Abstract:
A fuel delivery unit of a motor vehicle comprises a prefilter arranged inside a swirl pot, said prefilter having a filter element, and at least one connection piece for connecting a supplementary filter element. The at least one connection piece, in its initial condition, is closed, and is opened when the supplementary filter element is attached. The invention allows the fuel delivery unit to be adapted to projected filter surfaces of the prefilter.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This is a U.S. national stage of application No. PCT/EP2007/056993, filed on 9 Jul. 2007, priority is claimed on Application No. 10 2006 032 100.6, filed 11 Jul. 2006, the contents both of which are incorporated here by reference. 
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The invention relates to a fuel delivery unit of a motor vehicle, with a swirl pot and with a prefilter which has a filter element and is intended for filtering the fuel flowing into the swirl pot. 
     2. Description of the Prior Art 
     Delivery units with swirl pots of this type are frequently used in motor vehicles nowadays and are known from practice. In the case of the known delivery units, the swirl pot is connected to the filter element of the prefilter. If an appropriately sized filter capacity of the prefilter is to be ensured, an appropriately sized filter element of the prefilter is used. A disadvantage of the known fuel delivery unit is that it is highly cost-intensive to keep different filter elements in stock. 
     SUMMARY OF THE INVENTION 
     The invention is based on the problem of developing a fuel delivery unit of the type mentioned at the beginning in such a manner that it can be adapted particularly cost-effectively to designated filter capacities. 
     This problem is solved according to one embodiment of the invention in that the prefilter has a support with at least one connection piece, which is closed in the basic state, for the installation of an additional filter element. 
     By means of this configuration, the fuel delivery unit according to one embodiment of the invention can be equipped with the additional filter element as well as with the filter element. The filter element preferably has a sufficient filter surface for most applications. If a particularly large filter capacity of the prefilter is to be ensured, the additional filter element can be fitted on the connection piece. Therefore, the fuel delivery unit according to the invention can be adapted particularly cost-effectively to the designated filter capacity. 
     The fuel delivery unit according to one embodiment of the invention is particularly compact if the support and a base plate closing the swirl pot delimit a collecting chamber for collecting the prefiltered fuel, if an intake connection of a fuel pump is connected to the collecting chamber, and if the connection piece protrudes into the interior of the swirl pot. 
     The support in one embodiment a closed wall with a plurality of connection pieces. In this case, the filter element is designed as the additional filter element and could be fitted on one of the connection pieces. The fuel delivery unit according to this embodiment of the invention is particularly compact if the filter element is designed as a partial region of the support. By means of this configuration, the swirl pot has at least the filter element which is designed as a partial region of the support. If the filter surface is to be enlarged, one or more other additional filter elements is or are fitted to the corresponding connection piece or connection pieces. 
     According to another embodiment of the invention, the prefilter has a particularly large filter surface if the filter element is adjacent to the at least one connection piece. 
     According to another embodiment of the invention, the installation of the prefilter turns out to be particularly simple if the filter element is connected to the swirl pot and/or to the support with a cohesive material joint. By means of this configuration, the swirl pot, in the basic state, has at least a single filter element and, if the need arises, can be provided with a particularly large surface area by the installation of the additional filter element on the connection piece. 
     The additional filter element to be fitted to the connection piece turns out to be particularly compact, according to another embodiment of the invention, on the additional filter element provided for installation on the connection piece has a connector and a filter fabric protruding from the connector, and if the filter fabric is of bag-shaped design. The bag-shaped filter fabric can be produced, for example, from a tubular filter fabric by the connector being connected to one end of the tubular filter fabric and the other end being closed. 
     According to another embodiment of the invention, the prefilter which is fitted on the support has a high degree of stability if the connection piece surrounds the connector of the attached additional filter element. Furthermore, the connector of the additional filter element is capable of sealing the opened connection piece. 
