Abstract:
A filter includes upper and lower filter members that form at least two opposed surfaces that face each other, a porous member contained in the filter member, and a coupling member having an opening that is open to the porous member so that the porous member communicates with the coupling member. In the filter, the filter member removes foreign matters contained in liquid, and the liquid from which the foreign matters are removed is discharged through the porous member and the coupling member.

Description:
INCORPORATION BY REFERENCE  
         [0001]    The disclosure of Japanese Patent Application No. 2000-392310 filed on Dec. 25, 2000 including the specification, drawings and abstract is incorporated herein by reference in its entirety.  
         BACKGROUND OF THE INVENTION  
         [0002]    1. Field of the Invention  
           [0003]    The invention generally relates to the structure of a filter, and more particularly to the structure of an in-tank type fuel filter installed in a fuel tank of a motor vehicle, such as an automobile.  
           [0004]    2. Description of Related Art  
           [0005]    A known example of an in-tank type fuel filter installed in a fuel tank of a motor vehicle will be hereinafter described with reference to FIG. 7 and FIG. 8.  
           [0006]    [0006]FIG. 7 shows a fuel tank  1  installed in a motor vehicle, such as an automobile. A fuel pump  3  for delivering fuel to a fuel injection system  4  is disposed in the fuel tank  1 . A fuel filter  2  is attached to a coupling member  7 , which in turn is attached to the fuel inlet side or upstream side of the fuel pump  3 .  
           [0007]    The fuel filter  2  is illustrated in detail in FIG. 8. One of the opposite ends of the fuel filter  2  is coupled to the fuel pump  3  via the coupling member  7 , while the other end of the fuel filter  2  abuts on a bottom wall  9  of the fuel tank  1 . With this arrangement, the fuel pump  3  is able to pump up a sufficient amount of fuel even when the level of the fuel in the fuel tank  1  is lowered.  
           [0008]    The fuel filter  2  includes a filter member  5  and a protector  6  disposed inside the filter member  5 . The filter member  5  consists of a mesh screen that is formed of a synthetic resin and has a multiplicity of apertures formed therein. The protector  6 , which is formed of a synthetic resin, functions to prevent adhesion of two or more sheets of the filter member  5 , and ensure a sufficiently large volume of inner space  8  so that a fuel passage can be surely formed in the fuel filter  2 .  
           [0009]    The know fuel filter  2  as described above is advantageous in that the protector  6  can prevent adhesion of two or more sheets of the filter member  5  to thereby ensure a sufficient volume of inner space  8 . In addition, the protector  6  serves to press the filter member  5  of the fuel filter  2  against the bottom wall  9  of the fuel tank  1 .  
           [0010]    The known fuel filter  2 , however, has the following problems. First of all, the provision of the protector  6  results in increases in the overall weight and cost of the fuel filter  2 . Secondly, the rigidity of the protector  6  is utilized to press the fuel filter  2  (more specifically, the filter member  5 ) against the bottom wall  9  of the fuel tank  1 , and therefore the filter member  5  is likely to wear, and suffers from a reduced durability. In addition, vibrations of the fuel pump  3  are transmitted to the fuel tank  1  via the protector  6 , causing abnormal or unusual noise and making a passenger of the vehicle feel uncomfortable.  
           [0011]    Furthermore, the protector  6 , which is molded out of a synthetic resin, undergoes deformation (e.g., warpage) when it is immersed in the fuel, and the filter member  5  also deforms along with the protector  6 . As a result, the durability of the filter member  5  may deteriorate.  
           [0012]    In addition, a corner portion of the protector  6  abrades a portion of the filter member  5  that is in contact with the bottom wall  9  of the fuel tank  1 , possibly causing early wear and damage of the filter member  5 .  
         SUMMARY OF THE INVENTION  
         [0013]    It is therefore an object of the invention to provide a filter that is available at a reduced cost, compact in size, and has an improved durability.  
