Abstract:
A fuel injector for fuel-injection systems of internal combustion engines includes a solenoid coil, a tubular support acting as inner pole of the solenoid coil, and a filter element, the filter element being press-fitted with an outer contour of the tubular support of the fuel injector.

Description:
FIELD OF THE INVENTION 
     The present invention relates to a fuel injector and a method for installing a fuel injector. 
     BACKGROUND INFORMATION 
     In known fuel injectors, fuel filters are pressed into a fuel-intake nipple and affixed therein by a brass ring. This manner of fastening, first of all, involves the risk of abrasion and the formation of chips, which can lead to malfunctions of the fuel injector. On the other hand, the use of expensive brass as a component material is a cost factor that considerably increases the cost of the fuel injector. 
     A fuel injector, in which a fuel filter is manufactured in one piece with a retaining collar, is described in German patent document DE 43 25 842. The retaining collar radially extends beyond the fuel intake nipple and has a lip outside the fuel intake nipple. The circumferential lip of the retaining collar, together with a groove on the outer circumference of the fuel intake nipple, forms a snap-in connection by which the fuel filter is fastened in a defined manner. Only a clearance fit exists between the base element of the fuel filter and the inner wall of the fuel intake nipple, so that any build-up of shavings in the interior of the fuel injector is prevented. 
     A particular disadvantage of the fuel injector described in German patent document DE 43 25 842 is the large amount of processing time spent in affixing the filter to either the adjusting sleeve or the fuel intake nipple. In addition, the filter and adjusting sleeve are made of different materials, whereby shavings and abrasion are formed at the contact surfaces, predominantly on the plastic of the filter, which can lead to malfunctions of the fuel injector due to the deposition of the particles. 
     SUMMARY 
     In contrast to the known art, the fuel injector according to the present invention and the method according to the present invention for installing a fuel injector provide the advantage of a quick and cost-effective production and installation, as well as a reliable fixation of the filter element in the fuel injector, without the risk of shavings. 
     This is achieved by press-fitting the filter element with an outer contour of a tubular support of the fuel injector. 
     The outer contour of the tubular support advantageously has grooves into which a fiber glass plastic extrusion coat of the filter element is press-fitted under pressure. 
     It is also advantageous that the grooves are able to be introduced in the tubular support in a simple manner by machine-cutting or with the aid of a structural steel. 
     It is also advantageous that the press-fitting of the filter element is implemented by the installation of an extension sleeve whose inner diameter is slightly smaller than an outer diameter of the filter element. 
     The filter element is advantageously able to be manufactured like conventional filter elements, in the shape of a cup and made from cloth material and a fiber glass plastic extrusion coat. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1A  shows a schematic sectional view through an exemplary embodiment of a fuel injector according to the known art. 
         FIG. 1B  shows a schematic cut-away view of region IB of the fuel injector shown in  FIG. 1A . 
         FIG. 2A  shows a schematic representation of an exemplary embodiment of a filter element for a fuel injector configured according to the present invention. 
         FIG. 2B  shows a schematic cut-away view of a fuel injector configured according to the present invention, having a filter element according to  FIG. 2A . 
     
    
    
