Abstract:
A fuel filter of an internal combustion engine including a filter housing having a lowermost housing base and a topmost removable housing lid. The filter housing has one raw fuel inlet and one pure fuel outlet. A replaceable annular filter insert mounts there in the filter housing, fuel flowing through it from outside towards inside. The filter subdivides an interior space of the filter housing into a raw zone and a pure zone. A supporting body is arranged in the interior of the annular filter insert, a first flow channel and a second flow channel extending therethrough. The first flow channel connects at one end to the pure zone and at the other end to the pure fuel outlet. The second flow channel connects at one end to the raw zone via a vent throttle or a vent valve and at the other end to a reservoir return in the filter housing. The raw fuel inlet is in the housing base and a flow channel leads from the raw fuel inlet to a portion of the raw zone of the interior space of the filter housing which is, during operation, topmost.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    This invention relates to a fuel filter of an internal combustion engine, in particular of a diesel engine, with a filter housing having an operationally lower housing base and an upper, removable housing cover, with one raw fuel inlet and pure fuel outlet each being provided in the filter housing, with a replaceable ring filter insert being arranged in the filter housing through which the fuel can flow radially from the outside to the inside, said ring filter insert subdividing an interior of the filter housing into a raw area and a pure area, with a support body being arranged in the interior of the ring filter insert through which extends a first flow channel being connected, on the one hand, with the pure area and, on the other hand, with the pure fuel outlet, and a second flow channel being connected, on the one hand, with the raw area via a vent throttle or a vent valve and, on the other hand, with a tank return in the filter housing. 
         [0002]    A fuel filter of the aforementioned type is known from DE 60 2004 006 277 T2. With this fuel filter, the raw fuel inlet is provided either on the bottom at the circumference or at the lower end wall of the filter housing. With this fuel filter, the support body is designed in two parts, with a radially outer part of the support body forming one part of the filter insert and a radially inner part of the support body forming one part of the filter housing. The fuel to be cleaned flows from the bottom to the top around the outer circumference of the filter insert and then flows through the filter insert radially from the outside to the inside. The cleaned fuel flows near the upper end of the support body into its central flow channel and through it to the pure fuel outlet. For venting the filter housing, a vent throttle is used in an upper end disk of the ring filter insert, with the raw area of the housing being in flow connection with the second flow channel via the vent throttle. On the other hand, the second flow channel in the support body is in flow connection with a tank return. 
         [0003]    It is to be considered disadvantageous with this known fuel filter that the separation of water droplets entrained in the fuel is rendered more difficult due to the flow of the fuel to be cleaned from the bottom to the top at the outer circumference of the filter insert. 
         [0004]    Another fuel filter is known from the document U.S. Pat. No. 5,922,199 A. This fuel filter is designed as a hanging cup system, wherein a cup-shaped housing is screwed as a bottom part onto a base here forming the upper part of the fuel filter. Maintenance of the fuel filter is here only possible from the bottom by unscrewing the hanging cup. In this case, fuel disadvantageously always remains in the cup which may easily result in pollution and renders it difficult to change the filter insert. 
       SUMMARY OF THE INVENTION 
       [0005]    The present invention accordingly has the object of providing a fuel filter of the initially indicated type which avoids the aforementioned disadvantages and in which in particular a favorable arrangement of the raw fuel inlet is rendered possible and in which the separation of water droplets from the fuel is encouraged. 
         [0006]    According to the invention, this problem is solved with a fuel filter of the initially indicated type which is characterized in that the raw fuel inlet is arranged in the housing base of the filter housing and that, in or on the fuel filter, a flow channel is provided extending from the raw fuel inlet to an operationally upper part of the raw area of the interior of the filter housing. 
         [0007]    The arrangement according to the invention of the raw fuel inlet in the housing base provides an advantageous arrangement which does not impair maintenance of the fuel filter from the top. By passing the fuel in the upper part of the raw area of the housing interior, a fuel flow direction from top to bottom results on the outer circumference of the filter insert which encourages the separation and deposit of water droplets from the fuel in a lower area of the filter housing. 
         [0008]    A preferred development of the invention provides that the flow channel leading from the raw fuel inlet to the operationally upper part of the raw area extends as a third flow channel through the support body. With this embodiment, three flow channels are advantageously passed through the support body, thereby achieving a high level of integration of functions with few individual parts. 
         [0009]    To enable a stable design of the support body with flow channels having the lowest possible resistance, it is proposed that one of the three flow channels extends concentrically in the support body and that the two other flow channels extend eccentrically and in circumferential direction of the support body spaced apart from each other in it. 
