Abstract:
A fuel injector for fuel injection systems of internal combustion engines, in particular for direct injection of fuel into the combustion chamber of an engine, including an actuator, a valve needle which is mechanically linked to the actuator and is acted upon by a restoring spring in a closing direction, for actuation of a valve closing body, which together with a valve seat face forms a sealing seat, and including a sleeve which pre-stresses the restoring spring. An adjusting body is situated adjustably in the sleeve so that a fuel amount flowing through the fuel injector per unit of time is a function of the position of the adjusting body in the sleeve.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     The present application is a continuation of U.S. patent application Ser. No. 10/089,668 filed on Aug. 21, 2002 now U.S. Pat. No. 7,429,007, which was a national-phase application based on international application PCT/DE01/02705 filed on Jul. 18, 2001, each of which is expressly incorporated herein in its entirety by reference thereto. 
    
    
     FIELD OF THE INVENTION 
     The present invention is related to a fuel injector and a method of adjusting a fuel injector. 
     BACKGROUND INFORMATION 
     German Published Patent Application No. 40 23 828 discusses a fuel injector and a method of adjusting a fuel injector. To adjust the amount of fuel to be delivered during the opening and closing operation of the electromagnetically operable fuel injector, a magnetically conductive material, e.g., in the form of a powder which alters the magnetic properties of the internal pole is introduced into a blind hole, and thus the magnetic force is varied until the actual measured flow rate of the medium corresponds to the predetermined setpoint flow rate. 
     Similarly, German Published Patent Application No. 40 23 826 discusses the insertion of an equalizing bolt into a blind hole of an internal pole including a recess on its periphery, inserting it to the extent that the actual measured amount corresponds to the predetermined setpoint amount, and thus varying the magnetic force until this is achieved. 
     German Patent Published Application No. 195 16 513 also discusses a method of adjusting the dynamic flow rate of a fuel injector. In this case, an adjusting element situated close to the magnetic coil outside the flow path of the medium is adjusted. In doing so, the size of the magnetic flux in the magnetic circuit, and thus the magnetic force, changes, so it is possible to influence and adjust the flow rate. The adjustment may be performed with when the fuel injector is either wet or dry. 
     German Patent Published Application No. 42 11 723 discusses a fuel injector and a method of adjusting the dynamic flow rate of the medium of a fuel injector, in which an adjusting sleeve including a longitudinal slot is pressed into a longitudinal bore in a connection piece up to a predetermined depth, the dynamic actual flow rate of medium of the injector is measured and compared with a setpoint flow rate of medium, and the pressed-in adjusting sleeve which is under a tension acting radially is advanced until the actual measured flow rate of the medium matches the predetermined setpoint flow rate of the medium. 
     In German Published Patent Application No. 44 31 128, to adjust the dynamic flow rate of medium of a fuel injector, the valve housing undergoes deformation due to the action of a deformation tool on the outer perimeter of the valve housing. This changes the size of the residual air gap between the core and the armature, and thus the magnetic force, so that it is possible to influence and adjust the flow rate of medium. 
     One disadvantage of the group of methods which influence the magnetic flux in the magnetic circuit is the great expense with regard to manufacturing costs, because the required static flow tolerances must be guaranteed, although this is difficult to implement. In particular, measurements of magnetic fields are complicated to perform and usually require cost-intensive methods and a test field. 
     It is believed that a disadvantage of the group of mechanical adjustment methods is the high degree of inaccuracy to which these methods may be subject. Furthermore, the opening and closing times of a fuel injector may be shortened only at the expense of electric power, so that the electric load on the components is increased, and the controllers are under greater stress. 
     In particular, the method referred to in German Published Patent Application No. 44 31 128, where the residual air gap between the core and the armature is varied by deformation of the valve housing, permits only a very inaccurate correction of the flow rate because shear stresses in the nozzle body may have a negative effect on the direction and size of the deforming force. Therefore, a high manufacturing precision is necessary for all parts. 
     SUMMARY 
     The exemplary fuel injector according to the present invention and the exemplary method according to the present invention for adjusting a fuel injector, due to the introduction of an adjusting body into a sleeve which may be pressed into the valve body, may allow the flow rate to be monitored and adjusted in a mechanical manner. 
     The flow rate may be adjusted after the fuel injector has already been installed. The adjusting body may be accessible from the outside on its end facing the fuel feed and may be displaced as desired in the sleeve and pushed into the aperture plate by an adjustment bolt after measurement of the actual amount. 
     The configuration of the sleeve including a thread which cooperates with a thread provided on the adjusting body may allow the adjusting body to be securely set in position very well. In addition, the adjusting body may be unscrewed from the sleeve again to replace it. 
