Abstract:
A fuel injector, in particular for a high-pressure injector for direct injection of fuel into a combustion chamber of an internal combustion engine, has compression of a fuel/air mixture with spark ignition. On the downstream end of the valve a valve seat element is provided, to which a perforated disk acting as a flow restrictor is connected downstream. A swirl element is situated upstream from the valve seat which imparts an atomization-promoting rotational motion to the fuel to be injected. In the valve seat element downstream from the valve seat, an elongated outlet orifice is provided which opens directly into an orifice in the perforated disk attached to the valve seat element. The width of the outlet orifice is greater than the width of the orifice in the perforated disk, at least at its narrowest location, so that it is possible to adjust the steady-state flow rate of the valve at the orifice.

Description:
FIELD OF THE INVENTION 
   The present invention relates to a fuel injectors used in internal combustion engines. 
   BACKGROUND INFORMATION 
   An electromagnetically actuatable fuel injector is described in German Patent No. 39 43 005 in which multiple disk-shaped elements are situated in the seat area. When the magnetic circuit is energized, a flat valve plate acting as a flat armature is lifted up from a valve seat plate situated at the opposite end which cooperates with the flat valve plate and together with the flat valve plate forms a plate valve part. A swirl element is situated upstream from the valve seat plate which imparts a circular rotational motion to the fuel flowing to the valve seat. A stop plate delimits the axial path of the valve plate at the opposite end from the valve seat plate. The valve plate is enclosed by the swirl element with a large amount of leeway and thus the swirl element guides the valve plate. Multiple tangentially running grooves are provided in the swirl element on its lower front face which extend from the outer periphery into a center swirl chamber. When the swirl element rests with its lower front face on the valve seat plate, the grooves act as swirl channels. The spray-discharge orifice provided in the valve seat plate determines the spray-discharge geometry via its length and diameter, and therefore must be introduced with great precision. 
   In addition, a fuel injector is described in European Patent Application No. 350 885 in which a valve seat body is provided, and a valve closing body which is situated on an axially movable valve needle cooperates with a valve seat face of the valve seat body. In a recess in the valve seat body upstream from the valve seat face a swirl element is situated which imparts a circular rotational motion to the fuel flowing to the valve seat. A stop plate delimits the axial path of the valve needle and has a central orifice which provides a certain guiding of the valve needle. Multiple tangentially running grooves are provided in the swirl element on its lower front face which extend from the outer periphery into a center swirl chamber. When the swirl element rests with its lower front face on the valve seat body, the grooves act as swirl channels. In this fuel injector as well, the size of the spray-discharge orifice provided in the valve seat body determines the spray-discharge geometry, so that this spray-discharge orifice must also be shaped very precisely. 
   The multilayer metal plating technique for manufacturing perforated disks which are particularly suited for use in fuel injectors has been described in detail in German Patent Application No. 196 07 288. This principle for manufacturing disks by single or multiple metal electrodeposition of various layered structures to produce a one-piece disk is expressly incorporated by reference herein. 
   SUMMARY 
   The fuel injector according to the present invention has the advantage that it is particularly simple and inexpensive to manufacture. The perforated disk provided on the valve seat element may be easily and securely mounted. Perforated disks having simple and yet very different orifice structures may be manufactured on a large scale very easily and in a precisely reproducible manner. The perforated disks are components which are easily handled in manufacturing and fine machining operations. Since in the perforated disks according to the present invention the flow-determining orifice cross section is provided with a flow restriction function, it is has the advantage that no high demands are placed on the dimensional accuracy of the outlet opening in the valve seat element downstream from the valve seat face. The valve seat element is therefore considerably easier to handle during manufacturing and machining. 
   The steady-state flow rate of the valve may be adjusted using the perforated disk which acts as a flow restrictor and which may be easily manufactured, handled, and installed. 
   It is particularly advantageous to design the perforated disk with an orifice which is stepped or otherwise modified in its cross section. The narrowest section of the orifice then determines the steady-state flow rate, while it is possible for the remaining length of the orifice to influence the spray angle of the spray-discharged fuel. 
   If the perforated disk is manufactured by metal electrodeposition, for example, any desired orifice cross section may be provided very easily, thus making it possible for the shape of the jet to have an extremely variable design. 
   In the absence of high demands on the dimensional accuracy of the outlet in the valve seat element, the steady-state flow rate, the spray angle, and the shape of the jet may be adjusted very easily by the precise orifice contour of the perforated disk. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  shows a first embodiment of a fuel injector according to the present invention. 
       FIG. 2  shows a downstream valve end of a second embodiment of a fuel injector according to the present invention. 
       FIG. 3  shows a downstream valve end of a third embodiment of a fuel injector according to the present invention. 
