Abstract:
A fuel injector, in particular for the direct injection of fuel into a combustion chamber of an internal combustion engine, includes a valve needle at whose discharge-side end a valve-closure member is positioned, which cooperates with a valve-seat surface, formed at a valve-seat member, to form a sealing seat. A spray-discharge orifice calotte connected to the valve-seat member of the fuel injector, or integrally formed in one piece with it, has at least three spray-discharge orifices not all extended axes of the spray-discharge orifices intersecting.

Description:
BACKGROUND INFORMATION 
   From German Patent Application No. DE 198 27 219, a fuel injection system for an internal combustion engine is known, which includes an injector that has a disk for adjusting the fuel jet, this disk including first nozzle orifices disposed along a first circle, and including second nozzle orifices disposed along a second circle. The second circle has a larger diameter than the first circle. The circles are positioned coaxially with respect to a center axis of the adjustment disk. Each orifice axis of the second nozzle orifices forms an acute angle to a reference plane that is perpendicular to the center axis of the valve body. The angle is smaller than that formed by each orifice axis of the first nozzle orifices with the reference plane. Therefore, fuel atomizations, which are injected through the first nozzle orifices, can be directed away from the fuel atomizations being injected through the second nozzle orifices. As a result, the fuel atomizations injected through the first nozzle orifices do not interfere with the fuel atomizations injected through the second nozzle orifices, thereby allowing an appropriate atomization of the injected fuel. 
   Disadvantageous in this related art is that, on an inflow-side of the disk for adjusting the fuel jet, the spacing of the nozzle orifices is smaller than it is on an outer side of the disk for adjusting the fuel jet facing away from a combustion chamber. As a result, the formation of an overall injection jet, made up of the individual fuel jets, is only possible in certain (setpoint) inputs. The spacing of the nozzle orifices must not fall below certain values if the stability and strength of the disk for adjusting the fuel are to be ensured. 
   From German Patent Application No. DE 198 04 463, a fuel injector for mixture-compressing internal combustion engines having external ignition is known, which is provided with at least one row of injection orifices distributed over the circumference of the injection nozzle. Fuel is selectively injected via the injection orifices to realize a jet-controlled combustion method by a mixture cloud being formed, at least one jet being aimed in the direction of the spark plug or its immediate vicinity for the ignition. Additional jets are provided for forming an at least approximately continuous or cohesive mixture cloud. 
   In this related art, the injection orifices with their extended axes on the side of the fuel inflow, are directed to a common intersection of the axes. An optimal strength of the spray-discharge section, which is penetrated by the injection orifices, cannot be achieved. 
   SUMMARY OF THE INVENTION 
   The fuel injection system according to the present invention, has the advantage over the related art that the spray-discharge orifices are evenly distributed over the surface of the spray-discharge orifice calotte. Even on the side of the spray-discharge orifice calotte facing the valve needle, there are no spaces between the spray-discharge orifices that are too narrow. The strength of the spray-discharge orifice calotte is at its maximum. 
   The spray-discharge orifices are advantageously configured on the spray-discharge orifice calotte in a way that maximizes the average respective clearances of adjacent axes. 
   Bores placed in a flat disk have a maximum mutual clearance when they are evenly distributed over the disk and when the extended axes of adjacent bores are in parallel to one another. In fuel injectors, however, the spray-discharge orifices are disposed on an essentially hemispherical spray-discharge orifice calotte. Moreover, the spray-discharge orifices must be aligned in such a way that the desired jet pattern is generated. Therefore, the axes of the spray-discharge orifices are not in parallel to one another. The alignment is implemented in that all the axes of the spray-discharge orifices intersect at one point on the side of the valve needle to the spray-discharge orifice calotte, and the location of the spray-discharge orifice on the spray-discharge orifice calotte determines the direction of the axis. When the spray-discharge orifices are moved further apart, so that the axes of adjacent spray-discharge orifices have the largest possible clearance when viewed as geometrical lines in space, a maximum strength of the spray-discharge orifice calotte is able to be obtained. Since the orientation of a spray-discharge orifice is then, up to a certain extent, independent of the location of the spray-discharge orifice on the spray-discharge orifice calotte, the spray-discharge orifices may be distributed evenly on the spray-discharge orifice calotte in an advantageous manner. The faults in the formation of a total jet pattern, made up of individual fuel jets of the spray-discharge orifices, which are caused by the spray-discharge orifices being moved further apart, are negligible. 
   In one advantageous specific embodiment, the maximally two axes in each case intersect, and the intersecting points of the intersecting axes lie on a plane of symmetry that is perpendicular to the plane of the spray-discharge calotte. The spray-discharge orifices whose axes intersect are disposed in mirror symmetry with respect to the plane of symmetry and are oriented such that an ellipse results in a jet cross-section across all fuel jets of the spray-discharge orifices. 
   It is advantageously possible to generate a jet cross-section which, in the overall jet pattern, has an elliptical form across all fuel jets, without all spray-discharge orifices being configured on a narrowly restricted, essentially elliptical segment of the surface of the spray-discharge orifice calotte. The spray-discharge orifices may be evenly distributed across the spray-discharge orifice calotte. 
   In another advantageous specific embodiment, the spray-discharge orifices are arranged in an essentially circular manner about an axis of symmetry of the spray-discharge orifice calotte. The axes of the spray-discharge orifices are then tangential to a cylinder around the axis of symmetry, and the fuel jets essentially form a cone at a certain distance from the spray-discharge orifice calotte. 
   This advantageous specific embodiment as well, has the advantage over the related art of a substantially stronger spray-discharge orifice calotte. 

