Internal-combustion engines – Charge forming device – Having fuel vapor recovery and storage system
Reissue Patent
1996-03-22
2002-10-29
Miller, Carl S. (Department: 3747)
Internal-combustion engines
Charge forming device
Having fuel vapor recovery and storage system
C123S1980DA
Reissue Patent
active
RE037895
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to an evaporative fuel-processing system for internal combustion engines, and more particularly to an evaporative fuel-processing system for internal combustion engines, which is capable of performing abnormality diagnosis of an evaporative emission control system for purging evaporative fuel generated from a fuel tank of the engine into an intake system of same.
2. Prior Art
Conventionally, there has been widely used an evaporative fuel-processing system for internal combustion engines, which comprises a fuel tank, a canister having an air inlet port provided therein, a first control valve arranged across an evaporative fuel-guiding passage extending from the fuel tank to the canister, and a second control valve arranged across a purging passage extending from the canister to the intake system of the engine.
A system of this kind temporarily stores evaporative fuel in the canister, which is then purged into the intake system of the engine.
Whether a system of this kind is normally operating can be checked, for example, by comparing a first value of an air-fuel ratio correction coefficient assumed when purging of evaporative fuel into the intake system is stopped and a second value of the air-fuel ratio correction coefficient assumed when purging of evaporative fuel is effected, after completion of warming-up of the engine. That is, when the evaporative fuel-processing system is normally functioning to purge evaporative fuel into the intake system, an air-fuel mixture supplied to the engine is enriched by the evaporative fuel purged. The enriched air-fuel mixture is detected by an air-fuel ratio sensor, e.g. an O
2
sensor, and hence the air-fuel ratio correction coefficient calculated for feedback control of the air-fuel ratio assumes a smaller value. Therefore, monitoring of the manner of decrease in the air-fuel ratio correction coefficient enables to determine abnormality of the evaporative fuel-processing system. This abnormality diagnosis method is disclosed in U.S. Pat. No. 5,085,194.
However, the above abnormality diagnosis method using the air-fuel ratio correction coefficient suffers from a problem that in the case where a leak of evaporative fuel occurs from defective seals provided at piping connections, valves, the fuel tank, etc. of the system, (e.g. a seal at a filler cap of the fuel tank), it is impossible to detect the leak by the above method, which can result in emission of a large amount of evaporative fuel into the air.
SUMMARY OF THE INVENTION
It is the object of the invention to provide an evaporative fuel-processing system for an internal combustion engine, which is capable of detecting abnormality of an evaporative emission control system, by detecting whether there occurs a leak of evaporative fuel from seals provided at piping connections, etc. of the system.
To attain the above object, according to a first aspect of the invention, there is provided 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, the canister having an air inlet port communicatable with the atmosphere, an evaporative fuel-guiding passage extending between the canister and the fuel tank, a first control valve arranged across the evaporative fuel-guiding passage, an evaporative fuel-purging passage extending between the canister and the intake system, and a second control valve arranged across the evaporative fuel-purging passage.
The evaporative fuel-processing system according to the first aspect of the invention is characterized by having an abnormality-determining system which comprises:
tank internal pressure-detecting means for detecting pressure within the fuel tank;
negatively-pressurizing means for negatively pressurizing the evaporative emission control system; and
abnormality-determining means for determining abnormality of the evaporative emission control system based on the pressure within the fuel tank detected after the evaporative emission control system has been negatively pressurized by the negatively-pressuring means.
Preferably, the abnormality-determining means determines the abnormality of the evaporative emission control system based on a rate of change in the pressure within the fuel tank occurring before the evaporative emission control system is set to a predetermined negatively-pressurized condition by the negatively-pressurizing means and a rate of change in the pressure within the fuel tank occurring after the predetermined negatively-pressurized condition of the evaporative emission control system has been established.
Preferably, the evaporative fuel-processing system includes tank condition-detecting means for detecting conditions of the fuel tank, wherein the abnormality-determining means carries out abnormality determination when a predetermined time period has elapsed after the evaporative emission control system was negatively pressurized the predetermined time period being corrected by a correcting time period set in response to the conditions of the fuel tank detected by the tank condition-detecting means.
Preferably, the abnormality-determining means determines abnormality of the evaporative emission control system by comparing a value of a parameter indicative a rate of change in the pressure within the fuel tank detected after the evaporative emission control system has been negatively pressurized by the negatively-pressurizing means with a predetermined reference value, the predetermined reference value being determined according to a time period required for setting the evaporative emission control system to the predetermined negatively-pressurized condition by the negatively-pressurizing means.
Preferably, the evaporative fuel-processing system includes means for purging evaporative fuel stored in the canister for a predetermined time period before the abnormality-determining process is started by the abnormality-determining system.
Preferably, the evaporative fuel-processing system includes fuel temperature-detecting means for detecting the temperature of fuel contained in the fuel tank, and determination-inhibiting means for inhibiting execution of abnormality-determining process by the abnormality-determining system when the fuel temperature detected exceeds a predetermined value.
According to a second aspect of the invention, the evaporative fuel-processing system is characterized by having an abnormality-determining system which comprises:
engine operating condition-detecting means for detecting operating conditions of the engine;
a third control valve for effecting and cutting off the communication of the air inlet port of the canister with the atmosphere;
tank internal pressure-detecting means for detecting pressure within the fuel tank;
negatively-pressurizing means for setting the evaporative emission control system to a predetermined negatively-pressurized condition by controlling the first to third control valves when it is detected by the the engine operating condition-detecting means that the engine is in operation;
a first rate of change-detecting means for detecting a rate of change in the pressure within the fuel tank caused by controlling opening and closing of the first control valve;
a second rate of change-detecting means for detecting a rate of change in the pressure within the fuel tank caused by closing the second control valve after the negatively-pressurized condition of the evaporative emission control system has been established; and
abnormality-determining means for determining abnormality of the evaporative emission control system based on results of detection by the first and second rate of change-detecting means.
Preferably, the evaporative fuel-processing system of the second aspect of the invention also includes tank condition-detecting means for detecting conditions of the fuel tank, wherein the abnormality-determining means carries out abnormality determination when a predetermined
Chikamatsu Masataka
Kuroda Shigetaka
Maruyama Hiroshi
Nemoto Shoichi
Sawamura Kazutomo
Arent Fox Kintner & Plotkin & Kahn, PLLC
Honda Giken Kogyo Kabushiki Kaisha
Miller Carl S.
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