   

   DETAILED DESCRIPTION 
   The valve, which is illustrated as an exemplary embodiment in  FIG. 1  as an electromagnetically actuatable injector for fuel injection systems in spark ignition internal combustion engines, has a tubular, substantially hollow cylindrical core  2  which is at least partially enclosed by a solenoid  1  and which acts as an internal pole of a magnetic circuit. The fuel injector is particularly suitable as a high-pressure injector for direct spray discharge of fuel into a combustion chamber of an internal combustion engine. A bobbin  3  made of plastic, which has a stepped design, for example, accommodates a winding of solenoid  1  and, in conjunction with core  2  and an annular, nonmagnetic intermediate part  4  having an L-shaped cross section which is partially enclosed by solenoid  1 , allows a particularly compact and short design of the injector in the region of solenoid  1 . 
   A pass-through longitudinal orifice  7  is provided in core  2  which extends along a longitudinal valve axis  8 . Core  2  of the magnetic circuit also serves as a fuel inlet connector, and longitudinal orifice  7  acts as a fuel supply duct. Above solenoid  1 , core  2  is firmly attached to outer metallic (ferritic, for example) housing part  14 , which, as a stationary pole or external guide element, closes the magnetic circuit and completely encloses solenoid  1 , at least in the circumferential direction. A fuel filter  15  is provided on the inflow side in longitudinal orifice  7  of core  2  for filtering out fuel components which because of their size could cause blockage or damage in the injector. Fuel filter  15  is attached by pressing it into core  2 , for example. 
   Core  2  together with housing part  14  forms the inflow-side end of the fuel injector. The upper housing part  14  extends just over solenoid  1 . A lower tubular housing part  18  is tightly and permanently joined to upper housing part  14  and encloses or accommodates for example an axially movable valve part having an armature  19 , a rod-shaped valve needle  20 , and an elongated valve seat support  21 . Both housing parts  14  and  18  are permanently joined together by a circumferential weld, for example. 
   In the embodiment illustrated in  FIG. 1 , lower housing part  18  and substantially tubular valve seat support  21  are permanently connected to one another by screwing, although welding, soldering, or bordering are also possible joining methods. A seal between housing part  18  and valve seat support  21  is created by a sealing ring  22 , for example. Valve seat support  21  has an internal through orifice  24  through its entire axial extension which runs concentrically with respect to longitudinal valve axis  8 . 
   At its lower end  25 , valve seat support  21  encloses a disk-shaped valve seat element  26  which is fitted into through orifice  24  and which has valve seat face  27  tapering in the downstream direction in the shape of a truncated cone, for example. Valve needle  20 , which may be rod-shaped and has a substantially circular cross section, is situated in through orifice  24  and has a valve closing section  28  on its downstream end. This valve closing section  28 , which for example has a spherical, partially spherical, or rounded shape, or which is conically tapered, cooperates with valve seat face  27  provided in valve seat element  26 . Downstream from valve seat face  27  at least one outlet orifice  32  for the fuel is provided in valve seat element  26 . 
   The injector may be actuated by electromagnetic means, for example. However, a piezoelectric actuator may also be used as an energizable actuator. In addition, actuation via a piston under controlled pressure load is possible. The electromagnetic circuit, which has solenoid  1 , core  2 , housing parts  14 , and  18 , and armature  19 , is used to axially move valve needle  20  and thus to open the injector against the elastic force of a restoring spring  33  situated in longitudinal orifice  7  of core  2 , and also for closing the injector. Armature  19  is connected to the end of valve needle  20  facing away from valve closing section  28  by a weld and is aligned with core  2 . In order to guide valve needle  20  during its axial movement together with armature  19  along longitudinal valve axis  8 , a guide orifice  34  is provided in valve seat support  21  on the end facing toward armature  19 , and a disk-shaped guide element  35  having a dimensionally accurate guide orifice  55  is provided upstream from valve seat element  26 . When moving in the axial direction, armature  19  is enclosed by intermediate part  4 . 
   A swirl element  47  is situated between guide element  35  and valve seat element  26 , so that all three elements  35 ,  47 , and  26  are situated one directly on top of the other and are accommodated in valve seat support  21 . The three disk-shaped elements  35 ,  47 , and  26  are tightly connected to one another with a material fit (weld spots or welds  60  in FIGS.  2  and  3 ). 
   The lift of valve needle  20  is delimited by the installation position of valve seat element  26 . When solenoid  1  is not energized, one end position of valve needle  20  is delimited by the contact of valve closing section  28  with valve seat face  27 , and when solenoid  1  is energized, the other end position of valve needle  20  is delimited by the contact of armature  19  with the downstream end face of core  2 . The surfaces of the components in the latter stop region are chrome-plated, for example. 
   Solenoid  1  is electrically contacted and thus energized via contact elements  43  which are provided with a plastic extrusion coating  44  on the outside of bobbin  3 . Plastic extrusion coating  44  may also extend over additional components (housing parts  14  and  18 , for example) of the fuel injector. An electrical connecting cable  45  running out of plastic extrusion coating  44  supplies power to solenoid  1 . 