           [0014]    To accomplish the above and/or other objects, there is provided according to one aspect of the invention, which provides a filter that includes (a) at least one filter member that forms at least two opposed surfaces that face each other, (b) at least one porous member contained in the at least one filter member, and (c) a coupling member having an opening that is open to the at least one porous member so that the porous member communicates with the coupling member. In the filter, the filter member removes foreign matters contained in a liquid, and the liquid from which the foreign matters are removed is discharged through the porous member and the coupling member. With this arrangement, the filter is sure to be provided with sufficiently large inner space and fuel passage(s), without requiring the protector as used in the known filter. Thus, the filter does not suffer from wear that would be otherwise caused by the protector, and therefore the service life of the filter is increased or extended.  
           [0015]    In one embodiment of the invention, the filter has a three-layer structure having first and second filter members, and a porous member, which structure is constructed such that the first and second filter members cover upper and lower surfaces of the porous member, respectively. In another embodiment of the invention, the filter has a four-layer structure having first and second filter members and first and second porous members, in which one surface of the first porous member that is not covered by the first filter member is superposed on one surface of the second porous member that is not covered by the second filter member. In a further embodiment of the invention, the filter has a four-layer structure that is formed by bending a two-layer structure comprising one porous member and one filter member covering one surface of the porous member, at a substantially middle portion of the two-layer structure. In any of these embodiments, the filter is surely provided with sufficiently large inner space and fuel passage(s), without requiring the protector as used in the known filter. Thus, the filter does not suffer from wear that would be otherwise caused by the protector, and therefore the service life of the filter is prolonged or extended. Furthermore, the filter can be manufactured in a simplified manner at a reduced cost.  
           [0016]    The filter member as indicated above may be formed of filter paper or a non-woven fabric. In this case, the weight of the filter as a whole can be reduced, and the filter can be manufactured in a simplified manner at a reduced cost.  
           [0017]    The filter member as indicated above may also be formed from a non-woven fabric and a mesh screen. With the filter member thus formed, the durability of the filter is enhanced, and wear of the filter member, especially when pressed against the bottom wall of the fuel tank, can be advantageously reduced or mitigated. Consequently, the service life of the filter can be prolonged.  
           [0018]    In another embodiment of the invention, the coupling member is provided on the upper one of the filter members. With this arrangement, the entire area of the lower filter member is able to abut on the bottom wall of the fuel tank, so that the filter can pump up fuel without fail even if the fuel level in the tank is lowered.  
           [0019]    In a still another embodiment of the invention, the coupling member extends from the upper filter member to the lower filter member. In this case, the coupling member can surely hold the filter, while preventing deformation thereof.  
           [0020]    In a yet another embodiment of the invention, the coupling member is provided on a side face of the filter member. With this arrangement, a fuel pump disposed within the fuel tank can be located in the vicinity of the inner wall of the fuel tank. Thus, the mounting position of the fuel pump can be determined with increased flexibility. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0021]    The foregoing and/or further objects, features and advantages of the invention will become more apparent from the following description of preferred embodiments with reference to the accompanying drawings, in which like numerals are used to represent like elements and wherein:  
         [0022]    [0022]FIG. 1 is a cross-sectional view showing a fuel filter according to a first embodiment of the invention;  
         [0023]    [0023]FIG. 2 is a cross-sectional view showing a fuel filter according to a second embodiment of the invention;  
         [0024]    [0024]FIG. 3 is a cross-sectional view showing a fuel filter according to a third embodiment of the invention;  
         [0025]    [0025]FIG. 4 is a cross-sectional view showing a fuel filter according to a fourth embodiment of the invention;  
         [0026]    [0026]FIG. 5 is a cross-sectional view showing a fuel filter according to a fifth embodiment of the invention;  
         [0027]    [0027]FIG. 6 is a cross-sectional view showing a fuel filter according to a sixth embodiment of the invention;  
         [0028]    [0028]FIG. 7 is a cross-sectional view showing a state in which a known in-tank type fuel filter is mounted in position; and  
         [0029]    [0029]FIG. 8 is a cross-sectional view showing the in-tank type fuel filter of FIG. 7 in detail. 