     The aperture plate, whose cross section may be increased or reduced by introducing the adjusting body, may also be used in mass-produced fuel injectors. The adjustment of the adjusting body in the sleeve and the manufacture of the adjusting body, the sleeve and the aperture plate may be accomplished in a simple manner in terms of the manufacturing technology. 
     The static and dynamic flow rates may be adjusted separately, so that the preset flow rates need not be altered by further adjustments. 
     Other adjustment features of the fuel injector may not be affected by the adjustment of the flow rate through the sleeve and the adjusting body. 
     Exemplary embodiments of the present invention are illustrated in the diagrams and are explained in greater detail in the following description. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  shows a schematic sectional view through an exemplary embodiment of a fuel injector according to the related art. 
         FIG. 2  shows a detail of a schematic section through a first exemplary embodiment of the fuel injector according to the present invention in area II in  FIG. 1 . 
         FIG. 3  shows a detail of a schematic section through a second exemplary embodiment of the fuel injector according to the present invention in area II in  FIG. 1 . 
         FIG. 4  shows a detail of a schematic section through a third exemplary embodiment of the fuel injector according to the present invention in area II in  FIG. 1 . 
         FIG. 5A-C  show details of schematic cross sections through the interior part of the third exemplary embodiment of the fuel injector according to the present invention along line V-V in  FIG. 4  in various exemplary embodiments. 
         FIG. 6A  shows a detail of a schematic section through a fourth exemplary embodiment of the fuel injector according to the present invention in area II in  FIG. 1 . 
         FIG. 6B  shows a detailed view of the interior part of the fourth exemplary embodiment of the fuel injector according to the present invention. 
     
    
    
     DETAILED DESCRIPTION 
     Before describing three exemplary embodiments of a fuel injector according to the present invention in greater detail on the basis of  FIGS. 2 through 5 , a known fuel injector of the same design as in the exemplary embodiments, except for the measures according to the present invention, will first be explained briefly with regard to its essential components on the basis of  FIG. 1 . 
     Fuel injector  1  may be configured in the form of a fuel injector for fuel injection systems of internal combustion engines having spark ignition of a fuel-air mixture. Fuel injector  1  may be suitable for direct injection of fuel into a combustion chamber of an engine. 
     Fuel injector  1  may include a nozzle body  2  in which a valve needle  3  may be guided. Valve needle  3  may be mechanically linked to a valve closing body  4  which cooperates with a valve seat face  6  situated on a valve seat body  5  to form a sealing seat. In this exemplary embodiment, fuel injector  1  may be an inwardly opening fuel injector  1  including an injection orifice  7 . Nozzle body  2  may be sealed by a seal  8  with respect to stationary pole  9  of a magnetic coil  10 . Magnetic coil  10  may be encapsulated in a coil housing  11  and may be wound on a field spool  12  which may be in contact with an internal pole  13  of magnetic coil  10 . Internal pole  13  and stationary pole  9  may be separated by a gap  26  and may be supported on a connecting component  29 . Magnetic coil  10  may be energized over a line  19  by electric current supplied via an electric plug contact  17 . Plug contact  17  may be surrounded by a plastic sheathing  18  which may be integrally molded on internal pole  13 . 
     Valve needle  3  may be guided in a valve needle guide  14  which may be designed in the shape of a disk. A matching adjustment disk  15  may be used to adjust the lift. On the other side of adjustment disk  15  there may be an armature  20  which may be in a friction-locked connection with valve needle  3  via a flange  21 , the valve needle being joined to flange  21  by a weld  22 . A restoring spring  23  may be supported on flange  21 ; in the present design of fuel injector  1 , the restoring spring may be pre-stressed by a sleeve  24 . Fuel channels  30   a  through  30   c , which carry the fuel that may be supplied through a central fuel feed  16  and filtered through a filter element  25  to injection orifice  7 , run in valve needle guide  14 , armature  20  and on valve seat body  5 . Fuel injector  1  may be sealed by a seal  28  with respect to a receiving bore (not shown), e.g., in a fuel rail. 
     In the resting state of fuel injector  1 , armature  20  may be acted upon by restoring spring  23  against its direction of lift so that valve closing body  4  may be held sealingly on valve seat  6 . When magnetic coil  10  is energized, it creates a magnetic field which moves armature  20  in the direction of lift against the elastic force of restoring spring  23 , the lift being predetermined by a working gap  27  between internal pole  12  and armature  20  in the resting position. Armature  20  also entrains flange  21 , which may be welded to valve needle  3 , in the direction of lift. Valve closing body  4 , which may be mechanically linked to valve needle  3 , may be lifted up from the valve seat face, and fuel may be injected through injection orifice  7 . 
