Internal-combustion engines – Charge forming device – Having fuel vapor recovery and storage system
Reexamination Certificate
2003-03-31
2004-08-10
Moulis, Thomas N. (Department: 3747)
Internal-combustion engines
Charge forming device
Having fuel vapor recovery and storage system
C123S520000
Reexamination Certificate
active
06772740
ABSTRACT:
INCORPORATION BY REFERENCE
The disclosure of Japanese Patent Application No. 2002-115336 filed on Apr. 17, 2002, including its specification, drawings, and abstract, is incorporated herein by reference in its entirety.
BACKGROUND OF THE INVENTION
1. Field of Invention
The invention relates to an evaporative fuel treating device and method, and more particularly, to an evaporative fuel treating device and method for treating evaporative fuel generated in a fuel tank of an internal combustion engine without discharging it into the atmosphere.
2. Description of Related Art
According to the art related to the invention, an evaporative fuel treating device having a canister for adsorbing evaporative fuel generated in a fuel tank is known as disclosed, for example, in Japanese Patent Application Laid-Open No. 10-274106. This device has a mechanism that purges evaporative fuel adsorbed in the canister through the flow of air and a separating membrane that separates evaporative fuel from purge gas. Furthermore, this device has a condensing unit for liquefying evaporative fuel separated by the separating membrane and a recirculation path for recirculating the condensed fuel back into the fuel tank. The evaporative fuel treating device thus constructed allows evaporative fuel generated in the fuel tank to be treated in a closed system including the canister. Thus, the above-mentioned device of the related art makes it possible to effectively prevent evaporative fuel from being discharged into the atmosphere without necessitating complicated control such as correction of fuel injection amount.
As described already, the above-mentioned device of the related art extracts evaporative fuel from purge gas by means of a separating membrane. However, the currently available separating membrane does not allow evaporative fuel having a sufficiently high concentration to be taken out from purge gas purged from the canister. If fuel gas having a low concentration is directly recirculated into the fuel tank, various inconveniences are caused due to the influence of air contained in fuel gas. Hence, the above-mentioned device of the related art is designed such that the condensing unit for condensing fuel gas is disposed in a post stage of the separating membrane.
As described hitherto, the above-mentioned device of the related art cannot produce high-concentration fuel gas by means of the separating membrane and thus requires that the condensing unit be disposed in the post stage of the separating membrane.
SUMMARY OF THE INVENTION
It is one object of the invention to provide an evaporative fuel treating device that can sufficiently condense evaporative fuel only through a treatment by separating membranes and that makes recirculation of evaporative fuel to a fuel tank possible without employing a condensing unit.
An evaporative fuel treating device for an internal combustion engine in accordance with a first aspect of the invention comprises a canister that adsorbs evaporative fuel generated in a fuel tank and a purge pump that causes canister outlet gas to flow out from the canister. In addition, a separating unit separates the canister outlet gas into treating gas containing a high concentration of evaporative fuel, circulating gas containing a medium concentration of evaporative fuel, and canister inlet gas containing a low concentration of evaporative fuel. A treating gas passage introduces the treating gas from the separating unit into the fuel tank. A circulating gas passage causes the circulating gas to circulate from the separating unit to a location upstream of the separating unit. A canister inlet gas passage causes the canister inlet gas to circulate from the separating unit to a location upstream of the canister.
According to the above-mentioned first aspect, canister outlet gas purged from the canister can be separated into high-concentration treating gas, medium-concentration circulating gas, and low-concentration canister inlet gas by being treated by the separating unit. In this case, medium-concentration circulating gas is circulated back through the separating unit and is repeatedly subjected to a concentrating processing. Thus, the first aspect makes it possible to make the concentration of treating gas sufficiently high and the concentration of canister inlet gas sufficiently low. Treating gas having a sufficiently high concentration can be utilized as fuel by being introduced into the fuel tank. Canister inlet gas having a sufficiently low concentration can be utilized as gas for purging evaporative fuel adsorbed in the canister by being introduced into the canister. Thus, the first aspect makes it possible to ensure that evaporative fuel adsorbed in the canister can be efficiently utilized as fuel.
In the above-mentioned first aspect, it is preferable that the purge pump include a purge gas circulation pump that communicates with the canister, that the separating unit include a high-concentration separation unit and a medium-concentration separation unit. It is preferable that the high-concentration separation unit have a first separating membrane for separating gas containing evaporative fuel into high-concentration gas containing a high concentration of evaporative fuel and low-concentration gas containing a low concentration of evaporative fuel and separate mixed gas composed of the canister outlet gas and the circulating gas into the treating gas and medium-concentration gas. It also is preferable that the medium-concentration separation unit be disposed downstream of the high-concentration separation unit, have a second separating membrane functioning in the same manner as the first separating membrane, and separate the medium-concentration gas into the circulating gas and the canister inlet gas. In this construction, canister outlet gas can be produced by the purge gas circulation pump. Further, high-concentration treating gas, medium-concentration circulating gas, and low-concentration canister inlet gas can be produced from canister outlet gas by using the high-concentration separation unit and the medium-concentration separation unit.
In the above-mentioned aspect, it is preferable that an area of the first separating membrane be smaller than an area of the second separating membrane. In this construction, it becomes possible to efficiently take out high-concentration treating gas during treatment of mixed gas by the first separating membrane and to efficiently take out low-concentration canister inlet gas during treatment of medium-concentration gas by the second separating membrane, by making the area of the first separating membrane included in the high-concentration separation unit smaller than the area of the second separating membrane included in the medium-concentration separation unit.
In the above-mentioned aspect, it is preferable that a ratio between the area of the first separating membrane and the area of the second separating membrane be set such that the treating gas and the canister inlet gas contain evaporative fuel having a concentration equal to or higher than 95% and evaporative fuel having a concentration equal to or lower than 5% respectively in the case where canister outlet gas contains evaporative fuel having a concentration of 15%. In this construction, since the ratio between the area of the first separating membrane and the area of the second separating membrane assumes a suitable value, the concentration of evaporative fuel contained in treating gas and the concentration of evaporative fuel contained in canister inlet gas can be made equal to or higher than 95% and equal to or lower than 5% respectively if the concentration of evaporative fuel contained in canister outlet gas is equal to or higher than 15%. Hence, a processing of liquefying evaporative fuel in the canister can be continued until the concentration of canister outlet gas reaches 15%.
In the above-mentioned aspect, it is preferable that the evaporative fuel treating device further comprise a feed pump that feeds fuel in the fuel tank to the internal combustion engine, and th
Aikawa Hidefumi
Kojima Susumu
Moulis Thomas N.
Toyota Jidosha & Kabushiki Kaisha
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