Evaporative fuel-processing system for internal combustion engines

• US 5,299,545 A
• Filed: 09/10/1992
• Issued: 04/05/1994
• Est. Priority Date: 09/13/1991
• Status: Expired

• Current Assignee: Honda Giken Kogyo Kabushiki Kaisha (Honda Motor Company)
• Original Assignee: Honda Giken Kogyo Kabushiki Kaisha (Honda Motor Company)
• Inventors: Maruyama, Hiroshi, Suzuki, Takeshi, Yamanaka, Masayoshi, Kuroda, Shigetaka, Sawamura, Kazutomo, Nemoto, Shoichi, Chikamatsu, Masataka
• Primary Examiner(s): MILLER, CARL STUART
• Application Number:
  US07/942,875
• Time in Patent Office: 572 Days
• Field of Search: 123/198 D, 123/520, 123/519, 123/518, 123/516, 123/521
• US Class Current: 123/520
• CPC Class Codes: F02D 2041/225 Leakage detection
• CPC Class Codes: F02D 2200/0406 Intake manifold pressure
• CPC Class Codes: F02D 2200/0414 Air temperature
• CPC Class Codes: F02D 2200/0606 Fuel temperature
• CPC Class Codes: F02D 2200/703 Atmospheric pressure
• CPC Class Codes: F02D 41/003 Adding fuel vapours, e.g. drawn from engine fuel reservoir
• CPC Class Codes: F02D 41/1454 the characteristics being an oxygen content or concentration or the air-fuel ratio
• CPC Class Codes: F02M 2025/0845 Electromagnetic valves
• CPC Class Codes: F02M 25/0809 Judging failure of purge control system

Abstract

An evaporative fuel processing system adapted to be capable of detecting abnormality of an evaporative emission control system for storing, in a canister, evaporative fuel generated from a fuel tank for holding fuel to be supplied to an internal combustion engine, and purging evaporative fuel into the intake system of the engine. A first control valve is arranged across a passage extending between the fuel tank and the canister. A second control valve is arranged across a passage extending between the canister and the intake system of the engine. A third control valve is provided for an air inlet port of the canister communicatable with the atmosphere. Through operating these control valves to open and close them, the evaporative emission control system is negatively pressurized, and abnormality of this system is detected based on the pressure detected in this negatively pressurized state thereof. Timing for carrying out abnormality determination is determined depending on conditions of the fuel tank. Before starting the whole process for abnormality diagnosis of the system, evaporative fuel stored in the canister is allowed to be purged for a predetermined time period. When the temperature of fuel in the fuel tank exceeds a predetermined value, the abnormality determination is inhibited.

Claims

1. An evaporative fuel-processing system for an internal combustion engine having an intake system, including an evaporative emission control system having a fuel tank, a canister containing an adsorbent, said canister having an air inlet port communicatable with the atmosphere, an evaporative fuel-guiding passage extending between said canister and said fuel tank, a first control valve arranged across said evaporative fuel-guiding passage, an evaporative fuel-purging passage extending between said canister and said intake system, and a second control valve arranged across said evaporative fuel-purging passage,

said evaporative fuel-processing system having an abnormality-determining system which comprises:

pressure-detecting means for detecting pressure within said evaporative emission control system;

negatively-pressurizing means for negatively pressurizing said evaporative emission control system; and

abnormality-determining means for determining abnormality of said evaporative emission control system based on the pressure within said fuel tank detected after said evaporative emission control system has been negatively pressurized by said negatively-pressurizing means.

2. An evaporative fuel-processing system according to claim 1, wherein said abnormality-determining means determines the abnormality of said evaporative emission control system based on a rate of change in the pressure within said fuel tank occurring before said evaporative emission control system is set to a predetermined negatively-pressurized condition by said negatively-pressurizing means and a rate of change in the pressure within said fuel tank occurring after said predetermined negatively-pressurized condition of said evaporative emission control system has been established.

3. An evaporative fuel-processing system according to claim 1, including tank condition-detecting means for detecting conditions of said fuel tank, wherein said abnormality-determining means carries out abnormality determination when a predetermined time period has elapsed after said evaporative emission control system was negatively pressurized, said predetermined time period being corrected by a correcting time period set in response to said conditions of said fuel tank detected by said tank condition-detecting means.