     
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS  
       [0030]    First Embodiment  
         [0031]    [0031]FIG. 1 illustrates an in-tank type fuel filter  10  according to a first embodiment of the invention. The fuel filter  10  has a generally rectangular shape as viewed in a plane perpendicular to the sheet of FIG. 1. The fuel filter  10  is coupled, via a coupling member  13 , to the upstream side of a fuel pump installed in a fuel tank of a motor vehicle.  
         [0032]    The fuel filter  10  includes an upper filter member  11 , a lower filter member  12 , a porous member  14  disposed between the filter members  11 ,  12 , and the coupling member  13 . The upper and lower filter members  11 ,  12  are formed by cutting filter paper or a non-woven fabric into a predetermined shape so that these filter members  11 ,  12  have substantially the same shape. A peripheral portion  15  is formed at a periphery of each of the filter members  11 ,  12 , and openings  11   b,    12   b  for receiving an end portion of the coupling member  13  are formed through central portions of the filter members  11 ,  12 , respectively. The non-woven fabric is preferably formed by mixing raw fibers with adhesive fibers. The raw fibers may be selected from polyester, polypropylene, rayon, glass, acetate and others. The adhesive fibers may be formed by coating fibers of polyester, polypropylene, rayon, glass, acetate, or the like, with a low-melting-point resin, such as modified polyester, modified polyethylene, modified polypropylene, or the like.  
         [0033]    The porous member  14  may be a foamed member, a sponge-like member, or the like, which is made of a material, such as polyester, nylon, or polypropylene, as widely known in the art. Namely, the porous member  14  may be formed from any type of member provided that it forms oil paths through which the fuel is allowed to flow without any difficulty, and that it is able to retain its original shape. In fabricating the fuel filter  10 , the porous member  14  is first formed in the shape of a flat plate whose thickness is substantially equal to that of the filter  10 , and is then cut into a suitable shape in accordance with the shape of the upper and lower filter members  11 ,  12 . Then, a bore  14   a  is formed through a central portion of the porous member  14 , so that the coupling member  13  can be fitted in the bore  14   a  as described later.  
         [0034]    Subsequently, the porous member  14  is interposed between the upper filter member  11  and the lower filter member  12 . The peripheral portions  15  of the upper filter member  11  and the lower filter member  12  are welded onto a peripheral portion of the porous member  14  by a thermal welding means, such as ultrasonic welding or electrodeposition, while force is being applied from the upper and lower sides of the filter members  11 ,  12 . In this manner, the porous member  14  fills the inner space between the filter members  11 ,  12 , to thus form fuel paths in the filter  10 .  
         [0035]    In the first embodiment as described above, the peripheral portion of the porous member  14  is formed simultaneously with the peripheral portions of the upper filter member  11  and the lower filter member  12  through the thermal welding means. However, the upper and lower filter members  11 ,  12  and the porous member  14  may be initially formed into a three-layer integral sheet, which is then cut into a suitable shape, with its periphery welded by a thermal welding means, such as ultrasonic welding or electrodeposition.  
         [0036]    The coupling member  13  consists of an upper member  13   a  having a flange  13   b,  and a lower member  13   c  having a flange  13   d.  The upper and lower members  13   a,    13   c  are inserted from the upper side and the lower side of the filter  10  into the bore  14   a  of the porous member  14 , through the openings  11   b,    12   b  of the upper filer member  11  and the lower filter member  12 , respectively. Then, the upper and lower members  13   a,    13   c  are integrated together with their end faces secured to each other with an adhesive, or the like. A plurality of semicircular openings that provide fuel passages are formed in portions of the upper member  13   a  and the lower member  13   c  adjacent to their end faces, so that a plurality of fuel inlets  13   e  are formed when the end faces of the upper and lower members  13   a,    13   b  abut on each other.  
         [0037]    The flanges  13   b,    13   d  are fixed or secured at their corresponding faces to the upper filter member  11  and the lower filter member  12 , respectively, by an adhesive or any other bonding means, so that deformation of the filter  10  can be prevented or suppressed. While the filter  10  has a generally rectangular shape in the first embodiment, the filter may have a circular shape, or any other shape.  