         [0010]    Another advantageous embodiment provides that the flow channel concentrically extending in the support body is the second flow channel connected with the tank return and is used for venting, and that the vent throttle or the vent valve is designed or arranged at one upper end of the support body in a wall of the support body separating the raw area from the second flow channel. With this embodiment, the vent throttle or the vent valve comes to lie at a point as far up top as possible in the filter housing so that virtually complete venting of the housing is ensured. 
         [0011]    For a simple and fast mechanical and flow-specific connection of the fuel filter with the associated internal combustion engine, it is advantageous if, in addition to the raw fuel inlet, the pure fuel outlet and the tank return are arranged in the housing base of the filter housing and flange and/or line connections are provided on the housing base for the raw fuel inlet, the pure fuel outlet and the tank return. 
         [0012]    For the purpose of the simplest possible installation of the fuel filter, it is advantageous that preferably the support body is mechanically connected on its lower end with the housing base and in terms of flow with the raw fuel inlet, the pure fuel outlet and the tank return. 
         [0013]    A particularly advantageous connection, also disconnectable if necessary, is realized such that the housing base and the support body are preferably provided with interacting threads for their connection with each other and that the threads are designed such that, in screwed together condition, the support body assumes relative to the housing base in circumferential direction a defined screwing end position angularly aligned for the flow-specific connection with the raw fuel inlet, the pure fuel outlet and the tank return. 
         [0014]    Since fuel filters according to the invention are a mass product, it is essential that they can be produced economically in large quantities. A contribution to this objective will be that preferably the support body with the three flow channels extending therein is a one-piece plastic injection molding or a one-piece light metal casting. 
         [0015]    To prevent that water separated from the raw fuel impairs the filter function or gets into the pure fuel, the invention proposes that the housing base is designed or connected with a water collection chamber forming, during operation, a lowest part of the fuel filter. To this end, a water collection cup can be built on, e.g. screwed on, to the bottom of the filter housing. 
         [0016]    Finally, it is also provided according to the invention that the housing cover and the ring filter insert are connected with each other via a detachable latching connection transmitting axial tensile forces and that, by a movement of the housing cover together with the ring filter insert relative to the filter housing and the support body, a direct flow connection is upwardly releasable from the raw area to the tank return. This is to achieve that, upon maintenance of the fuel filter, a removal of the housing cover can lift off the filter insert together with the cover. Simultaneously, it is provided that fuel present in the filter housing is discharged from the housing through the tank return. Upon its removal from the filter housing, the filter insert is then virtually free of fuel and any pollution will thus be prevented. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0017]    In the following, an exemplary embodiment of the invention is explained by means of a drawing. In the Figures of the drawing: 
           [0018]      FIG. 1  shows a fuel filter with closed housing, in a longitudinal section; 
           [0019]      FIG. 2  shows the fuel filter of  FIG. 1  with opened housing and removed filter insert, in a top view; 
           [0020]      FIG. 3  shows the fuel filter in a cross-section at the level of a housing base of the filter housing; 
           [0021]      FIG. 4  shows a support body as part of the fuel filter, in a perspective view inclined from the bottom; 
           [0022]      FIG. 5  shows the support body from  FIG. 4  in a side view; 
           [0023]      FIG. 6  shows the support body from  FIG. 4  and  FIG. 5  in a view from the bottom; 
           [0024]      FIG. 7  shows the support body from  FIGS. 4 to 6  in a longitudinal section; 
           [0025]      FIG. 8  shows the fuel filter in a partial longitudinal section with inserted filter insert; and 
           [0026]      FIG. 9  shows the fuel filter from  FIG. 8  while the filter insert is removed, in the same presentation as in  FIG. 8 . 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0027]      FIG. 1  shows a fuel filter  1  in longitudinal section. The fuel filter  1  has a filter housing  10  with a housing base  11  and a topside housing cover  12 . A ring filter insert  3  is arranged in the filter housing  10 . On the inside of the ring filter insert  3 , a support body  2  is provided which is connected on its bottom end with the housing base  11 , here screwed. The lowermost part of the filter housing  10  is formed by a water collection cup  4  forming a water collection chamber  40 . 
         [0028]    On its outer circumference, the support body  2  has a plurality of support ribs  20  protecting a filter media body  30  of the ring filter insert  3  from collapsing. Altogether three flow channels  21 ,  22  and  23  extend on the inside of the support body  2 . The first flow channel  21  is used to pass pure fuel from a pure area  10 . 2  of the housing  10  to a pure fuel outlet  14 . The second flow channel  22  in the center of the support body  2  is used to vent the filter housing  10 . To this end, the upper end  24  of the support body  2  is closed except for a vent throttle  25 . On the lower end, the second flow channel  22  is in flow connection with a tank return  15 . The third flow channel  23  is used to pass raw fuel from a raw fuel inlet  13  into an upper part of the raw area  10 . 1  of the filter housing  10 . 
