Filter Arrangement for a Fuel Tank Comprising Shaped Mesh Sections

1. Field of the Invention

This invention relates to improvements in a filter arrangement disposed in a fuel tank and connected to a fuel pump in a fuel supply system, for example, of an automotive vehicle, and more particularly to such a filter arrangement which is prevented from collapsing even under vacuum due to sucking action of a fuel pump.

2. Description of the Prior Art

As a filter arrangement disposed inside a fuel tank and connected to a fuel pump, a variety of ones have been proposed and put into practical use. One of them is disclosed in Japanese Utility Model Provisional Publication No. 61-26617. In this publication, the filter arrangement includes a cap-shaped upper section located facing the upper side of a fuel tank. A lower section made of a mesh is connected to the open periphery of the cap-shaped upper section so that a hollow chamber is defined between the upper and lower sections. This filter arrangement is installed on a fuel pump at the suction port in such a manner that the lower section is spaced from the bottom inner surface of the fuel tank.

In this case, fuel between the lower section and the tank bottom inner surface cannot be effectively sucked into the fuel pump. In order to effectively suck the fuel in this region, the filter arrangement shown in FIG. 7 was conceived. In this filter arrangement, an upper section 2' and a lower section 3' both made of mesh are symmetrically formed, and secured to each other to form a bag-shaped filter 1'. The filter 1' is connected to a suction pipe 8' of a fuel pump 7' in such a manner as to be brought into elastic contact with the bottom inner surface of the fuel tank 4' so as to achieve vibration damping in addition to effective sucking of fuel.

Difficulties have been encountered even in such a filter 1', since the upper and lower sections 2', 3' unavoidably collapse inwards to come into contact with each other under a vacuum generated by the fuel pump 7'. As a result, the flow passage for fuel is blocked and the supply of fuel to the vehicle is cut off. In order to prevent such difficulties, the suction pipe 8' may be extended inside the filter 1' to suppress the collapse of the netting upper and lower section 2', 3' as indicated by phantom lines in FIG. 7. However, the extended suction pipe 8' tends to cause cavitation and vapor lock.

It is an object of the present invention to provide an improved filter arrangement, disposed inside a fuel tank, which can ensure a sufficient fuel flow passage therein even under the suction generated by a fuel pump positioned downstream of the filter arrangement.

The filter arrangement of the present invention includes a first section made of mesh disposed inside a fuel tank. A second section made of mesh is joined with the first section to define a space between it and the first section. The space is in communication with a fuel pump and filled with fuel filtered by the first and second sections. The first and second sections are different in shape from each other.

Accordingly, even if the upper and lower sections slightly deform inwardly under vacuum developed in the space during sucking by the fuel pump, the mades of deformation of the first and second sections are different from each other because of the fact the first and second sections are different in shape from each other. As a result, the first and second netting sections are prevented from being brought into contact with each other, and therefore fuel passage is maintained between the first and second sections.

FIG. 1 is a perspective view of an embodiment of a filter arrangement in accordance with the present invention;

FIG. 2 is a perspective view of the filter arrangement of FIG. 1 as viewed in the direction of arrow II;

FIG. 3 is a cross-sectional view taken along Line III--III of the filter arrangement of FIG. 1 as installed in a fuel tank, showing a cross-section of the filter arrangement taken in the direction of arrows substantially along the line III--III of FIG. 1;

FIG. 4 is a cross-sectional view of an installation state of the filter arrangement of FIG. 1 taken along line IV--IV, showing the filter arrangement as installed in a fuel tank;

FIG. 5 is a plan view of one example of a type of mesh which can be used for the filter arrangement of FIG. 1;

FIG. 6 is a cross-sectional view corresponding to FIG. 4 but illustrating the operation of the filter arrangement of FIG. 1; and

FIG. 7 is a schematic illustration of a conventional filter arrangement disposed inside a fuel tank.

FIG. 8 is a plan view of another example of a type of mesh which can be used for the filter arrangement of FIG. 1;

FIG. 9 is a plan view of yet another example of a type of mesh which can be used for the filter arrangement of FIG. 1;

FIG. 10 is a plan view of a flat piece of mesh which can be used to form a filter arrangement according to the present invention;

FIG. 11 is a plan view of another flat piece of mesh which can be used to form a filter arrangement according to the present invention.