         [0038]    Second Embodiment  
         [0039]    [0039]FIG. 2 illustrates an in-tank type fuel filter  20  according to a second embodiment of the invention. The fuel filter  20  has a generally rectangular shape as viewed in a plane perpendicular to the sheet of FIG. 2. The fuel filter  20  is coupled, via a coupling member  13 , to the upstream side of a fuel pump installed in a fuel tank of a motor vehicle.  
         [0040]    The fuel filter  20  includes an upper filter member  11 , a lower filter member  12 , two-layer porous members  24 ,  26  disposed between the filter members  11 ,  12 , and the coupling member  13 . The upper and lower filter members  11 ,  12  are formed by cutting filter paper or a non-woven fabric into a predetermined shape so that these filter members  11 ,  12  have the same shape. A peripheral portion  15  is formed at a periphery of each of the filter members  11 ,  12 , and openings  11   b,    12   b  for receiving an end portion of the coupling member  13  are formed through central portions of the filter members  11 ,  12 , respectively.  
         [0041]    Each of the porous members  24 ,  26  may be a foamed member, a sponge-like member, or the like, which is made of a material, such as polyester, nylon, or polypropylene, as widely known in the art. Namely, the porous member  24 ,  26  may be formed from any type of member provided that it forms oil paths through which the fuel is allowed to flow without any difficulty, and that it is able to retain its original shape. In fabricating the fuel filter  20 , each of the porous members  24 ,  26  is first formed in the shape of a flat plate whose thickness is substantially a half of the thickness of the filter  20 . One surface of the porous member  24  is bonded to the upper filter member  11  with an adhesive, or the like, and one surface of the porous member  26  is bonded to the lower filter member  12  with an adhesive, or the like. Thus, a pair of two-layer assemblies, i.e., an assembly of the porous member  24  and the upper filter member  11  and an assembly of the porous member  26  and the lower filter member  12 , are prepared. Then, bores  24   a,    26   a  for receiving the coupling member  13  are formed through central portions of the porous members  24 ,  26 .  
         [0042]    Subsequently, the porous members  24 ,  26  are superposed on each other so as to form a four-layer structure. Then, the peripheral portions  15  of the upper filter member  11  and the lower filter member  12  are welded onto peripheral portions of the porous members  24 ,  26  by thermal welding means, such as ultrasonic welding or electrodeposition, while force is being applied from the upper and lower sides of the filter members  11 ,  12 . In this manner, the porous members  24 ,  26  fill the inner space between the filter members  11 ,  12 , to thus form fuel paths in the filter  20 .  
         [0043]    In the second embodiment as described above, the peripheral portions of the porous members  24 ,  26  are formed simultaneously with the peripheral portions of the upper filter member  11  and the lower filter member  12  through the thermal welding means. However, two-layer integral sheets each consisting of a filter member and a porous member may be initially prepared, and cut into a suitable shape. Then, the porous members of the resulting cut sheets are superposed on each other, with the peripheries of the cut sheets welded together by thermal welding means, such as ultrasonic welding or electrodeposition.  
         [0044]    The coupling member  13  consists of an upper member  13   a  having a flange  13   b,  and a lower member  13   c  having a flange  13   d.  The upper and lower members  13   a,    13   c  are inserted from the upper side and the lower side of the filter  20  into the bores  24   a,    26   a  of the porous members  24 ,  26 , through the openings  11   b,    12   b  of the upper filer member  11  and the lower filter member  12 , respectively. Then, the upper and lower members  13   a,    13   c  are integrated together with their end faces secured to each other by an adhesive, or the like. A plurality of semicircular openings that provide fuel passages are formed in portions of the upper member  13   a  and the lower member  13   c  adjacent to their end faces, so that a plurality of fuel inlets  13   e  are formed when the end faces of the upper and lower members  13   a,    13   b  abut on each other.  
         [0045]    The flanges  13   b,    13   d  are fixed at their corresponding faces to the upper filter member  11  and the lower filter member  12 , respectively, by an adhesive or any other bonding means, so that deformation of the filter  20  can be prevented or suppressed. While the filter  10  has a generally rectangular shape in the second embodiment, the filter may have a circular shape, or any other shape.  