     The installation of the additional filter element is simplified, according to another embodiment of the invention, if the connection piece protrudes in the shape of a tube from the support, and if the support has an at least partially encircling groove as a predetermined breaking point within the connection piece. By means of this configuration, the additional filter element is pressed, upon installation, into the connection piece until the connector can break open the support at the encircling groove. Subsequently, the connector of the additional filter element is inserted in the connection piece and seals the latter. The connector preferably has an end edge for breaking open the predetermined breaking point. The additional filter element can therefore be fitted without a tool. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The invention permits numerous embodiments. To further clarify its basic principle, one of said embodiments is illustrated in the drawing and is described below. In the drawing 
         FIG. 1  is a partial section through a fuel delivery unit according to the invention; 
         FIG. 2  is schematically a longitudinal section through a swirl pot with a prefilter of the fuel delivery unit according to the invention from  FIG. 1 ; 
         FIG. 3  is a greatly enlarged illustration of a partial region of the prefilter from  FIG. 2  in the region of an additional filter; and 
         FIG. 4  is a greatly enlarged illustration of a partial region of the prefilter from  FIG. 2  in the region of a closed connection piece. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       FIG. 1  shows a delivery unit which is to be arranged in a fuel tank (not illustrated) of a motor vehicle and is intended for delivering fuel to an internal combustion engine (likewise not illustrated) of the motor vehicle. The delivery unit has a fuel pump  2  which is arranged in a swirl pot  1  and is driven by an electric motor, and a fine filter  3 . The fine filter  3  is likewise arranged in the swirl pot  1  and is connected to the fuel pump  2  via a fuel line  4 . Furthermore, the fine filter  3  has a feed connection  5  for a feed line leading to the internal combustion engine of the fuel tank. A line  7  for a suction jet pump (not illustrated) is connected to a connection  6  of the fuel pump  2 . The suction jet pump sucks up fuel from the surroundings of the swirl pot  1  and delivers said fuel into the swirl pot  1 . The swirl pot  1  serves to collect the fuel and has a base plate  8  and a casing  9  connected to the base plate  8  in a sealing manner. An intake connection  10  of the fuel pump  2  protrudes through a prefilter  11  into a collecting chamber  12  arranged between the base plate  8  and the prefilter  11 . The prefilter  11  has a planar filter element  19  which is connected to the casing  9  of the swirl pot  1  with a cohesive material joint and in a sealing manner 
     and has two connection pieces  13 ,  14 . An additional filter element  15  is connected to one of the connection pieces  13  while the other connection piece  14  is sealed. 
     Fuel flowing into the swirl pot  1  passes via the prefilter  11  into the collecting chamber  12  and therefore to the intake connection  10  of the fuel pump  2 . The fuel pump  2  is therefore capable of sucking up prefiltered fuel from the swirl pot  1  and of delivering said fuel via the fine filter  3  to the feed connection  5  for the feed line. The casing  9  of the swirl pot  1  has an edge  17  which engages over a supporting edge  16  of the base plate  8 . The edge  17  and the supporting edge  16  are connected to each other in a sealing manner. 
       FIG. 2  shows schematically a sectional illustration through the swirl pot  1  with the prefilter  11  from  FIG. 1 . To simplify the drawing, other components, such as the fuel pump  2  and the fine filter  3 , are not illustrated in  FIG. 2 . The prefilter  11  has a support  18  for holding the connection pieces  13 ,  14  and holds the planar filter element  19  and the additional filter element  15 . Furthermore, the support  18  with the filter element  19  and the additional filter element  15  together with the base plate  8  delimit the collecting chamber  12 . 
       FIG. 3  shows, on a greatly enlarged scale, the additional filter element  15  attached in one of the connection pieces  13  of the prefilter  11 . The additional filter element  15  has a bag-shaped filter fabric  20  with a connector  21  which is plugged into one of the connection pieces  13  of the support  18 . The connection piece  13  of the support  18  therefore surrounds the connector  21  of the additional filter element  15 . A filter fabric  22  of the filter element  19  arranged on the support  18  is adjacent to the connection piece  13 . 
       FIG. 4  shows the sealed connection piece  14  with adjacent regions of the prefilter  11 . 
     In order to enlarge the filter surface of the prefilter  11 , an additional filter element  15  like the one illustrated in  FIG. 3  can likewise be attached to said connection piece  14 . The connection piece  14  has an encircling groove  23  as a predetermined breaking point. When the additional filter element  15  is attached, the encircling groove  23  is broken open. The additional filter element  15  is therefore held on the connection piece  13  in a sealed manner, as illustrated in  FIG. 3 . 
     In the basic state after the manufacturing of the prefilter  11 , the connection pieces  13 ,  14 , as per the one from  FIG. 4 , are sealed. The prefilter  11  therefore exclusively has the filter surface formed by the filter fabric  22  of the planar filter element  19 . If the prefilter  11  is to be provided with an enlarged filter surface, the additional filter element  15  is attached to one or to both connection pieces  13 ,  14 . The filter surface can therefore be adapted with a large number of identical parts in a manner corresponding to the number of connection pieces  13 ,  14  provided on the support  18 . 
     Thus, while there have shown and described and pointed out fundamental novel features of the invention as applied to a preferred embodiment thereof, it will be understood that various omissions and substitutions and changes in the form and details of the devices illustrated, and in their operation, may be made by those skilled in the art without departing from the spirit of the invention. For example, it is expressly intended that all combinations of those elements and/or method steps which perform substantially the same function in substantially the same way to achieve the same results are within the scope of the invention. Moreover, it should be recognized that structures and/or elements and/or method steps shown and/or described in connection with any disclosed form or embodiment of the invention may be incorporated in any other disclosed or described or suggested form or embodiment as a general matter of design choice. It is the intention, therefore, to be limited only as indicated by the scope of the claims appended hereto.