     DETAILED DESCRIPTION 
     For a better understanding of the measures according to the present invention,  FIG. 1A , first of all, shows a part-sectional, schematic representation of a longitudinal section through a fuel injector  1  according to the known art, which is suited, in particular, for the injection of fuel into an intake manifold (not shown further) of an internal combustion engine. 
     Fuel injector  1  includes a magnetic coil  2  which is wound on a coil brace  3 . Coil brace  3  is encapsulated in a valve housing  4  and sealed off by a lid  5 . A contact tag  6  is formed on coil brace  3 . 
     Coil brace  3  is penetrated by a valve sleeve  7 , which has a tubular design and includes a tubular support  8  wedged or soldered therein, which is used as inner pole of magnetic coil  2 . Valve housing  4 , for example, may be used as outer pole of magnetic coil  2 . Downstream from tubular support  8  is an armature  9  which is designed in one piece with a valve needle  10 . Flow-through orifices  11  are provided in valve needle  10 , which guide the fuel flowing through fuel injector  1  toward a sealing seat. 
     An annular filter  12  for filtering the fuel may be disposed in the region of flow-through orifices  11 . Valve needle  10  is in operative connection, e.g., by welding, with a valve-closure member  13  having a spherical shape in the exemplary embodiment, valve-closure member  13  forming a sealing seat together with a valve-seat body  14 . Downstream from the sealing seat, at least one spray-discharge orifice  15  is formed in a spray-orifice plate  34 , via which the fuel is injected into the intake manifold (not shown further). 
     In the rest state of fuel injector  1 , armature  9  is acted upon by a restoring spring  16  in such a way that fuel injector  1  is held closed by the contact pressure of valve-closure member  13  on valve-seat body  14 . Restoring spring  16  is situated in a recess  17  of armature  9  or tubular support  8  and is prestressed by an adjusting sleeve  18 . 
     On the inflow side of adjusting sleeve  18 , a cup-shaped filter element  19  is pressed into valve sleeve  7 . Filter element  19  is provided with a brass ring  20 , which allows reliable support of filter element  19  in fuel injector  1 . 
     The fuel supplied by a central fuel supply  22  flows through fuel injector  1 , through recess  17  and flow-through orifices  11 , to the sealing seat and to spray-discharge orifice  15 . 
     If an electric current is provided to magnetic coil  2  via an electrical line (not shown further) and contact tag  6 , a magnetic field is generated that, if sufficiently strong, pulls armature  9  into magnetic coil  2 , counter to the force of restoring spring  16  and counter to the flow direction of the fuel. This closes a working gap  23  formed between armature  9  and tubular support  8 . The movement of armature  9  also carries along, in the lift direction, valve needle  10 , which is formed in one piece with armature  9 , so that valve-closure member  13  lifts off from valve-seat body  14  and fuel is guided to spray-discharge orifice  15 . 
     Fuel injector  1  is closed as soon as the electric current energizing magnetic coil  2  is switched off and the magnetic field has decayed to such a degree that restoring spring  16  presses armature  9  away from tubular support  8 , thereby moving valve needle  10  in the flow-off direction, and causing valve-closure member  13  to set down on valve-seat body  14 . 
       FIG. 1B , in a part-sectional view, shows a cut-away view of region IB of fuel injector  1  illustrated in  FIG. 1A . Identical components are identified with matching reference numerals. A repetitious description of already discussed components are omitted. 
     As already mentioned earlier, filter element  19  has the form of a cup and is made up of a filter  21 , which may be made from a cloth material  24 , and a brass ring  20  for fixating filter element  19  in fuel injector  1 . During the production, brass ring  20  is inserted in a molding die and, together with actual filter  21 , is provided with a glass fiber plastic extrusion coat  25 . Brass ring  20  is configured as deep-drawn component. Brass ring  20  and the complex sealing of the molding die cause high production costs of filter element  19  with brass ring  20 . 
     In contrast, a fuel injector  1  configured according to the present invention is provided with a filter element  19  according to  FIGS. 2A and 2B , which filter element is fixated directly on inner pole  8  of fuel injector  1 , without the aid of a brass ring  20 . 
       FIG. 2A , in a schematic sectional view, shows an exemplary embodiment of a filter element  19 , which is suitable for use in a fuel injector  1  configured according to the present invention. Filter element  19  has the shape of a cup. It is made of a cloth material  24 , which is provided with a fiber glass plastic extrusion coat  25 . 
     However, according to the present invention, as illustrated in  FIG. 2B , filter element  19  is mounted on tubular support  8 , acting as inner pole, of fuel injector  1 . At an inflow-side end  26  of tubular support  8 , grooves  27  are provided in an outer contour  28  of tubular support  8 , which grooves are able to be produced in a simple manner by machine-cutting or with the aid of a structural steel. Filter element  19  is slipped onto these grooves  27  in the region of glass fiber plastic extrusion coat  25 . Filter element  19  rests against a shoulder  29  of tubular support  8 . Slipped-on filter element  19  has a slightly larger diameter than tubular support  8 . 
     If an extension sleeve  30  is subsequently installed on tubular support  8 , which is used for the connection to a fuel-distributor line (not shown further), the outer diameter of filter element  19  is calibrated to the inner diameter of extension sleeve  30 , which is slightly smaller than the outer diameter of filter element  19 . This presses filter element  19  into grooves  27  of tubular support  8  in the region of glass fiber plastic extrusion coat  25 . A secure holding of the filter element in fuel injector  1  is ensured in this manner even with high temperature fluctuations. As a result of the measures according to the present invention, fuel injector  1  is able to be manufactured in a simple and more cost-effective manner because brass ring  20  is not required, without higher costs of other components. 
     The present invention is not limited to the exemplary embodiment represented and is suitable for other designs of fuel injectors  1 , e.g., for fuel injectors  1  for direct injection or fuel injectors  1  connected to a common-rail system.