         [0046]    Third Embodiment  
         [0047]    [0047]FIG. 3 illustrates an in-tank type fuel filter  30  according to a third embodiment of the invention. The fuel filter  30  has a four-layer structure formed by folding a two-layer integral sheet consisting of a filter member and a porous member.  
         [0048]    The in-tank type fuel filter  30  has a generally rectangular shape as viewed in a plane perpendicular to the sheet of FIG. 3. The fuel filter  30  is coupled, via a coupling member  13 , to the upstream side of a fuel pump installed in a fuel tank of a motor vehicle.  
         [0049]    The fuel filter  30  includes a filter member  31 , two-layer porous member  34  disposed between the upper half  31   a  and the lower half  31   b  of the filter member  31 , and the coupling member  13 . The filter member  31  is formed by cutting filter paper or a non-woven fabric into a predetermined shape having a length that is twice as large as the length of the filter  30 . A peripheral portion  15  is formed at a periphery of the filter member  31 , and openings  11   b,    12   b  for receiving an end portion of the coupling member  13  are formed through portions of the filter member  31  that are spaced apart from the longitudinally opposite end faces thereof by a distance equal to one-fourth of the length of the filter  30 .  
         [0050]    The two-layer porous member  34  may be a foamed member, a sponge-like member, or the like, which is made of a material, such as polyester, nylon, or polypropylene, as widely known in the art. Namely, the porous member  34  may be formed from any type of member provided that it forms oil paths through which the fuel is allowed to flow without any difficulty, and that it is able to retain its original shape. In fabricating the fuel filter  30 , the porous member  34  is first formed in the shape of a flat plate whose thickness is a half of the thickness of the filter  30 , and whose length is twice the length of the filter  30 . Then, bores  34   a  for receiving the coupling member  13  are formed through portions of the porous member  34  that are spaced apart from the longitudinally opposite end faces thereof by a distance equal to one-fourth of the length of the filter  30 .  
         [0051]    Subsequently, one surface of the porous member  34  is bonded to one surface of the filter member  31  by an adhesive, or the like, to form a two-layer structure, which is then folded at a longitudinally middle portion thereof with one half of the porous member  34  facing the other half, thereby to provide a four-layer structure. Thus, the upper half  31   a  and the lower half  31   b  of the filter member  31  are formed. Then, the peripheral portions  15  of the upper half  31   a  and lower half  31   b  of the filter member  31  except its folded portion are welded onto a peripheral portion of the porous member  34  by thermal welding means, such as ultrasonic welding or electrodeposition, while force is being applied from the upper and lower sides of the filter member  31 . In this manner, the porous member  34  fills the inner space between the upper half  31   a  and lower half  31   b  of the filter member  31 , to thus form fuel paths in the filter  30 .  
         [0052]    In the third embodiment as described above, the peripheral portion of the porous member  34  except its folded portion is formed simultaneously with the peripheral portions of the upper half  31   a  and the lower half  31   b  of the filter member  31  through the thermal welding means. However, a two-layer integral sheet consisting of a filter member and a porous member and having a length that is about twice the length of the filter  30  may be initially prepared, and then cut into a suitable shape after being folded once. Then, the periphery of the two-layer sheet is welded by thermal welding means, such as ultrasonic welding or electrodeposition.  
         [0053]    The coupling member  13  consists of an upper member  13   a  having a flange  13   b,  and a lower member  13   c  having a flange  13   d.  The upper and lower members  13   a,    13   c  are inserted from the upper side and the lower side of the filter  30  into the bores  34   a  of the porous member  34 , through the openings  11   b,    12   b  of the filter member  31 , respectively. Then, the upper and lower members  13   a,    13   c  are integrated together with their end faces secured to each other with an adhesive, or the like. A plurality of semicircular openings that provide fuel passages are formed in portions of the upper member  13   a  and the lower member  13   c  adjacent to their end faces, so that a plurality of fuel inlets  13   e  are formed when the end faces of the upper and lower members  13   a,    13   b  abut on each other.  
