Patent Publication Number: US-2005116056-A1

Title: Fuel injector and method for installing a fuel injector in a valve seat

Description:
FIELD OF THE INVENTION  
      The present invention relates to a fuel injector, and a method for installing a fuel injector in a valve seat.  
     BACKGROUND INFORMATION  
      At the outer periphery of various fuel injectors, a plurality of sealing elements in the form of sealing rings may be arranged in succession so as to ensure an effective sealing of the fuel injector from a valve seat.  
      For instance, German Patent Application No. 28 27 789 refers to providing two sealing rings at a stepped inflow connector of the fuel injector. These may be embodied as whole ring stacks, which then include a stuffing-box ring, an o-ring, an asbestos ring cord, and a plastic fusion ring arranged in immediate succession. German Patent Application No. 28 27 878 refers to fuel injectors whose sealing is accomplished via sealing stacks, additional rings, having so-called emergency-sealing properties, being provided in addition to the actual sealing rings in o-form. Furthermore, German Patent Application No. 28 27 850 refers to spacing two sealing rings at the periphery of the fuel injector by using a shoulder that radially projects beyond the outer circumference of the inflow-connecting piece.  
      Furthermore, a sealing system on a fuel injector is referred to in German Patent Application No. 37 03 615, in which two sealing rings in each case surround one of two connecting pieces independently from one another and appropriately seal it from a fuel-supply line.  
      Moreover, German Patent Application No. 197 35 665 refers to a fuel-injection system in which a fuel injector is connected via an intermediate piece to a valve-seat connector of a fuel-supply line and sealed therefrom. In this arrangement, both the inflow connector of the fuel injector and also the intermediate pieces each have a sealing ring at the outer circumference, which spatially are thus clearly located at a distance from one another.  
     SUMMARY OF THE INVENTION  
      The exemplary fuel injector according to the present invention provides a sealing system having two sealing rings at its outer periphery, which may be especially easy to install, avoid excessive expansion and excessive spread of the sealing rings and may therefore basically avoid damage of the sealing rings. Nevertheless, it may guarantee sufficiently large support shoulders for the sealing rings and completely prevent the release of hydrocarbons into the environment, in compliance with ever stricter environmental demands.  
      Of particular advantage may be the simple handling of the two partial components of the intermediate ring. While the inner support ring may be installed in a very simple manner in a groove on the intake connector of the fuel injector by way of an inwardly projecting lip, the outer ring may be snapped into place on the support ring in an uncomplicated and reliable manner.  
      The locking bead on the support ring used for locking is arranged such that the high compression forces of the one sealing ring during the installation of the fuel injector in the receiving socket are absorbed by an upper horizontal locking surface. The lower axial demounting forces of the other sealing ring are sufficiently absorbed by a lower locking surface of the locking bead, which has a slanted configuration.  
      The exemplary method according to the present invention for installing a fuel injector in a valve seat may have the advantage that the overall installation may be performed in a fully automatic manner. In an especially advantageous manner, the sealing rings are handled very gently during the mounting, so that damage to the sealing rings is excluded. It may be especially advantageous that the sealing rings, despite being inserted in separate ring chambers, are barely spread open, so that there is no need to stretch them to a dangerous extent. Because the intermediate ring is arranged or configured in two parts, it is ensured that the first sealing ring is able to be installed without being overstretched, yet sufficiently large support shoulders are subsequently available for both sealing rings. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       FIG. 1  shows an inflow-side end of a fuel injector having a sealing system configured according to the present invention for sealing the fuel injector from a valve seat.  
       FIG. 2  shows an enlargement of the cut-out section II in  FIG. 1 . 
    
