Abstract:
The present invention relates to a fuel filter having a filter element and connections for the fuel inlet and the fuel outlet. In order to permit a more compact design, the fuel filter employs flat, block-shaped filter element.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a 35 USC 371 application of PCT/DE 2004/001574 filed on Jul. 20, 2004. 
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a fuel filter with at least one filter element and connections for the fuel supply and fuel outlet. 
     2. Description of the Prior Art 
     A fuel filter of the type with which this invention is concerned, known from DE 198 11 689 A1 has a housing made of solid plastic and has a beaker-shaped bottom part and a lid-like top part that is detachably fastened to the beaker-shaped bottom part by means of a quick release. The beaker-shaped bottom housing part contains a hollow, cylindrical star filter that rests on a pedestal section. The pedestal section contains a sump for water separated out during filtration of the fuel and a water drain that can be closed by means of a screw plug. In addition, the pedestal region is provided with a fuel inlet that feeds into an inlet duct for a heating unit welded in place beneath the pedestal section. The pedestal section is also provided with an outlet duct that allows the fuel to travel from the heating unit to the dirty side of the filter. The flow passes through the filter insert radially from the outside to the inside. Its clean side is connected to an outlet fitting via which the cleaned fuel can be drained off in the direction of the engine via a first duct. In addition, the outlet fitting is provided with a second duct, which can be closed by an overflow valve and permits the fuel to be returned to the tank. The clean side of the filter is also connected to the sump. 
     Fuel filters of this kind are used, among other things, in the engines of motor vehicles. 
     One problem of these previously known filters is that they are comparatively bulky and are difficult to integrate into the engine compartment of a vehicle. 
     In this respect, the object of the present invention is to develop a fuel filter that permits a compact design. This object is attained with a fuel filter of the type mentioned at the beginning in that the filter element is embodied as flat. 
     A surprising discovery has been made that instead of star filter inserts, it is possible to use flat filter elements in which the clean side and the dirty side are situated essentially parallel to each other. This makes it possible to embody the fuel filter as a whole as flat and for it therefore to be significantly flatter than would be possible with the use of star filter inserts, while providing the same through flow capacity. This yields a significantly greater possibly structural variety, thus allowing the form of the fuel filter to be better adapted to the space available in the engine compartment. 
     The folding of the filter material advantageously produces a block-like or box-shaped filter element with a good stability and a large surface area. 
     In a preferred embodiment form of the present invention, the clean side of the filter element is encapsulated and connected to the fuel outlet. An encapsulation of this kind can, for example, be comprised of caps for covering the top side and the upper and lower ends of the filter element, and a side wall encompassing the clean side of the filter element, each made of plastic. A filter element embodied in this way can easily be inserted into a fuel filter housing without requiring an additional seal between the clean side of the filter element and its dirty side. Additional structural features and components inside the housing for dividing the clean side from the dirty side are thus rendered superfluous; the dirty side of the filter can encompass the encapsulated filter element as completely as possible. 
     In addition or conversely, the dirty side of the filter element can be correspondingly encapsulated and connected to the fuel inlet. 
     In another embodiment of the fuel filter according to the present invention, two or more filter elements are provided, which can be situated for example adjacent to each other at their upper, lower, or lateral sides, and essentially in a single plane, but can also be situated in planes extending at an angle to each other. 
     In an additional preferred embodiment of the present invention, the fuel inlet and the fuel outlet are situated at one end of the fuel filter or at opposite ends of the fuel filter. This makes it possible to assure that the advantage of a flat design is not canceled out by connections protruding beyond the fuel filter. 
     In another preferred embodiment, the flow entry of the fuel into the fuel filter housing is designed to reduce or eliminate turbulence in the region of the bottom of the fuel filter, particularly when it is horizontally oriented. It has turned out to be particularly effective to use a flow baffle in the region of the fuel inlet, which is preferably inclined upward and thus deflects the flow toward the top of the fuel filter housing. 
     The inlet distribution stabilizer advantageously provides for particularly favorable filtration properties of the fuel filter while requiring a remarkably low overall volume of the fuel filter. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The present invention will be explained in greater detail below, in conjunction with drawings, in which: 
         FIG. 1  is a perspective view of a first exemplary embodiment of the fuel filter according to the present invention, 
         FIG. 2  shows a top plan view of the fuel filter shown in  FIG. 1 , 
         FIG. 3  shows the fuel filter in a section along the cutting line A-A according to  FIG. 2 , 
         FIG. 4  shows the fuel filter in a section along the cutting line B-B according to  FIG. 2 , 
         FIG. 5  is a perspective view of a second embodiment form of the fuel filter according to the present invention, 
         FIG. 6  shows an end view of a third exemplary embodiment of the fuel filter according to the present invention, 
         FIG. 7  shows a view of the opposite end from the one shown in  FIG. 6 , 
         FIG. 8  shows a cross section through the fuel filter of the third exemplary embodiment, 
         FIG. 9  shows a longitudinal section through the fuel filter along the plane labeled IX-IX in  FIG. 6 , 
         FIG. 10  shows a longitudinal section through the fuel filter along a plane labeled X-X in  FIG. 7 , and 
         FIG. 11  shows a longitudinal section through the fuel filter along the cutting plane labeled XI-XI in  FIG. 7 . 