         [0054]    The flanges  13   b,    13   d  are fixed at their corresponding faces to the upper half  31   a  and the lower half  31   b  of the filter member  31 , respectively, by an adhesive or any other bonding means, so that deformation of the filter  30  can be prevented or suppressed. While the filter  10  has a generally rectangular shape in the second embodiment, the filter may have any other shape provided that the folded portion is formed straight.  
         [0055]    Fourth Embodiment  
         [0056]    [0056]FIG. 4 illustrates an in-tank type fuel filter  40  according to a fourth embodiment of the invention. The fuel filter  40  has a generally rectangular shape as viewed in a plane perpendicular to the sheet of FIG. 4. The fuel filter  40  is coupled, via a coupling member  43 , to the upstream side of a fuel pump installed in a fuel tank of a motor vehicle.  
         [0057]    The fuel filter  40  includes an upper filter member  11 , a lower filter member  12 , a porous member  14  disposed between the filter members  11 ,  12  and the coupling member  43 . The upper and lower filter members  11 ,  12  are formed by cutting filter paper or a non-woven fabric into a predetermined shape so that these filter members  11 ,  12  have substantially the same shape. A peripheral portion  15  is formed at a periphery of each of the filter members  11 ,  12 , and an opening  11   b  for receiving an end portion of the coupling member  43  is formed through a central portion of the filter member  11 .  
         [0058]    The porous member  14  may be a foamed member, a sponge-like member, or the like, which is made of a material, such as polyester, nylon, or polypropylene, as widely known in the art. Namely, the porous member  14  may be formed from any type of member provided that it forms oil paths through which the fuel is allowed to flow without any difficulty, and that it is able to retain its original shape. In fabricating the fuel filter  40 , the porous member  14  is first formed in the shape of a flat plate whose thickness is substantially equal to that of the filter  40 , and is then cut into a suitable shape in accordance with the shape of the upper and lower filter members  11 ,  12 .  
         [0059]    Subsequently, the porous member  14  is interposed between the upper filter member  11  and the lower filter member  12 . The peripheral portions  15  of the upper filter member  11  and the lower filter member  12  are welded onto a peripheral portion of the porous member  14  by thermal welding means, such as ultrasonic welding or electrodeposition, while force is being applied from the upper and lower sides of the filter members  11 ,  12  to the peripheral portions  15 . In this manner, the porous member  14  fills the inner space between the filter members  11 ,  12 , to thus form fuel paths in the filter  40 .  
         [0060]    In the fourth embodiment as described above, the peripheral portion of the porous member  14  is formed simultaneously with the peripheral portions of the upper filter member  11  and the lower filter member  12  through the thermal welding means. However, the porous member  14  may be initially formed into a shape corresponding to that of the inner space of the filter  40 , and the peripheral portions  15  of the upper and lower filter members  11 ,  12  may be welded together by thermal welding means, such as ultrasonic welding or electrodeposition.  
         [0061]    The coupling member  43  consists of a pipe-like member  43   f  having a flange  43   b  formed around a lower portion of the member  43   f.  The coupling member  43  and the upper filter member  11  are integrated with each other by aligning a hollow portion of the pipe-like member  43   f  with the opening  11   b  of the upper filter member  11 , and fixing or securing the lower end face of the flange  43   b  to the upper surface of the upper filter member  11  with an adhesive, or the like.  
         [0062]    Since the fuel filter  40  is not provided with the lower member  13   c  of the coupling member  13  provided at the bottom of the filter  10 ,  20 ,  30  as shown in FIG. 1 through FIG. 3, the fuel filter  40  surely abuts on the bottom of the fuel tank, so that the fuel in the fuel tank can be pumped up without fail.  
         [0063]    While the fourth embodiment of the invention is a modified example of the first embodiment as described above, the second and third embodiments of the invention may also be modified in the same manner, by employing the coupling member  43  having only the upper flange  43   b.  Furthermore, while the filter  40  has a generally rectangular shape in the fourth embodiment, the filter may have a circular shape, or any other shape.  
