The method according to claim 19, wherein the sampling includes varying a sampling interval in accordance with at least one of an elapsed time of the leak check, a changing rate of the internal pressure and a parameter correlating to the elapsed time or the changing rate.

30. The method according to claim 29, wherein the sampling interval is set relatively shorter in a beginning of the leak check than that in an ending of the leak check.

31. The method according to claim 19, further comprising determining a prohibition or permission of the leak check based on a parameter indicative of a condition of fuel vapor in the fuel tank.

32. The method according to claim 31, wherein the parameter is a fuel temperature or a driving history of a vehicle that is indicative of the condition of fuel vapor in which the internal pressure clearly shows the leak or not.