     
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     The proposed fuel filter is particularly well suited for filtering fuel, particularly diesel fuel, in a fuel supply of an internal combustion engine of a motor vehicle. 
       FIGS. 1 through 4  show various views of and sections through a first, preferred, selected, particularly advantageous exemplary embodiment of a flat fuel filter  1 . 
     In all of the figures, parts that are the same or function in the same manner have been provided with the same reference numerals. Provided that nothing to the contrary is mentioned or depicted in the drawings, that which is mentioned in conjunction with and shown in one of the figures applies to all of the figures and all of the exemplary embodiments. As long as nothing to the contrary is stated in the explanations, the features of the different exemplary embodiments can be combined with one another. 
       FIGS. 1 through 4  show the flat fuel filter  1  in an essentially horizontal orientation. The fuel filter  1  has a filter housing  2 . The filter housing  2  has an upper side wall  2   a , a lower side wall  2   b , a first side longitudinal wall  2   c  and parallel to it, a second side longitudinal wall  2   d , a first end  2   e , and an opposite second end  2   f  oriented toward the cover. The filter housing  2  is essentially comprised of a housing part  3   a  and a cover  3   f . The housing part  3   a  is essentially the shape of a block-like or box-shaped beaker and essentially comprises the sides  2   a ,  2   b ,  2   c ,  2   d , and  2   e  of the filter housing  2 . At the end  2   f  of the filter housing  2 , the housing part  3   a  is closed by a cover  3   f.    
     The filter housing  2  has an elongated, flat form whose front end  2   f  is closed by the cover  3   f . The outside of the cover  3   f  is provided with a connection  4  for the fuel inlet, an electrical connection  5  for a heating unit, and an electrical connection  6  for a temperature sensor. On the underside of the filter housing  2 , or more precisely, on the lower side wall  2   b , a water outlet  7  is provided toward the end  2   f  closed by the cover  3   f . The end  2   e  of the housing part  3   a  of the filter housing  2  oriented away from the cover  3   f  is provided with a connection  8  for the fuel outlet. 
     The filter housing  2  is more than twice as wide and more than three times as long as it is high. The filter housing  2 , at least in a rough sense, has an approximately block-like or box-shaped form. 
     As is particularly clear in  FIGS. 2 and 3 , the connection  8  for the fuel outlet extends in a plane that is parallel to the longitudinal axis, and the connection  4  for the fuel inlet extends in a plane extending parallel to this, close to the longitudinal wall  2   c  of the filter housing  2 . 
     As can be surmised from the sectional views in  FIGS. 3 and 4 , the filter housing  2  contains a horizontally extending filter insert with a filter element  11 . The filter element  11  is flat. The filter element  11  is block-shaped. The filter element  11  therefore fits into the block-shaped filter housing  2  with ease. The top of the filter element  11  is completely encapsulated by a wall  12 ; together with the filter element  11 , the wall  12  encloses a clean side  13  of the fuel filter. The clean side  13  is essentially above the filter element  11 , between the filter element  11  and the wall  12 . The clean side  13  is connected via a duct segment  14  to the connection  8  for the fuel outlet. The filter element  11  is inserted inside the filter housing  2  in guide rails  15  provided on the side walls. 
     The filter element  11  and the wall  12  together constitute a filter insert. The space in the filter housing  2  surrounding the entire filter insert serves as the dirty side of the filter  1 . The fuel flows from bottom to top through the filter element  11 , from the dirty side to the clean side  13 . 
     Whereas the wall  12  rests against the upper side wall  2   a  of the filter housing  2  over large regions, in the region of the connection  4  for the fuel inlet, a gap  16  extends in the longitudinal direction of the filter housing  2 , between the wall  12  and the upper side wall  2   a  of the filter housing  2 . In the region of the connection  4  for the fuel inlet, a flow baffle  17  is provided, which deflects the fuel entering the filter housing  2  into this gap  16  so that the fuel is distributed from there into the filter housing  2 . This significantly reduces the flow velocity of the fuel and prevents turbulence, particularly in the bottom region  18  of the filter housing  2 . 