         [0064]    Fifth Embodiment  
         [0065]    [0065]FIG. 5 illustrates an in-tank type fuel filter  50  according to a fifth embodiment of the invention. In this embodiment, the coupling member  43  is provided on the upper filter member  11  like the fourth embodiment, and a mesh screen is further provided on the lower surface of the lower filter member  12  so as to reinforce the bottom portion of the filter  50 .  
         [0066]    The fuel filter  50  has a generally rectangular shape as viewed in a plane perpendicular to the sheet of FIG. 5. The fuel filter  50  is coupled, via the coupling member  43 , to the upstream side of a fuel pump installed in a fuel tank of a motor vehicle.  
         [0067]    The fuel filter  50  includes an upper filter member  11 , a lower filter member  12 , a porous member  14  disposed between the filter members  11 ,  12 , and the coupling member  43 . The upper and lower filter members  11 ,  12  are formed by cutting filter paper or a non-woven fabric into a predetermined shape so that these filter members  11 ,  12  have substantially the same shape. A peripheral portion  15  is formed at a periphery of each of the filter members  11 ,  12 , and an opening  11   b  for receiving an end portion of the coupling member  43  is formed through a central portion of the filter member  11 .  
         [0068]    The porous member  14  may be a foamed member, a sponge-like member, or the like, which is made of a material, such as polyester, nylon, or polypropylene, as widely known in the art. Namely, the porous member  14  may be formed from any type of member provided that it forms oil paths through which the fuel is allowed to flow without any difficulty, and that it is able to retain its original shape. In fabricating the fuel filter  50 , the porous member  14  is first formed in the shape of a flat plate whose thickness is substantially equal to that of the filter  50 , and is then cut into a suitable shape in accordance with the shape of the upper and lower filter members  11 ,  12 .  
         [0069]    Subsequently, the porous member  14  is interposed between the upper filter member  11  and the lower filter member  12 . The peripheral portions  15  of the upper filter member  11  and the lower filter member  12  are welded onto a peripheral portion of the porous member  14  by thermal welding means, such as ultrasonic welding or electrodeposition, while force is being applied from the upper and lower sides of the filter members  11 ,  12  to the peripheral portions  15 . In this manner, the porous member  14  fills the inner space between the filter members  11 ,  12 , to thus form fuel paths in the filter  50 .  
         [0070]    In the fifth embodiment as described above, the peripheral portion of the porous member  14  is formed simultaneously with the peripheral portions of the upper filter member  11  and the lower filter member  12  through the thermal welding means. However, the porous member  14  may be initially formed into a shape corresponding to that of the inner space of the filter  50 , and the peripheral portions  15  of the upper and lower filter members  11 ,  12  may be welded together by thermal welding means, such as ultrasonic welding or electrodeposition.  
         [0071]    The coupling member  43  consists of a pipe-like member  43   f  having a flange  43   b  formed around a lower portion of the member  43   f.  The coupling member  43  and the upper filter member  11  are integrated with each other by aligning a hollow portion of the pipe-like member  43   f  with the opening  11   b  of the upper filter member  11 , and fixing the lower end face of the flange  43   b  to the upper surface of the upper filter member  11  by an adhesive, or the like. Then, a mesh screen  16  is fixed or secured to the entire area of the lower surface of the lower filter member  12  by fixing means, such as an adhesive. The mesh screen  16 , which is made of a synthetic resin, may be a roughly woven sheet having a multiplicity of holes, or may be a thin, flat sheet having a multiplicity of holes.  
         [0072]    In the above-described fourth embodiment, the lower filter member  12 , if it is made from filter paper, may wear due to friction or abrasion between the lower filter member and the bottom wall of the fuel tank. In the fifth embodiment constructed as described above, on the other hand, the lower filter member  12  is less likely to wear due to abrasion, and the durability of the fuel filter  50  is improved.  
         [0073]    While the fifth embodiment of the invention is a modified example of the first embodiment as described above, the second and third embodiments of the invention may also be modified in the same manner, by employing the coupling member  43  having only the upper flange  43   b  and the mesh screen  16  provided on the lower filter member  12 . Furthermore, while the filter  50  has a generally rectangular shape in the fifth embodiment, the filter may have a circular shape, or any other shape.  