         [0029]    The ring filter insert  3  consists of a hollow cylindrical filter media body  30  which is bordered on the top by an upper end disk  31 . 1  and on the bottom by a lower end disk  31 . 2 . Arranged on the upper end disk  31 . 1  is a radial seal  32 . 1  which seals against an upper ring area  26  of the support body  2 . Under the lower end disk  31 . 2 , another radial seal  32 . 2  is arranged which seals off against a lower end of the support body  2  as well as an area of the housing base  11  bearing the support body  2 . 
         [0030]    The support body  2  screwed together with the housing base  11  is sealed with two axial seals  27 . 1  and  27 . 2  against the base  11 . Threads  18  and  28  are used for screwing. Thread  18  is arranged on the upper end of a support body screw neck  16  and the thread  28  is an internal thread in the lower end area of the second flow channel  22  of the support body  2 . The support body screw neck  16  is inserted from the bottom into a suitable opening in the base  11  and has an enlarged head  17  forming a stop. 
         [0031]    The raw fuel inlet  13  and the pure fuel outlet  14  extend perpendicularly to the drawing planes of  FIG. 1  from the cutting plane towards the front so that they are visible only for a small part. The raw fuel inlet  13  is usually connected via a fuel line with an active fuel pump to the associated fuel tank. The pure fuel outlet  14  usually leads via another line to a fuel injection system of the associated internal combustion engine. The tank return  15  extends from the center of the housing base  11  to the left. Through a connection line not shown, the tank return  15  is connected with the fuel tank of the associated internal combustion engine. 
         [0032]    The housing cover  12  is screwed with the filter housing  10  and can be unscrewed for maintenance of the fuel filter  1 . On the inside of the housing cover  12 , a detachable latching connection  33  is arranged between that and the ring filter insert  3  which is able to transmit axial tensile forces from the housing cover  12  to the ring filter insert  3  which are large enough to pull off the ring filter insert  3  from the housing base  11  and the support body  2 . 
         [0033]    During operation of the fuel filter  1 , raw fuel flows through the raw fuel inlet  13  into the third flow channel  23  of the support body  2  and in it to the top where the raw fuel exits from the support body  2  in the raw area  10 . 1  of the filter housing  10 . From the raw area  10 . 1 , fuel flows through the filter media body  30  of the ring filter insert  3  in radial direction from the outside to the inside and then gets into the pure area  10 . 2 . In the pure area  10 . 2 , the now filtered fuel flows upwardly and there enters into the first flow channel  21  of the support body  2 . In flow channel  21 , the filtered fuel flows downwardly to the pure fuel outlet  14 . 
         [0034]    Due to feeding raw fuel into the upper part of the raw area  10 . 1 , a downward flow of the fuel results in the interior of the filter housing  10  on the outer circumference of the filter media body  30 . This direction of flow encourages the separation of entrained water droplets from the raw fuel and their deposit in the water collection chamber  40 . 
         [0035]    Dirt particles entrained in the raw fuel are separated and collected in the filter media body  30 . Water droplets contained in raw fuel collect on the filter media body  30  and, upon reaching a certain size, they trickle down from it and sink to the bottom in the fuel due to their higher density and thus get into the water collection chamber  40 . The water collection chamber  40  in the water collection cup  4  can be automatically drained as needed, in a manner known per se, via a corresponding water drain valve not shown here. 
         [0036]      FIG. 2  shows the filter housing  10  of the fuel filter from  FIG. 1  in a top view with the housing cover  12  removed and with the ring filter insert  3  taken from the filter housing  10 . In the center of  FIG. 2 , the tank return  15  can be seen which continues towards the left to the outside of the housing  10 . In  FIG. 2 , the raw fuel inlet  13  extends from bottom to top, i.e. radially from the outside to the inside; in reverse, the pure fuel outlet  14  extends parallel thereto. The support body screw neck  16  is visible around the central tank return  15 . The housing base  11  lies in the background of  FIG. 2 . 
         [0037]      FIG. 3  shows the filter housing in a cross section through the housing base  11 . In this respect, the cut runs through the raw fuel inlet  13 , the pure fuel outlet  14  and through the tank return  15 . In the center of the housing base  11 , the support body screw neck  16  is visible through which extends a section of the tank return  15 . 
         [0038]    In  FIG. 4 , the support body  2  as a part of the fuel filter  1  is presented by itself in a perspective view at an incline from below. Support ribs  20  are visible on the outer circumference of the support body  2 . On the lower end of the support body  2 , its front face with flow channels  21 ,  22  and  23  is visible. A sealing groove  27 . 1 ′ extends around the first flow channel  21 , and another sealing groove  27 . 2 ′ extends around the third flow channel  23 . In the center of the support body  2 , its thread  28  for the connection with the housing base  11  is visible. On the upper end of the support body  2 , its upper ring area  26  is located. 