     Between the wall  12  and the upper side wall  2   a  grooves can be provided, which extend longitudinally and/or transversely and/or on an incline and/or diagonally. Part or all of the grooves can be let into the wall  12  and/or the upper side wall  2   a . The grooves are part of the gap  16 . The selected exemplary embodiment has a number of parallel longitudinal grooves  161  and parallel transverse grooves  16   q  in the side of the wall  12  oriented toward the side wall  2   a . The longitudinal grooves  16   l  and the transverse grooves  16   q  extend at approximately right angles to one another. These grooves can improve the uniform distribution of fuel over the width of the filter. 
     The lower side wall  2   b  of the filter housing  2  slopes down toward the water outlet  7  and thus constitutes a sump for water that is separated out on the dirty side of filter element  11  and collects in the region of the water outlet  7  due to its higher specific weight. 
     In the fuel filter  1  according to the present invention, the cover  3   f  of the filter housing  2  is attached to the housing part  3   a  of the filter housing  2  in a snug, sealed, and nondetachable manner. The housing part  3   a  and the cover  3   f  can, for example, be comprised of metal or plastic. Depending on the material of the housing part  3   a  and cover  3   f , these parts are attached to each other, for example, by means of welding, ultrasound welding, vibration welding, friction welding, the application of heat, or crimping. It is also possible, however, to attach the cover  3   f  to the housing part  3   a  in a sealed, but detachable fashion so that the filter element  11  in the filter housing  2  can be replaced as needed. 
     This fuel filter  1  is particularly suited for horizontal installation in a motor vehicle. 
       FIG. 5  shows a similar fuel filter  20 , which differs from the above-described fuel filter  1  in that it is designed for vertical use; all of the connections  21 ,  22 ,  23  for the fuel inlet and for the fuel outlet as well as the electrical connections  24 ,  25  for a heating unit and a temperature sensor are provided on the upper end of the filter housing  27 , which end is embodied in the form of a cover  26 . One of the connections  22 ,  23  for the fuel outlet serves as a fuel return to the tank and is connected to an overflow valve on the inside of the cover  26 . 
     The bottom is merely provided with a water outlet  28  and a connection  29  for a water level sensor for detecting the water level inside the housing. 
       FIGS. 6 through 11  show different views of and sections through another, preferred, selected, particularly advantageous exemplary embodiment of a flat fuel filter  31 . 
     As shown in  FIG. 7 , the fuel filter  31  has an essentially approximately rectangular end  2   e  and, as shown in  FIG. 6 , an essentially approximately rectangular end  2   f . In order to insert the filter element  11  into the filter housing  2 , the housing part  3   a  is initially open at the end  2   f  shown in  FIG. 6  and is then closed with the cover  3   f  during subsequent assembly of the fuel filter  31 . 
     The connection  4  for the fuel inlet is provided on the cover  3   f . The cover  3   f  also has the electrical connection  5  for the heating unit  35 , the electrical connection  6  for the temperature sensor  36 , and the electrical connection  29  for the water level sensor. The flat lower side wall  2   b  of the fuel filter  31  accommodates the water outlet  7 , which can be opened as needed. 
     As shown in  FIG. 7 , the end  2   e  of the filter housing  2  oriented away from the cover end  2   f  has two connections  8   a  and  8   b . Both of the connections  8   a  and  8   b  serve as fuel outlets. During normal operation of the fuel filter  31 , the filtered fuel only comes out of one of two connections  8   a  or  8   b . However, if the pressure in the filter housing  2  were to climb excessively due to excessive soiling, then an overflow valve inside the filter housing  2  would open, permitting the fuel to bypass the filter element  11  and flow out of the filter housing  2 . 
     While the fuel filter is being used, fuel first travels through the cover  3   f  via the connection  4  serving as the fuel inlet, into an insert  33  provided in the filter housing  2 , in the region of the cover  3   f . In the region of the connection  4  serving as the fuel inlet, the insert  33  constitutes a cavity that accommodates, for example, a heating unit  35  and a temperature sensor  36 . The heating unit  35  is electrically connected by means of the electrical connection  5  and the temperature sensor  36  is electrically connected by means of the electrical connection  6 . Inside the insert  33 , the fuel is agitated so as to assure a favorable transmission of heat between the heating unit  35  and the fuel on the one hand and between the fuel and the temperature sensor  36  on the other. 