         [0074]    Sixth Embodiment  
         [0075]    [0075]FIG. 6 illustrates an in-tank type fuel filter  60  according to a sixth embodiment of the invention. The fuel filter  60  has a four-layer structure like the fuel filter  30  of the third embodiment, but is different from the filter  30  in that a coupling member is attached to one side face of the filter  60 .  
         [0076]    The in-tank type fuel filter  60  has a generally rectangular shape as viewed in a plane perpendicular to the sheet of FIG. 6. The fuel filter  60  is coupled, via a coupling member  63 , to the upstream side of a fuel pump installed in a fuel tank of a motor vehicle.  
         [0077]    The fuel filter  60  includes an upper filter member  61   a,  a lower filter member  61   b,  a two-layer porous member  64  disposed between the upper filter member  61   a  and the lower filter member  61   b,  and the coupling member  63 . The upper and lower filter members  61  are formed by cutting filter paper or a non-woven fabric into a predetermined shape having a length that is twice the length of the fuel filter  60 . A peripheral portion  15  is formed at a periphery of the filter members  61   a,    61   b.    
         [0078]    The two-layer porous member  64  may be a foamed member, a sponge-like member, or the like, which is made of a material, such as polyester, nylon, or polypropylene, as widely known in the art. Namely, the porous member  64  may be formed from any type of member provided that it forms oil paths through which the fuel is allowed to flow without any difficulty, and is also able to retain its original shape. In fabricating the fuel filter  60 , the porous member  64  is first formed in the shape of a flat plate whose thickness is a half of the thickness of the filter  60 , and whose length is twice the length of the filter  60 .  
         [0079]    Subsequently, one surface of the porous member  64  is bonded to one surface of a filter member by an adhesive, or the like, to form a two-layer structure, which is then folded at a longitudinally middle portion thereof with one half of the porous member  64  facing the other half, thereby to form a four-layer structure. Thus, the upper filter member  61   a  and the lower filter member  61   b  are formed. Then, the peripheral portions  15  of the upper filter member  61   a  and lower filter member  61   b  except the folded portion thereof are welded onto a peripheral portion of the porous member  64  by thermal welding means, such as ultrasonic welding or electrodeposition, while force is being applied from the upper and lower sides of the filter members  61   a,    61   b.  In this manner, the porous member  64  fills the inner space between the upper filter member  61   a  and lower filter member  61   b,  to thus form fuel paths in the filter  60 . In addition, an opening  11   b  is formed in a substantially middle portion of the folded portion of the two-layer structure consisting of the filter member and the porous member  64 , such that an end portion of the coupling member  63  is inserted into the opening  11   b.    
         [0080]    In the sixth embodiment as described above, the peripheral portion of the porous member  64  except the folded portion thereof is formed simultaneously with the peripheral portions of the upper filter member  61   a  and the lower filter member  61   b  through the thermal welding means. However, the porous member  64  may be initially formed into a shape corresponding to the shape of the inner space of the filter  60 , and the peripheral portions  15  of the upper filter member  61   a  and lower filter member  61   b  may be welded together by thermal welding means, such as ultrasonic welding or electrodeposition, after the two-layer structure of the filter member and the porous member  64  is folded at a central portion thereof.  
         [0081]    The coupling member  63  consists of a pipe-like member  63   f  having a flange  63   b  formed around a lower portion of the member  63   f.  The coupling member  63  and the two-layer structure of the filter member and the porous member  64  are integrated with each other by aligning a hollow portion of the pipe-like member  63   f  with the opening  11   b  of the folded portion of the two-layer structure, and fixing the lower end face of the flange  63   b  to the outer surface of the folded portion by an adhesive, or the like. With this arrangement, the fuel pump disposed within the fuel tank can be located in the vicinity of the inner wall of the fuel tank.  
         [0082]    While the fuel filter  60  has a generally rectangular shape in this embodiment, the filter may have any other shape provided that the folded portion is formed straight.