4. An evaporative fuel-processing system according to claim 2, including tank condition-detecting means for detecting conditions of said fuel tank, wherein said abnormality-determining means carries out abnormality determination when a predetermined time period has elapsed after said evaporative emission control system was negatively pressurized, said predetermined time period being corrected by a correcting time period set in response to said conditions of said fuel tank detected by said tank condition-detecting means.

5. An evaporative fuel-processing system according to claim 1, wherein said abnormality-determining means determines abnormality of said evaporative emission control system by comparing a value of a parameter indicative a rate of change in the pressure within said fuel tank detected after said evaporative emission control system has been negatively pressurized by said negatively-pressurizing means with a predetermined reference value, said predetermined reference value being determined according to a time period required for setting said evaporative emission control system to said predetermined negatively-pressurized condition by said negatively-pressurizing means.

6. An evaporative fuel-processing system according to claim 1, including means for purging evaporative fuel stored in said canister for a predetermined time period before the abnormality-determining process is started by said abnormality-determining system.

7. An evaporative fuel-processing system according to claim 1, including fuel temperature-detecting means for detecting the temperature of fuel contained in said fuel tank, and determination-inhibiting means for inhibiting execution of abnormality-determining process by said abnormality-determining system when said fuel temperature detected exceeds a predetermined value.

8. An evaporative fuel-processing system for an internal combustion engine having an intake system, including an evaporative emission control system having a fuel tank, a canister containing an adsorbent, said canister having an air inlet port communicatable with the atmosphere, an evaporative fuel-guiding passage extending between said canister and said fuel tank, a first control valve arranged across said evaporative fuel-guiding passage, an evaporative fuel-purging passage extending between said canister and said intake system, and a second control valve arranged across said evaporative fuel-purging passage,

said evaporative fuel-processing system having an abnormality-determining system which comprises:

engine operating condition-detecting means for detecting operating conditions of said engine;

a third control valve for effecting and cutting off the communication of said air inlet port of said canister with the atmosphere;

tank internal pressure-detecting means for detecting pressure within said fuel tank;

negatively-pressurizing means for setting said evaporative emission control system to a predetermined negatively-pressurized condition by controlling said first to third control valves when it is detected by said said engine operating condition-detecting means that said engine is in operation;

a first rate of change-detecting means for detecting a rate of change in the pressure within said fuel tank caused by controlling opening and closing of said first control valve;

a second rate of change-detecting means for detecting a rate of change in the pressure within said fuel tank caused by closing said second control valve after said negatively-pressurized condition of said evaporative emission control system has been established; and

abnormality-determining means for determining abnormality of said evaporative emission control system based on results of detection by said first and second rate of change-detecting means.

9. An evaporative fuel-processing system according to claim 8, including tank condition-detecting means for detecting conditions of said fuel tank, wherein said abnormality-determining means carries out abnormality determination when a predetermined time period has elapsed after said evaporative emission control system was negatively pressurized, said predetermined time period being corrected by a correcting time period set in response to said conditions of said fuel tank detected by said tank condition-detecting means.

10. An evaporative fuel-processing system according to claim 8, wherein said abnormality-determining means determines abnormality of said evaporative emission control system by comparing a value of a parameter indicative of a rate of change in the pressure within the said fuel tank detected after said evaporative emission control system has been negatively pressurized by said negatively-pressurizing means with a predetermined reference value during the negatively pressurizing, said predetermined reference value being determined according to a time period required for setting said evaporative emission control system to said predetermined negatively-pressurized condition by said negatively-pressurizing means.

11. An evaporative fuel-processing system according to claim 9, wherein said abnormality-determining means determines abnormality of said evaporative emission control system by comparing a value of a parameter indicative of a rate of change in the pressure within the said fuel tank detected after said evaporative emission control system has been negatively pressurized by said negatively-pressurizing means with a predetermined reference value during the negatively pressurizing, said predetermined reference value being determined according to a time period required for setting said evaporative emission control system to said predetermined negatively-pressurized condition by said negatively-pressurizing means.

12. An evaporative fuel-processing system according to claim 8, wherein said abnormality-determining system includes fuel amount-detecting means for detecting an amount of fuel contained in said fuel tank, said abnormality-determining means determines the abnormality of said evaporative emission control system based on results of detection by said first and second rate of change-detecting means and said fuel amount-detecting means.

13. An evaporative fuel-processing system according to claim 8, including means for purging evaporative fuel stored in said canister for a predetermined time period before the abnormality-determining process is started by said abnormality-determining system.