     From the inside of the insert  33 , the fuel travels through an opening  38  ( FIG. 10 ) into the gap  16 . A number of openings  38  can be provided one after the other in the horizontal direction or the opening  38  can be embodied in the form of a horizontally extending elongated hole. The gap  16  has a number of sections: an upper gap region  16   a , two lateral gap regions  16   c  and  16   d  ( FIG. 8 ), and an end gap region  16   e  ( FIG. 9 ). First, the fuel flows through the opening  38  into the upper gap region  16   a . The upper gap region  16   a  extends over nearly the entire length and width of the filter housing  2 . In the region of the side longitudinal wall  2   c , the first lateral gap region  16   c  connects the upper gap region  16   a  to the bottom region  18 . In the region of the side longitudinal wall  2   d , the second lateral gap region  16   d  connects the upper gap region  16   a  to the bottom region  18 . In the region of the end  2   e , the end gap region  16   e  connects the upper gap region  16   a  to the bottom region  18 . If need be, the gap region  16   e  can be omitted and/or a gap, not shown, can be provided in the region of the end  2   f , along the insert  33 , which connects the upper gap region  16   a  to the bottom region  18 . The gap regions  16   a ,  16   c ,  16   d ,  16   e  convey the fuel around the filter element  11  into the bottom region  18 . The distribution of the gaps  16   c ,  16   d , and  16   e  uniformly distributes the fuel from the upper gap region  16   a  to the bottom region  18 . The wall  12  prevents fuel from reaching the filter element  11  directly, instead forcing the fuel to spread out over essentially the entire length of the block-like fuel filter  31 . 
     In all of the selected exemplary embodiments, longitudinal grooves  16   l  and transverse grooves  16   q  or other grooves can be provided in the gap  16 , preferably in the upper gap region  16   a , as explained above in connection with the first exemplary embodiment. Corresponding fuel-distributing grooves can also be provided in the lateral and end gap regions  16   c ,  16   d ,  16   e.    
     The guide rails  15  between the filter element  11  and the filter housing  2  are short and interrupted at several points so that the guide rails  15  represent practically no hindrance to the flow of fuel through the gaps. 
     Distributed uniformly over the entire length of the gap region  16   a , the fuel branches out from the upper gap region  16   a  into the lateral gap regions  16   c ,  16   d , and  16   e . In these lateral regions, the fuel flows between the filter housing  2  and the wall  12  enclosing the filter element  11  therein, into the bottom region  18  underneath the filter element  11 . 
     The cross section of the bottom region  18  underneath the filter element  11  is significantly greater than the cross section of the gap  16 . The relatively narrow gap  16  with the regions  16   a ,  16   c ,  16   d , and  16   e  forces the fuel to flow into the bottom region  18  distributed uniformly over the entire length of the fuel filter  31 . As a result, fuel flows to every region of the filter element  11  with practically the same intensity. This makes it possible to favorably exploit the entire volume of the filter element  11 . 
     The relatively large cross section of the bottom region  18  encourages the separation of water in the fuel filter  31 . 
     Because the bottom region  18  has a relatively large cross section, the fuel settles in the bottom region  18  and, without excessive turbulence, can flow from the bottom region  18 , through the filter element  11  from bottom to top, into a cavity  39 . The cavity  39  extends above the filter element  11  between the filter element  11  and the wall  12 , practically over the entire length and width of the filter element  11 . The cavity  39  is part of the clean side  13  of the fuel filter  31 . 
     The fuel travels from the cavity  39  through a passage  42   a  to the connection  8   a  or through a passage  42   b  to the connection  8   b.    
     The gap  16  and the bottom region  18  are series connected and matched to each other so that these parts inside the filter housing  2  combine to constitute a particularly effective inlet distribution stabilizer  30 . In the selected exemplary embodiments, the gap  16  has the regions  16   a ,  16   b ,  16   d ,  16   e  and grooves  16   l  and  16   q  that are matched to one another. The cross section of the gap  16  is so narrow that the fuel flows into the bottom region  18  in a uniformly distributed fashion. Since the flow of fuel into the bottom region  18  is uniformly distributed, the fuel flows at a low speed, via the shortest route, directly to the closest region of the filter element  11  and a largely uniform fuel quantity flows through each region of the filter element  11 . 
     As is clear from  FIGS. 9 ,  10 , and  11 , the filter element  11  is essentially comprised of a folded filter material  40 . This folded filter material  40  is sheet-like and, depending on the medium to be filtered, has a thickness of approximately 0.3 mm to 1.5 mm, preferably 0.5 mm to 1.0 mm, in particular 0.7 to 0.8 mm. The filter material  40  is folded so that in the region of the bottom of the filter element  11  and in the region of the top of the filter element  11 , the filter material is folded over by almost 180°. This folding makes the filter element  11  as a whole relatively rigid and provides a large overall surface area for trapping impurities. As is clear from the drawings, the folds of the folded filter material  40  extend transversely to the longitudinal direction of the filter housing  2 , i.e. the folds extend parallel to the ends of the filter housing  2 . 
     The foregoing relates to preferred exemplary embodiments of the invention, it being understood that other variants and embodiments thereof are possible within the spirit and scope of the invention, the latter being defined by the appended claims.