Referring now to FIGS. 1 to 4, an embodiment of a filter arrangement according to the present invention is illustrated by reference character F. The filter arrangement F in this embodiment is disposed inside a fuel tank 4 of an automotive vehicle. The filter arrangement F comprises upper and lower sections 10, 11 which are formed of a mesh. The upper section 10 is generally flat and its shape in plan resembles an hourglass. Its longitudinal sides 12, 12 are arcuate so that the central portions of the sides 12, 12 are closer to one another than the end portions of the same edges. The lower section 11 is generally vessel-shaped and has an upper peripheral edge (not shown) corresponding to the continuous side edges 12, 13 of the upper section 10. The peripheral edge of the lower section 11 is connected to the upper section 10 at the side edges 12, 13.

The lower section 11 has an arcuate bottom profile as shown by the phantom lines in FIGS. 3 and 4 which are vertical cross-sectional views taken along Lines III--III and IV--IV, respectively, of FIG. 1. The curvature (1/R.sub.1, 1/R.sub.2, 1/R.sub.3) of the arcuate bottom profile in the vertical cross-section along Line IV--IV varies along Line III--III. In FIG. 2, R.sub.1, R.sub.2 and R.sub.3 denote respectively the radius of curvature of the arcuate bottom profile. Thus, the curvature of the arcuate bottom profile in the vertical cross-section along Line IV--IV becomes smaller from the central portion toward the end portion of the lower section 11. The curvature (1/R.sub.1) at the central portion is larger than those (1/R.sub.2, 1/R.sub.3) at the opposite end portions as shown in FIG. 2. Thus, the joined upper and lower sections 10, 11 of the filter arrangement F define a space 14 which is supplied with fuel filtered through the mesh of the upper and lower sections 10, 11.

The upper and lower sections can be formed of various types of mesh. Both sections need not be formed from the same type of mesh. FIG. 5 illustrates one example of a type of mesh which can be employed. This mesh is made of first linear fibers 15 and second linear fibers 16 which are woven generally perpendicular to the first linear fibers 15. The first linear fibers 15, which have a smaller diameter than the second linear fibers 16, extend in the longitudinal direction of the filter, i.e., parallel to Line III--III of FIG. 1.

FIG. 8 illustrates another example of a mesh which can be employed. This mesh has a plain weave in which all of the fibers have the same diameter.

FIG. 9 illustrates an example of another type of mesh which can be employed. This mesh has a twill weave with first linear fibers 17 and bundles of second linear fibers 18 which cross the first linear fibers 17 at right angles.

The fibers which form the mesh can be formed of various materials. Examples of suitable fibers are metal fibers made of a material such as stainless steel and plastic fibers made of a material such as nylon 6, polyvinyl dichloride, polypropylene, or polyethylene. A mesh can also be formed of a mixture of metal fibers and plastic fibers.

The diameters of the fibers can be chosen in accordance with the type of weave used to form the mesh and the desired rigidity of the mesh. An example of the mesh illustrated in FIG. 5 is one made of nylon 6 or polyvinyl dichloride with the first fibers 15 having a diameter of about 289 .mu.m and the second fibers 16 having a diameter of about 500 .mu.m.

An example of the mesh illustrated in FIG. 8 is one using fibers with a diameter of about 50 .mu.m made either of stainless steel or nylon 6.

An example of the mesh illustrated in FIG. 9 is one in which the first linear fibers 17 are monofilaments of polypropylene with a diameter of about 173 .mu.m, while the second linear fibers 18 are bundles of polyethylene fibers, each bundle having a diameter of about 165 .mu.m. Alternatively, both the first and second fibers can be made of nylon 6.