     When the coil current may be turned off, armature  20  drops back from internal pole  13  due to the pressure of restoring spring  23  after the magnetic field has subsided sufficiently, so that flange  21 , which may be mechanically linked to valve needle  3 , moves against the direction of lift. Valve needle  3  may be thus moved in the same direction, so that valve closing body  4  may be set down on valve seat face  6 , and fuel injector  1  may be closed. 
     In an excerpt of a sectional diagram,  FIG. 2  shows the detail of fuel injector  1  which is labeled as II in  FIG. 1 . 
     The first exemplary embodiment of fuel injector  1  according to the present invention illustrated in  FIG. 2  shows the inlet-side part of fuel injector  1  without filter element  25 , which is present in central fuel feed  16  in  FIG. 1 . Whereas  FIG. 1  shows only sleeve  24 , which may be needed for adjusting the dynamic fuel flow which may be influenced by the opening and closing times, the exemplary embodiment illustrated in  FIG. 2  also has an adjusting body  40  which may be inserted into sleeve  24  and may be used for adjusting the static fuel flow, i.e., the flow of fuel in the opened static state. Adjusting body  40  has a cylindrical shape in the present exemplary embodiment and may be configured with a taper in the form of a truncated cone on injection end  41 . On its injection end  42 , sleeve  24  may be closed by an aperture plate  43 . Aperture plate  43  and sleeve  24  may be designed in one piece or they may be manufactured as two different parts. In the present exemplary embodiment, sleeve  24  and aperture plate  43  form one overall part. For the sake of facilitating installation, sleeve  24  may include a lateral slot  44  which extends as far as aperture plate  43 . 
     To regulate the static fuel flow, adjusting body  40  may be displaced in sleeve  24  in the injection direction using adjustment bolt  45 . Then conical injection end  41  of adjusting body  40  may be pushed into aperture plate  43 . The fuel flow through fuel injector  1  decreases depending on how far injection end  41  of adjusting body  40  projects into a borehole  46  in aperture plate  43 . 
     The dynamic fuel flow may be determined by the position of sleeve  24 . The further sleeve  24  may be pressed into a central recess  47  in fuel injector  1  by a suitable tool, the greater is the pre-stress acting on restoring spring  23  and the longer it lasts until fuel injector  1  is opened in the opening operation or the faster fuel injector  1  may be closed in the closing operation. This means that the dynamic fuel flow through fuel injector  1  decreases with an increase in the pre-stress on restoring spring  23  or with an increase in the depth of installation of sleeve  24 . 
     If sleeve  24  is introduced into central recess  47  in a certain desired position, the static fuel flow through fuel injector  1  when the latter is open may be adjusted via adjusting body  40 . To determine the proper flow rate and the correct position of adjusting body  40  in sleeve  24 , first the actual flow through fuel injector  1  may be measured. The actual measured value may then be compared with a predetermined setpoint value of the flow rate. Then adjusting body  40  may be displaced in sleeve  24  in the direction of injection by adjustment bolt  45  until the actual value matches the setpoint value. Since it is no longer possible to remove adjusting body  40  from sleeve  24 , to this end fuel injector  1  must have a static flow rate which is greater than the setpoint value before adjusting the static flow rate. 
     When the setpoint value for the flow rate through fuel injector  1  has been reached, adjustment bolt  45  may be removed and instead filter element  25  may be inserted into central recess  47  of fuel injector  1 , as illustrated in  FIG. 1 . 
     In a detail of a sectional diagram,  FIG. 3  shows the detail of a second exemplary embodiment of fuel injector  1  which is labeled as II in  FIG. 1 . 
     The second exemplary embodiment of fuel injector  1  according to the present invention differs from the first exemplary embodiment illustrated in  FIG. 2  in the design of adjusting body  40  which may be screwed into sleeve  24 . To do so, sleeve  24  may be provided with an internal thread  51  and adjusting body  40  may be provided with an external thread  50 . Adjusting body  40  is thus no longer pressed into sleeve  24 , but instead may be screwed into it by using a suitable adjusting tool  52 , e.g., a screwdriver. To this end, an inlet end  53  of adjusting body  40  may include a tool groove  54  in which a corresponding projection  55  on adjusting tool  52  engages. 
     In this exemplary embodiment of fuel injector  1  according to the present invention, it is not necessary for the actual flow rate of fuel injector  1  at the beginning of the adjustment to be higher than the setpoint flow rate, because adjusting body  40  may be screwed into any desired position in sleeve  24  via external thread  50  and internal thread  51 . 
       FIG. 4  shows a third exemplary embodiment of fuel injector  1  according to the present invention in the detail labeled as II in  FIG. 1 . 
     In the present exemplary embodiment, sleeve  24  does not include an aperture plate  43 , but instead may be configured as a hollow cylinder including a side slot  44 . Adjusting body  40  may be cylindrical and may include an axial groove  60  on its outer periphery. Groove  60  may have various cross sections and begins on injection end  41  of adjusting body  40 , continuing to inlet end  53  of adjusting body  40  as it becomes wider. 