         [0039]      FIG. 5  shows the support body  2  again as an individual part, now in a side view. The first flow channel  21  extends on the left in the support body  2 , in its longitudinal direction. The second flow channel  22  extends centrally through the support body  2 . The third flow channel  23  extends on the right of the support body  2  in longitudinal direction. The support ribs  20  extend around the flow channels  21 ,  22  and  23  in the form of spirals. The upper termination of the support body  2  is its upper end  24 . Below that is the upper ring area  26  of the support body  2  which serves as the sealing rest of the ring filter insert  3 . 
         [0040]      FIG. 6  shows the support body  2  in a view onto its underside. In the center of  FIG. 6 , the view extends through the central, second flow channel  22  up to the vent throttle  25  at the upper end of the support body  2 . The first flow channel  21  lies on the left of flow channel  23 . The third flow channel  23  lies on the right of the central flow channel  22 . The sealing groove  27 . 1 ′ runs around the flow channel  21 . The sealing groove  27 . 2 ′ runs around the flow channel  23 . 
         [0041]    As illustrated in a joint view of  FIGS. 2 and 6 , the central area of the base  11  and the lower front end of the support body  2  are geometrically coordinated such and adjusted to each other that—with the support body  2  firmly screwed together with the housing base  11 —the flow channels  21  and  23  are lined up with the pure fuel outlet  14  and the raw fuel inlet  13 . To this end, the aforementioned threads  18  and  28  are arranged such that, upon screwing the support body  2  to the housing base  11 , an end position of the screwing defined in circumferential direction results in which the overlap required for the flow connections is realized. 
         [0042]      FIG. 7  shows the support body  2  in a longitudinal section. Support ribs  20  are here also visible radially outside. The second flow channel  22  extends centrally through the support body  2 . The first flow channel  21  is visible on the left thereof. The third flow channel  23  extends on the right from the central flow channel  22 . The two sealing grooves  27 . 1 ′ and  27 . 2 ′ are visible on the lower end of the support body  2 . Thread  28  is visible in the lower end area of the central, second flow channel  22 . The central, second flow channel  22  is closed towards the top by the upper end  24  of the support body  2  with the exception of the vent throttle  25  there attached. In addition, the upper ring area  26  is visible in the upper end area of the support body  2 . 
         [0043]    It is evident on the basis of  FIGS. 4 to 7  that, despite its relatively complicated form and the three flow channels  21  to  23  extending therein, the support body  2  can be advantageously produced by injection molding as a one-piece component. The support body can be removed from the mold in two radial directions opposite each other and in two axial directions opposite each other. 
         [0044]    As already mentioned above in connection with  FIG. 1 , the latching connection  33  exists between the housing cover  12  and the ring filter insert  3 . Its purpose is explained in the following on the basis of  FIGS. 8 and 9 . 
         [0045]    In the longitudinal section,  FIG. 8  presents a segment of the fuel filter  1  at the level of the housing base  11  and the lower part of the ring filter insert  3 , the cutting plane here being rotated by 90° versus  FIG. 1 . In  FIG. 8 , the ring filter insert  3  is completely inserted into the filter housing  10  and sits, on the one hand, with its lower part on the lower end area of the support body  2  and, on the other hand, on the central part of the base  11  facing it. The radial sealing ring  32 . 2  is arranged between the lower end disk  31 . 2  of the ring filter insert  3 , on the one hand, and the support body  2  as well as the housing base  11 , on the other hand. In the built-in condition of the ring filter insert  3 , the radial sealing ring  33 . 2  covers up—due to its adequate height in axial direction—an annular gap between the lower end of the support body  2  and the housing base  11 . This annular gap covered up in the condition according to  FIG. 8  is in flow connection with the tank return  15 . 
         [0046]    In the same presentation as  FIG. 8 ,  FIG. 9  shows the ring filter insert  3  during its removal from the filter housing  10 . This removal is effected by unscrewing the housing cover  12  carrying along the ring filter insert  3  via the latching connection  33 . Due to the movement of the ring filter insert  3  towards the top, the lower end disk  31 . 2  with the radial sealing ring  32 . 2  is also moved upwardly and thus recedes from the transition area or annular gap between the lower end of the support body  2  and the upper side of the central part of the housing base  11 . The raw area  10 . 1  of the filter housing  10  thereby realizes a flow connection with the tank return  15 . In this way, already while twisting off the housing cover  12 , fuel from the filter housing  10  can flow off through the tank return  15  into the fuel tank so that, with opened filter housing  10 , the ring filter insert  3  can be removed virtually fuel-free. 
         [0047]    As is apparent from the foregoing specification, the invention is susceptible of being embodied with various alterations and modifications which may differ particularly from those that have been described in the preceding specification and description. It should be understood that I wish to embody within the scope of the patent warranted hereon all such modifications as reasonably and properly come within the scope of my contribution to the art. 
         [0000]    
       
