Abstract:
In a Fuel Filter arrangement for an internal combustion engine comprising a prefilter and a main filter mounted to the engine by a filter holder, the filter holder has a recess receiving the prefilter, which forms a plug-in unit removably inserted in the recess and position-locked therein.

Description:
BACKGROUND OF THE INVENTION 
     The invention relates to a fuel filter arrangement for an internal combustion engine. 
     From German Patent Specification 25 05 091, a fuel filter arrangement is known which includes a curved filter mounting bracket for mounting the main filter to the engine. 
     From German Offenlegungsschrift 37 10 807, a fuel filter arrangement is known which has a prefilter and main filter arranged in a fuel feed pipe leading to an injection pump of an internal combustion engine. The prefilter is conventionally mounted between the fuel tank and the feed pump at a poorly accessible location within the engine compartment, e.g., beneath the induction manifold in the region of the body side frame and engine mount. 
     The object of the invention is to mount the preliminary filter in the engine compartment in such a way as to facilitate maintenance service. 
     SUMMARY OF THE INVENTION 
     In a fuel filter arrangement for an internal combustion engine comprising a prefilter and a main filter mounted to the engine by a filter holder, the filter holder has a recess receiving the prefilter, which forms a plug-in unit removably inserted in the recess and position-locked therein. 
     As a result of the special configuration of the filter holder, which is no longer used to merely mount the main filter to the engine but is at the same time a receiving element for the prefilter and thus forms a structural unit for the prefilter and the main filter, the prefilter can be serviced just as easily as the main filter, which is arranged at an easily accessible location in the upper region of the engine compartment. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 shows a fuel filter arrangement with filter holder; 
     FIG. 2 is a top view of a prefilter with flange; and 
     FIG. 3 is a top view of a connecting piece of the fuel feed pipe and a locking member mounted on the filter holder. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
     As shown in FIG. 1, a fuel filter arrangement for an internal combustion engine includes a main filter 2 and prefilter 3 which are combined to form a structural unit. 
     The main filter 2 comprises a filter head 4 and a filter box 5. The filter head 4 is integral with a filter holder 6, which extends from the filter head with a roughly rectangular angle downwardly for almost the entire length of the filter box 5 and forms an engine mounting bracket. 
     The filter holder 6 has a cylindrical recess 7 formed for receiving the prefilter 3, which is composed of a flanged annular element 8 from which a cylindrical, elongated strainer insert 9 extends into the recess 7. 
     The strainer insert 9 has at its free end spacer bars 10, which serve as guide structures and spacers to provide an annular interspace 11 between the strainer insert 9 and the inner wall 12 of the recess 7. 
     The shoulder 13 formed in the wall defining the cylindrical recess 7 forms a support for the annular element 8 of the prefilter 3, the annular element 8 projecting partly into the recess 7 and supporting a sealing ring 15 between its lowermost edge 14 and the inner wall 12 of the recess 7. The annular element 8 has an inner annular shoulder 16 serving as a stop structure for a connecting piece 17 of a fuel feed pipe 18 which is not shown in FIG. 1. The connecting piece is disposed on the fuel inlet side and is inserted into the annular element 8 so as to be sealed therein. An outer collar 19 which is part of the connecting piece 17 is supported on the annular shoulder 16 of the annular element 8. 
     At its upper end the annular element 8 has a sidewardly projecting structure 20 with an opening receiving a projection 22 which is provided on the filter holder 6 and is matched to the height of the flange 20. 
     The annular element 8 with flange 20, outer collar 19 of the connecting piece 17 and projection 22 form a plane on which a flat locking plate 23 is disposed, which is screwed to the filter holder 6 at the projection 22 and fixes both the prefilter 3 and the connecting piece 17 in place. 
     The connecting piece 17 extends essentially at a right angle with respect to the feed pipe 18, the cylindrical section 24 protruding out of the prefilter and being provided with a stop 25 engaged by the locking plate 23 which partially embraces the section 24 so as to serve also as a rotation lock for the connecting piece 17. The locking plate 23 also overlays the collar 19 to axially lock the connecting piece 17 in the annular element 8 and both in the cylindrical recess 7. 
     The fuel entering the filter flows via the connecting piece 17 into the prefilter 3 and flows through the strainer insert 9 from the inside thereof out into the annular space 11 and downwardly to a collecting chamber 26 from where it leaves the prefilter through a fuel outlet duct 27. 
     Due to the flow direction from the inside to the outside of the strainer insert 9 impurities remain within the strainer insert 9. It is thus guaranteed that during a strainer insert change no impurities will enter the fuel outlet duct 27 of the filter holder 6 which is connected to the feed pump.