    
     DETAILED DESCRIPTION  
       FIG. 1  shows a partial representation of a fuel injector  1 , which, for instance, is embodied as a fuel injector for the direct injection of fuel into the combustion chamber of a mixture-compressing internal combustion engine having external ignition. By way of an inflow-side end  2 , fuel injector  1  projects into a corresponding valve seat  3 .  
      Valve seat  3  is embodied, for instance, as a cup-shaped intake connecting piece  4 , which constitutes part of a fuel-supply line (not shown further), such as a fuel rail. The fuel-supply line usually has a plurality of intake connecting pieces  4 , so that the fuel conveyed via the fuel-supply line may be distributed to a plurality of fuel injectors  1 . Intake connecting piece  4  has a stepped arrangement or configuration, for example, and, at its end facing away from the fuel-supply line, has one or a plurality of affixation elements  5  projecting in the manner of a lip. These affixation elements  5  engage in openings  6  of an securing clamp  7 , which is used to reliably secure fuel injector  1  in valve seat  3 . Securing clamp  7  is inserted, for instance, in a circumferential groove  8  at the outer periphery of a plastic extrusion coat  9  of fuel injector  1 .  
      Fuel injector  1  is largely surrounded by plastic extrusion coat  9 , for example. However, at inflow-side end  2  of fuel injector  1 , a metal intake connector  11  for the supply of fuel to the interior of fuel injector  1  projects beyond plastic extrusion coat  9 . Above plastic extrusion coat  9 , two sealing rings  13 ,  14 , configured as O-rings, are situated at the outer periphery of intake connector  11 . Due to an intermediate ring  15  configured according to the exemplary embodiment of the present invention, the two sealing rings  13 ,  14 , which follow each other closely in the axial direction, are positioned at a spatial distance from one another. Forming the upstream end of fuel injector  1  is an upper retaining ring  16 , which is made of plastic and mounted on intake connector  11 . In this manner, both sealing rings  13 ,  14  are embedded between retaining ring  16  and upper end face  17  of plastic extrusion coat  9 , intermediate ring  15  forming two ring chambers  18 ,  19  for sealing rings  13 ,  14 .  
      In contrast to the sealing rings having so-called emergency-sealing properties known in part from the related art, the two sealing rings  13 ,  14  are two “full-fledged” sealing rings made of known elastomer sealing material. The necessity of two sealing rings immediately following one another at the periphery of fuel injector  1  results from the composition of certain fuels. In long-term use of sealing rings it has become apparent that hydrocarbons permeate through the elastomers normally used for sealing rings and may even permeate them completely. In order to fully prevent the emission of hydrocarbons into the environment in accordance with ever stricter environmental regulations, it may be advantageous to situate an additional sealing ring immediately behind a first sealing ring. In this manner, the second sealing ring following a sealing ring permeated in the manner described above, offers a substantially improved sealing reliability.  
      Intermediate ring  15 , which partitions the sealing chamber into two ring chambers  18 ,  19 , is made up of two sub-components. An inner support ring  22  engages, for instance, in a circumferential groove  23  at the periphery of intake connector  11 . Ideally, support ring  22  is extruded (injected) on the metal valve body, together with plastic extrusion coat  9  and retaining ring  16 , in one plastic-extrusion procedure. On its inner side, support ring  22  has a slanted lip  24 , which projects toward the inside and is able to be inserted in groove  23  with form accuracy.  
      Provided at the outer diameter of support ring  22  is a locking bead  25 , which projects radially outward and at which an outer ring  26 , which also belongs to intermediate ring  15 , is able to be snapped into place.  
      The region of locking bead  25  is shown in  FIG. 2  in an enlarged view. Locking bead  25  at support ring  22  is arranged or configured such that the high compression forces of second sealing ring  13  during the installation of fuel injector  1  in intake connecting piece  4  are absorbed by an upper locking surface  28 , which mostly extends perpendicularly to a longitudinal valve axis  30 . The lower axial demounting forces of first sealing ring  14  are sufficiently absorbed by a lower locking surface  29  of locking bead  25 , locking surface  29  having a slanted arrangement or configuration. Outer ring  26  is made of flexible plastic. When outer ring  26  is mounted on inner support ring  22 , this plastic expands and then locks into place in the limit position above locking bead  25 . Intermediate ring  15 , made up of outer ring  26  and support ring  22 , is used as support shoulder for second sealing ring  13 .  
      The mounting of the sealing system on intake connector  11  of fuel injector  1  is briefly explained in the following. As already described above, plastic extrusion coat  9 , inner support ring  22  of intermediate ring  15 , and retaining ring  16  are, for instance, simultaneously extruded on the metal valve body in one extrusion procedure. Subsequently, first sealing ring  14  is spread open, mounted on intake connector  11 , moved across support ring  22  and stripped into ring chamber  19 . Then, outer ring  26  is clipped onto inner support ring  22  to complete intermediate ring  15 . Second sealing ring  13  is then spread open, mounted on intake connector  11  and stripped into ring chamber  18 . With the aid of the sealing system mounted in this manner on intake connector  11 , fuel injector  1  may be inserted in valve seat  3 .  
      The exemplary embodiment and/or method of the present invention is not limited to the described exemplary embodiment or method. Thus, intake connector  11 , for instance, may have a stepped arrangement or configuration in the region of sealing rings  13 ,  14  and/or sealing rings  13 ,  14  may have different cross sections or diameters.