Receptacles – Closures – Sealing or closing means for vent or filling opening
Reexamination Certificate
2002-10-28
2004-12-28
Moy, Joseph Man-Fu (Department: 3727)
Receptacles
Closures
Sealing or closing means for vent or filling opening
C220S062220, C137S202000
Reexamination Certificate
active
06834771
ABSTRACT:
INCORPORATION BY REFERENCE
The disclosure of Japanese Patent Application No. 2000-271303 filed on Sep. 7, 2001, including the specification, drawings and abstract is incorporated herein by reference in its entirety.
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention relates to a welding structure for a resin component which allows reliable attachment of the component to a fuel tank and also inhibits leakage of fuel, or the like, within the fuel tank.
2. Description of Related Art
There is great demand for improvement in the air tightness of fuel tank systems for fuel tanks, and in particular, for fuel tanks of automobiles, in order to suppress emissions of hydrocarbon gases into the surrounding environment, at times of both running and stopping. In order to improve the sealing of the entire fuel tank system in this manner, a key problem which must be solved is reducing the amount of hydrocarbon gases that leaks from the fuel tank itself, as well as from each component part attached directly or indirectly to the fuel tank, or in other words, from the points, and so forth, to which, for example, a connecting pipe, a valve member, a pump or a filter are attached.
Furthermore, in order to bring about both weight reduction and cost reduction of automobiles, plasticization of fuel tanks has been promoted. At present, fuel tanks made from a high-density polyethylene resin that offers good corrosion prevention and is light weight have become mainstream. Moreover, in line with this, endeavors have also been made to plasticize each component attached directly and indirectly to the fuel tank. As a result, in order to make attachment to the fuel tank easy, the same resin material has been utilized in the attachment portion of each component and the fuel tank, and a method for connecting them using thermal welding has been adopted.
In light of these circumstances, the components described hereinafter are commonly used for fuel tanks and resin components attached to fuel tanks.
In order to achieve fuel tank weight reduction, the fuel tank is integrally molded by blow molding with resin. High density polyethylene resin (HDPE) is utilized since it is suitable for blow molding and offers excellent affordability and shock resistance. However, this high density polyethylene resin is known to permeate small amounts of hydrocarbon gases. Even though this permeation is limited, some sort of countermeasure to address it is desirable in order to respond to rising concerns regarding recent environmental pollution issues. The laminated structure of the fuel tank wall shown in
FIG. 12
has been proposed as a countermeasure.
In the figure, a fuel tank a is composed from a five layer structure that fundamentally includes a three layer structure having an inner shell b forming an inside portion of the tank, an outer shell c forming an outer portion of the tank, and a barrier layer d interposed between the shells b and c which prevents permeation of hydrocarbon gases. Bonding layers e, e are sandwiched between the barrier layer d and both of the shells b and c, respectively, in order to facilitate even stronger bonding of the respective resins.
More particularly, the inner shell b and the outer shell c use known high density polyethylene resin, and the bonding layers e, e use a highly advanced modified high density polyethylene resin having adhesive properties (this resin has adhesive properties and permeates hydrocarbon gases). The barrier layer d adopts a resin that prevents permeation by hydrocarbon gases, such as EVOH resin (EVAL) made by Kuraray Co., Ltd. Hydrocarbon gas emissions are suppressed very well using fuel tanks of this type.
A valve, intended as a part to be attached to a fuel tank, which is light and can be attached to the fuel tank and which reduces leakage of fuel, is disclosed in Japanese Patent Laid-Open Publication No. 10-71861. This valve is shown in FIG.
13
. This invention relates to a fuel leakage prevention valve for preventing leakage of fuel from a fuel tank, which occurs when an automobile turns over, or such like.
In this invention, a resin part p includes a valve cylinder portion q and an attachment portion r, these members being formed, respectively, from different materials. The valve cylinder portion q is formed from a polyacetal resin possessing great rigidity and capable of being formed with high dimensional accuracy, and includes a disk portion h which is integrally insert molded with an attachment portion r, and a valve cylinder g housing a fuel leakage prevention valve f. The attachment portion r is formed from the same high density polyethylene resin material as the fuel tank a, and has a flange j formed in an abutting portion which abuts against the fuel tank a. Furthermore, a pipe portion k connecting with a connection pipe m is formed on an opposite side of the attachment portion r to the flange j. In addition, a resin component p is composed from the valve cylinder portion q and the attachment portion r which are integrally formed by placing the disk portion h of the valve cylinder portion q in the die, and insert molding the attachment portion. The integrally formed valve cylinder portion q and the attachment portion r are strongly fixed by thermal welding an upper surface of the fuel tank a and a lower surface of the flange j of the attachment portion r, when the valve cylinder g is inserted in an open portion i of the fuel tank a.
However, as a result of the valve cylinder portion q and the attachment portion r being formed from different resins, even if both the valve cylinder portion q and the attachment portion r are integrally molded, there is a chance that a gap will emerge between the valve cylinder portion q and the attachment portion r due to vibrations caused by use, contractions due to temperature variation, deterioration with time, or the like, during usage after molding. In theory, the valve should function so as to prevent leakage of fuel from the tank, when the car turns over, or the like. However, if a gap is generated, fuel may leak at such times.
As well as this, since the attachment portion r is formed from the same high density polyethylene resin material as the fuel tank a, hydrocarbon gases can permeate through the attachment portion and are released to the outside.
Moreover, in Japanese Patent Laid-open No. HEI. 6-270701 a resin component, namely, a connection pipe, is disclosed. This connection pipe, as shown in
FIG. 14
, is formed from a first member s made from a polyamide resin, and a second member t made from a modified high density polyethylene resin. As a result of forming the second member t from the modified high density polyethylene resin, a flexible pipe is provided, and as well as this, attachment to the fuel tank can be executed with greater ease. Furthermore, since the second member t possesses cohesive properties, connection with the connecting portion w of the first member s is improved.
However, according to this structure, the second member t is formed from high density polyethylene resin. As a result, hydrocarbon gases permeate through the second member t and are released to the outside.
SUMMARY OF THE INVENTION
It is an object of the invention to provide a welding structure for a resin component which inhibits leakage of fuel and hydrocarbon gases from the resin component connected to a fuel tank.
In order to achieve the above object, a welding structure according to a first aspect of the invention is structured such that, a fuel tank having a resin inner shell and a resin outer shell which are interposed by a fuel permeation prevention layer so as to be laminated, is welded to a resin component for attachment to the fuel tank. The resin component includes a body formed of a resin having low permeability to hydrocarbon gases, a packing material having low permeability to hydrocarbon gases which is fixed to the body, and a resin which is insert molded to at least a connecting portion of the body which connects with a connecting portion of the tank, and which is weldable to the fuel tank.
According t
Muto Nobuharu
Suzuki Keiji
Kyosan Denki Co. Ltd.
Man-Fu Moy Joseph
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