     The flow rate through fuel injector  1  may be adjusted by a displacement of adjusting body  40  in the direction of injection. In contrast with the exemplary embodiments in  FIGS. 2 and 3 , where the fuel flow rate through fuel injector  1  decreases with an increase in the depth to which adjusting body  40  may be screwed or pressed into sleeve  24 , in the present exemplary embodiment the flow rate increases with an increase in the depth of insertion of adjusting body  40 . 
     When adjusting body  40  is inserted into sleeve  24  and has been pushed in to the extent that injection end  41  of adjusting body  40  and injection end  41  of sleeve  24  are flush with one another, there may be only minimal fuel flow through fuel injector  1  or none at all. The further adjusting body  40  may be pressed through sleeve  24  in the direction of injection, the greater is the wetted cross section made available for flow through groove  60 . 
     With this arrangement the flow rate need not be measured repeatedly and compared with the setpoint value, but instead adjusting body  40  may be pushed continuously further into sleeve  24  until the actual value of flow through fuel injector  1  matches the setpoint value. 
       FIGS. 5A-5C  show cross sections through injection end  41 ,  42  of adjusting body  40  and sleeve  24  along line V-V. In adjusting body  40 , which fills up sleeve  24 , groove  60  may be configured so that fuel flows through it in the direction of the valve seat. 
     Groove  60  may have various cross sections. In the first exemplary embodiment, which is illustrated in  FIG. 5A , groove  60  is U-shaped, while the exemplary embodiment illustrated in  FIG. 5B  includes a C-shaped groove  60 . 
     The exemplary embodiment illustrated in  FIG. 5C , which includes a flattened planar area  60  instead of groove  60 , may be simple to manufacture. Adjusting body  40  thus assumes the shape of a notched cylinder. 
       FIG. 6A  shows a fourth exemplary embodiment of fuel injector  1  according to the present invention. In contrast with preceding exemplary embodiments, sleeve  24  may include an external thread  57  which cooperates with an internal thread  58  of central recess  47  of fuel injector  1 . The position of sleeve  24  in central recess  47  of fuel injector  1  may thus be adjusted by turning it by using a suitable adjusting tool  56 . The inlet end of sleeve  24  may include a two-step recess  59 , the diameter of which tapers in two steps  61  and  62  in the direction of the fuel flow. 
     In the direction of injection, sleeve  24  may be supported on an intermediate sleeve  31  which may be clamped between sleeve  24  and restoring spring  23 . This results in no rotational force being applied to restoring spring  23  when screwing in sleeve  24 , thus preventing metal shavings from being removed and also preventing the resulting contamination of fuel injector  1 . 
     The dynamic fuel flow may be defined by the position of sleeve  24 , as already explained above. The further sleeve  24  may be screwed into central recess  47  of fuel injector  1  using adjusting tool  56 , which may be a hexagon socket wrench, for example, the greater may be the pre-stress acting upon restoring spring  23 , and the longer it takes for fuel injector  1  to be opened in the opening operation and the more rapidly fuel injector  1  may be closed in the closing operation. This means that the dynamic fuel flow through fuel injector  1  decreases with an increase in the pre-stress of restoring spring  23  and with an increase in the depth of installation of sleeve  24 . Tool  56  then engages in recess  59  in sleeve  24  at the first step  61 . The position of adjusting body  40  in sleeve  24  is not affected by screwing in sleeve  24  using adjusting tool  52 . 
     When sleeve  24  is brought into a certain desired position in central recess  47 , the static fuel flow which flows through fuel injector  1  when the latter is opened may be adjusted via adjusting body  40 . In the present exemplary embodiment this second adjustment step is identical to the method illustrated in  FIG. 4 . Only stepped recess  59  in sleeve  24  is different, because adjusting body  40  may be displaced by tool  45 , which has a smaller diameter than adjusting tool  56 . Adjusting tool  45  thus acts on second step  62 , without influencing the adjustment of sleeve  24  in recess  47  of fuel injector  1 . 
     Sleeve  24  including external thread  57  may be combined with any desired adjusting body  40 , in particular, with adjusting bodies  40  described in conjunction with  FIGS. 2 and 3 . Thus, for example, an exemplary embodiment may allow the positions of sleeve  24  as well as adjusting body  40  to be varied by turning them by using suitable adjusting tools  56  and  52 . 
     The present invention is not limited to the exemplary embodiments presented here and it may be suitable for any configuration of fuel injectors  1 , e.g., for fuel injectors  1  including piezoelectric or magnetostrictive actuators or outwardly opening fuel injectors  1 .