FIG. 10 is a plan view of a flat piece of mesh which can be used to form a filter like the one illustrated in FIG. 1. The mesh includes a section with the shape of an hourglass which becomes the upper section 10 of the filter and a rectangular section which becomes the lower section 11 of the filter. The upper section 10 has two parallel straight sides 10a having a length B and two concave sides 10b each having a length C. The lower section 11 has two straight sides 11a with a length B and two more straight sides 11b with a length D (C=D). One of sides 11a of the lower section 11 is integral with one of the straight sides 10a of the upper section 10. The width A of the upper section 10 at approximately midway along its length is less than the width B of the lower section 11. It is possible for the upper section 10 and the lower section 11 to be formed of two separate pieces of mesh which are joined together along one side. However, for ease of manufacture, the two sections are formed from a single flat piece of mesh.

The flat piece of mesh shown in FIG. 10 is formed into a filter by bending along the common side of the two sections 10 and 11 and then joining the remaining three sides of the lower section 11 to the corresponding three sides of the upper section 10 along their entire periphery. The two sections 10 and 11 can be joined by any suitable method. For example, if the mesh is made of a plastic material, the two sections can be directly joined using a suitable adhesive or by thermal fusion of the edges of the sections. If the mesh is made of a metal such as stainless steel, the two sections can be directly joined by brazing, soldering, or welding. Alternatively, the two sections can be joined to a frame having the same contour as the upper section 10. If the mesh is formed of plastic fibers, such as polyvinyl dichloride or nylon 6, the frame can be integrally formed with the mesh fibers from the same material. For example, in FIGS. 1 and 2, the peripheral edges 12 and 13 of the upper section 10 can be enlarged during the manufacture of the mesh to form an integral frame to which the lower section is attached.

Because the lower section 11 has a larger area than the upper section 10, when it is elastically deformed from its initially flat shape to join the edges of the two sections to one another, the lower sections bends away from the upper section 10 to define a space. The elasticity of the lower section 11 prevents the lower section 11 from collapsing against the upper section 10, even when it is subjected to external pressure during the operation of a fuel filter. Accordingly, it is not necessary to provide ribs or other stiffeners to keep the two sections separated from one another, so a fuel filter according to the present invention can be easily and inexpensively manufactured.

FIG. 11 illustrates another example of the shape of a flat piece of mesh which can be used to form a filter according to the present invention. In this example, the upper section 10 has a rectangular shape with two parallel straight sides 10a having a length A and two more parallel straight sides 10b having a length C. The initially flat lower section 11 has two parallel straight sides 11a with a length A and two convex sides 11b which connect the straight sides 11a with one another and curve away from one another. Each of the convex sides 11b has a length D (D=C). The width B of the lower section 11 at approximately midway along its length is greater than the width A of the upper section 10. The lower section 11 is joined to the upper section 10 along its entire periphery in the same manner as described with respect to FIG. 10.

A generally cylindrical connector 23 is fixedly secured to the upper section 10 in such a manner that the axis thereof is perpendicular to the flat upper section 10. The connector 23 extends into the space 14. The connector 23 is connected by a connecting pipe 20 with a suction pipe 22 of a fuel pump 21 shown in FIG. 3. The length of the connecting pipe 20 is such that the lower side section 11 of the filter arrangement F is brought into elastic contact with the bottom inner surface 5 of the fuel tank 4 so that the bottom profile of the lower side section 11 deforms from a state indicated by the phantom lines to a state indicated by the solid lines in FIG. 3.

A valve mechanism 30 is provided in the upper section 10 to discharge fuel vapor staying at the upper part of the space 14. The valve mechanism 30 includes a umbrella-shaped elastomeric valve member 32 having a vertically-extending central rod secured to a base 31 fixedly mounted to the upper section 10. The base 31 is formed with a plurality of through-holes 31a which are closable by the peripheral or flap section of the valve member 31. The peripheral section of the valve member 31 deforms upwardly to open the through-holes 31a under the pressure of fuel vapor which is supplied from the fuel pump suction pipe 22 into the space 14, thereby releasing the fuel vapor from the space 14. This prevents vapor lock caused by sucking the fuel vapor into the fuel pump 21. When fuel is sucked by the fuel pump 21, the peripheral section of the valve member 32 is pressed against the base 31 to close the through-holes 31a. The flat upper section 10 facilitates formation of the installation sections for the connector 23 and the valve mechanism 30 thereto, and therefore facilitates the installation of these members on the upper section 10.