     FIG. 2  shows a second embodiment of a fuel injector, of which only the downstream valve end is illustrated. Guide element  35  has a dimensionally accurate inner guide orifice  55  through which valve needle  20  moves during its axial motion. From the outer periphery inward, guide element  35  has multiple recesses  56  which are distributed over the periphery, thereby ensuring fuel flow along the outer periphery of guide element  35  into swirl element  47  and continuing in the direction of valve seat face  27 . 
   In the example embodiment shown in  FIG. 2 , valve seat element  26  has a circumferential flange  64  which engages from below with downstream end  25  of valve seat support  21 . Upper side  65  of circumferential flange  64  is ground while clamped together with guide orifice  55  and valve seat face  27 . The three-disk valve body including elements  35 ,  47 , and  26  is inserted until upper side  65  of flange  64  contacts end  25  of valve seat support  21 . The valve body is attached for example by a weld  61  produced by a laser in the contact region of both components  21  and  26 . Outlet orifice  32  is provided at an inclined angle, for example, with respect to longitudinal valve axis  8  and ends downstream in a protruding spray discharge region  66 . 
   A thin perforated disk  70  having a specific orifice structure is provided in spray discharge region  66  of valve seat element  26 . This perforated disk  70 , which for example is countersunk into an indentation  71  in spray discharge region  66  in valve seat element  26  on its downstream front face and meets flush with this front face, functions primarily as a flow restrictor. The steady-state flow rate is adjusted via the size of orifice  73 . Inner orifice  73  in perforated disk  70  has a smaller orifice diameter than does outlet orifice  32  in valve seat element  26 . Perforated disk  70  is attached to valve seat element  26  by a weld  72  (as shown), or attachment using a retaining ring may also be utilized. Perforated disk  70  is installed, for example, with the normal to its surface at a non-90-degree angle with respect to longitudinal valve axis  8 , so that the angle of inclination of outlet orifice  32  with respect to longitudinal valve axis  8  corresponds to orifice  73  in tilted perforated disk  70 . In this manner the longitudinal axes of outlet orifice  32  and orifice  73  coincide, and outlet orifice  32  and orifice  73  are put into alignment. The length of tubular outlet orifice  32  provided in valve seat element  26  is greater than the entire length of orifice  73  in perforated disk  70 , the lengths having a ratio for example of between 3 and 10 to 1; in the illustrated embodiment, they have a ratio of approximately 5 to 1. 
   In the example embodiment shown in  FIG. 2 , orifice  73  has a continuously cylindrical shape, whereas in the embodiment according to  FIG. 3  a stepped orifice  73  is provided. Orifice  73  in perforated disk  70  according to  FIG. 3  has a narrower upstream section  75  and a wider downstream section  76 . At least the narrower section  75  has a smaller orifice diameter than outlet orifice  32  of valve seat element  26 . While narrower section  75  of orifice  73  determines the steady-state flow rate, slightly enlarged section  76  may influence the spray angle of the spray-discharged fuel as well. 
   Perforated disks  70  having simple and yet widely differing orifice structures may be manufactured on a large scale very easily and in a precisely reproducible manner. Since, in the perforated disks  70  according to the present invention, the flow-determining orifice cross section is provided with a flow restrictor function, it is advantageous that no high demands are placed on the dimensional accuracy of outlet orifice  32  in valve seat element  26  downstream from valve seat face  27 . Valve seat element  26  is therefore considerably easier to handle during manufacturing and processing. 
   Perforated disks  70  can be manufactured by metal electrodeposition, in particular by multilayer metal plating. While the perforated disk  70  according to  FIG. 2  is formed from a single metal layer, the embodiment according to  FIG. 3  shows a perforated disk  70  having two layers, each layer being characterized by a respective constant internal orifice contour  75 ,  76  which is altered in the next layer. A double-layer perforated disk  70  may be produced, for example, by electrodeposition of two layers one on top of the other, both layers then being adhesively bonded to one another and ultimately forming a component. Using this technology, it is possible to create shapes of orifices  73  in perforated disks  70  which depart from a circular contour, such as triangular to n-sided or cloverleaf shapes or the like. Highly differing jet shapes may thus be easily created using a perforated disk  70  having such a design. 
   Using deep lithographic electroplating methods, the following features in the contouring may be realized:
         Layers having constant thickness over the disk surface,   As a result of the deep lithographic structuring, substantially vertical indentations in the layers which form the respective cavities having flow-through (due to the manufacturing process, deviations of approximately 3° in relation to optimally vertical walls may be present),   Desired undercuts and overlaps of the indentations due to the multilayer construction of individually structured metal layers,   Indentations having any cross-sectional shapes which are essentially parallel to the axis, and   One-piece design of the perforated disk, since the individual metal depositions directly follow one another in succession.       

   It is also possible to manufacture perforated disks  70  using stamping, embossing, erosion, or etching techniques. Thus, the orifice contour may also be provided in a very precise manner using laser beam drilling, erosion, or stamping techniques.