14. An evaporative fuel-processing system according to claim 8, including fuel temperature-detecting means for detecting the temperature of fuel contained in said fuel tank, and determination-inhibiting means for inhibiting execution of abnormality-determining process by said abnormality-determining system when said fuel temperature detected exceeds a predetermined value.

15. An evaporative fuel-processing system for an internal combustion engine having an intake system, including an evaporative emission control system having a fuel tank, a canister containing an adsorbent, said canister having an air inlet port communicatable with the atmosphere, an evaporative fuel-guiding passage extending between said canister and said fuel tank, a first control valve arranged across said evaporative fuel-guiding passage, an evaporative fuel-purging passage extending between said canister and said intake system, and a second control valve arranged across said evaporative fuel-purging passage,

said evaporative fuel-processing system having an abnormality-determining system which comprises:

engine operating condition-detecting means for detecting operating conditions of said engine;

a third control valve for effecting and cutting off the communication of said air inlet port of said canister with the atmosphere;

tank internal pressure-detecting means for detecting pressure within said fuel tank;

negatively-pressurizing means for setting said evaporative emission control system to a predetermined negatively-pressurized condition by controlling said first to third control valves when it is detected by said said engine operating condition-detecting means that said engine is in operation; and

abnormality-determining means for effecting a determination as to whether or not said evaporative emission control system is abnormally functioning, when a predetermined time period has elapsed during the negatively-pressurizing process by said negatively-pressurizing means.

16. An evaporative fuel-processing system according to claim 15, wherein said abnormality-determining system includes evaporative fuel generation rate-detecting means for detecting a parameter of an amount of evaporative fuel generated per unit time within said fuel tank, said abnormality-determining means determining that said evaporative emission control system is abnormal on condition that said parameter indicative of said amount of evaporative fuel generated per unit time within said fuel tank is smaller than a predetermined value.

17. An evaporative fuel-processing system according to claim 15, including means for purging evaporative fuel stored in said canister for a predetermined time period before the abnormality-determining process is started by said abnormality-determining system.

18. An evaporative fuel-processing system according to claim 15, including fuel temperature-detecting means for detecting the temperature of fuel contained in said fuel tank, and determination-inhibiting means for inhibiting execution of abnormality-determining process by said abnormality-determining system when said fuel temperature detected exceeds a predetermined value.

19. An evaporative fuel-processing system for an internal combustion engine having an intake system, including an evaporative emission control system having a fuel tank, a canister containing an adsorbent, said canister having an air inlet port communicatable with the atmosphere, an evaporative fuel-guiding passage extending between said canister and said fuel tank, an evaporative fuel-purging passage extending between said canister and said intake system, and a purge control valve arranged across said evaporative fuel-purging passage,

said evaporative emission control system comprising:

a drain shut valve disposed to establish and shut off communication between said air inlet port of said canister and the atmosphere;

pressure-detecting means for detecting pressure within said evaporative emission control system;

negatively-pressurizing means for negatively pressurizing said evaporative emission control system; and

abnormality-determining means for determining abnormality of said evaporative emission control system based on an extent to which the pressure is maintained within said evaporative emission control system, said extent being detected based on the pressure within said evaporative emission control system detected by said pressure-detecting means, after said evaporative emission control system has been negatively pressured by said negatively-pressurizing means.

20. An evaporative fuel-processing system according to claim 19, wherein said abnormality-determining means includes pressure-holding means for holding the pressure within said evaporative emission control system after said evaporative emission control system has been negatively pressurized by said negatively-pressurizing means, said abnormality-determining means detecting the extent to which the pressure is maintained within said evaporative emission control system based on the pressure within said evaporative emission control system detected by said pressure-detecting means, while the pressure within said evaporative emission control system is held by said pressure-holding means.

21. An evaporative fuel-processing system according to claim 20, wherein said negatively-pressurizing means opens said purge control valve and at the same time closes said drain shut valve to negatively pressurize said evaporative emission control system, and said pressure-holding means closes said purge control valve and at the same time closes said drain shut valve to hold the pressure within said evaporative emission control valve.

22. An evaporative fuel-processing system according to claim 20, wherein said abnormality-determining means determines the extent to which the pressure is maintained within said evaporative emission control means, by detecting a change in the pressure within said evaporative emission control system detected by said pressure-detecting means over a predetermined time period, and determines that there is an abnormality in said evaporative emission control system, when the detected change exceeds a predetermined value.