The manner of operation of the filter arrangement F will be discussed hereinafter.

When the fuel pump 21 is stopped, the lower section 11 of the filter arrangement F is pressed against the bottom inner surface 5 of the fuel tank 4 so and deforms as shown in FIGS. 3 and 4. Since the lower section 11 has a high rigidity and restoring force due to its arcuate bottom profile, the space 14 is maintained when the lower section 11 contacts the bottom inner surface 5 of the tank 4. Additionally, the filter arrangement F is directly in elastic contact with the bottom inner surface 5 of the fuel tank 4, and therefore vibrations and the like applied to the filter arrangement F can be effectively absorbed without necessitating any separate vibration damping member such as a coil spring.

During operation of the fuel pump 21, fuel in the fuel tank 4 is sucked through the filter arrangement F to the fuel pump 21 so a vacuum is developed within the space 14. At this time, the upper and lower sections 10, 11 of the filter arrangement F deforms toward the inside of the space 14. As shown by the phantom lines in FIG. 6, the upper section 10 is gently depressed while the lower section 11 deforms upwardly at its central section 11a while the rest of the lower section 11 is in contact with the bottom inner surface 5 of the fuel tank 4. However, the upper side section 10 only slightly deforms and is prevented from collapsing since it is flat and supported at the joint 19 between it and the lower section 11. The lower side section 11 is also prevented from collapsing or greatly deforming since its rigidity is high owing to its arcuate bottom profile in cross-section. Furthermore, the upper and lower sections 10, 11 of the filter arrangement F have a high in rigidity also owing to the fact that they are formed of the woven netting constituted of the wider linear materials 16, thereby suppressing deformation of the upper and lower sections 10, 11 of the filter arrangement F. Moreover, since the curvature of arcuate bottom profile of the lower side section 11 is not uniform throughout the length thereof and decreases from its central portion to its end portions, the state of the inward deformation at these portions is not uniform and therefore the space 14 can be reliably maintained, particularly at the portion which has a slight deformation. Thus, the upper and lower sections 10, 11 can be effectively prevented from collapsing. In addition, the difference in the manner of deforming of the upper and lower sections 10, 11 reliably prevents the upper and lower sections 10, 11 from contacting each other, thus maintaining a fuel flow passage even under suction by the fuel pump 21.

In FIG. 3, the filter is shown disposed with the lower section 11 resting on the bottom surface 5 of a fuel tank 4. However, it is also possible to mount the filter so that the lower section 11 is suspended above the bottom surface 5. In this case, when there is movement of the vehicle in which the fuel tank 4 is mounted, the filter will be subjected to vibrations. Because of the elasticity of the lower section 11, it will expand and contract with the vibrations, and this movement of the lower section 11 will dislodge dirt and the like adhering to the mesh. The dislodged dirt will then settle to the bottom of the fuel tank 4. As a result, the surface of the filter is automatically cleaned and can be prevented from becoming clogged with dirt.

Normally, it is desirable that the inlet to the connecting pipe 20 be near to the bottom of the fuel tank 4 to suck fuel even when the fuel tank 4 is nearly empty. For this reason, a fuel filter according to the present invention is constructed so that it can be installed on the bottom surface of a fuel tank 4. Since the lower section 11 of the filter is elastic, it can expand or contract to compensate for variations in the length of the connecting pipe 20 or for thermal expansion of the connecting pipe 20 during operation. Therefore, it is not necessary to install a sliding joint or an expansion joint between the connecting pipe 20 and the filter or the fuel pump 21, the length of the connecting pipe 20 does not need to be precise, the connecting pipe 20 can be easily connected between the filter and the fuel pump 22, and thermal stresses are not generated due to expansion of parts.

In conventional filter arrangements employing ribs or rigid separating members to prevent the filter sections from coming into contact with one another when subjected to pressure, considerable noise may be generated due to contact of these members with the bottom surface of a fuel tank. A filter arrangement according to the present invention does not require ribs or other support members, so it does not produce noise when the vehicle is cruising.