         
               
             
               
               
               
             
           
               
                   
               
               
                 List of reference symbols: 
               
             
          
           
               
                   
                 Symbol 
                 Designation 
               
               
                   
                   
               
               
                   
                  1 
                 Fuel filter 
               
               
                   
                 10 
                 Filter housing 
               
               
                   
                 10.1 
                 Raw area 
               
               
                   
                 10.2 
                 Pure area 
               
               
                   
                 11 
                 Housing base 
               
               
                   
                 12 
                 Housing cover 
               
               
                   
                 13 
                 Raw fuel inlet 
               
               
                   
                 14 
                 Pure fuel outlet 
               
               
                   
                 15 
                 Tank return 
               
               
                   
                 16 
                 Support body screw neck 
               
               
                   
                 17 
                 Head of 16 
               
               
                   
                 18 
                 Thread on 16 
               
               
                   
                  2 
                 Support body 
               
               
                   
                 20 
                 Support ribs 
               
               
                   
                 21 
                 First flow channel 
               
               
                   
                 22 
                 Second flow channel 
               
               
                   
                 23 
                 Third flow channel 
               
               
                   
                 24 
                 Upper end of 2 
               
               
                   
                 25 
                 Vent throttle 
               
               
                   
                 26 
                 Upper ring area 
               
               
                   
                 27.1, 27.2 
                 Seals 
               
               
                   
                 27.1′, 27.2′ 
                 Sealing grooves 
               
               
                   
                 28 
                 Thread on 2 
               
               
                   
                  3 
                 Ring filter insert 
               
               
                   
                 30 
                 Filter media body 
               
               
                   
                 31.1 
                 Upper end disk 
               
               
                   
                 31.2 
                 Lower end disk 
               
               
                   
                 32.1 
                 Seal on 31.1 
               
               
                   
                 32.2 
                 Seal on 31.2 
               
               
                   
                 33 
                 Latching connection between 12 and 3 
               
               
                   
                  4 
                 Water collection cup 
               
               
                   
                 40 
                 Water collection chamber