   
     BRIEF DESCRIPTION OF THE DRAWING 
       FIG. 1  shows a schematic section through a first exemplary embodiment of a fuel injector, designed according to the present invention. 
       FIG. 2   a  shows a spray-discharge orifice calotte in a plan view, according to the related art, for an overall jet pattern having an elliptical cross-section, in a plan view from the direction of the fuel injector. 
       FIG. 2   b  shows a cross-section through the spray-discharge orifice calotte of  FIG. 2   a.    
       FIG. 3   a  shows a first variant of a spray-discharge orifice calotte, designed according to the present invention, in a plan view, for an overall jet pattern having an elliptical cross-section. 
       FIG. 3   b  shows a cross-section through the spray-discharge orifice calotte of  FIG. 3   a.    
       FIG. 4  shows an additional variant of a spray-discharge orifice calotte, designed according to the present invention, for a conical overall jet pattern, in a plan view. 
   

   DETAILED DESCRIPTION 
   A first exemplary embodiment of a fuel injector  1  according to the present invention is designed in the form of a fuel injector  1  of a fuel injection system for mixture-compressing internal combustion engines having externally supplied ignition. Fuel injector  1  is particularly suited for the direct injection of fuel into a combustion chamber (not shown) of an internal combustion engine. 
   Fuel injector  1  is made up of a nozzle body  2  in which a valve needle  3  is positioned. Valve needle  3  is mechanically linked to a valve-closure member  4 , which interacts with a valve-seat surface  6  positioned on a valve-seat member  5 , to form a sealing seat. In the exemplary embodiment, fuel injector  1  is an inwardly opening fuel injector  1 , which has a plurality of spray-discharge orifices  7 . Seal  8  seals nozzle body  2  from an outer pole  9  of a magnetic coil  10 . Magnetic coil  10  is encapsulated in a coil housing  11  and wound on a coil brace  12 , which rests against an inner pole  13  of magnetic coil  10 . Inner pole  13  and outer pole  9  are separated from each other by a constriction  26  and are interconnected by a non-ferromagnetic connecting part  29 . Magnetic coil  10  is energized via a line  19  by an electric current, which may be supplied via an electrical plug contact  17 . A plastic coating  18 , which may be extruded onto inner pole  13 , encloses plug contact  17 . 
   Valve needle  3  is guided in a valve-needle guide  14 , which is disk-shaped. A paired adjustment disk  15  is used to adjust the (valve) lift. An armature  20  is on the other side of adjustment disk  15 . It is connected by force-locking to valve needle  3  via a first flange  21 ; and valve needle  3  is connected to first flange  21  by a welded seam  22 . Braced against first flange  21  is a restoring spring  23  which, in the present design of fuel injector  1 , is prestressed by a sleeve  24 . Fuel channels  30   a  through  30   b  run in valve-needle guide  14 , in armature  20  and valve-seat member  5 . The fuel is supplied via a central fuel feed  16  and filtered by a filter element  25 . Fuel injector  1  is sealed from a distributor line (not shown further) by a gasket  28 . 
   On the spray-discharge side of armature  20  is a ring-shaped damping element  32  made of an elastomeric material. It rests on a second flange  31 , which is connected by force-locking to valve needle  3  via a welded seam  33 . 
   In the rest state of fuel injector  1 , armature  20  is acted upon by restoring spring  23 , in a direction opposite to its lift direction, in such a manner that valve-closure member  4  is sealingly held against valve seat  6 . In response to excitation of magnetic coil  10 , it generates a magnetic field which moves armature  20  in the lift direction, counter to the spring force of restoring spring  23 , the lift being predefined by a working gap  27 , which occurs in the rest position between inner pole  12  and armature  20 . First flange  21 , which is welded to valve needle  3 , is also taken along by armature  20  in the lift direction. Valve-closure member  4 , which is connected to valve needle  3 , lifts off from valve seat surface  6 , so that the fuel is spray-discharged through spray-discharge openings  7 . 
   In response to interruption of the coil current, following sufficient decay of the magnetic field, armature  20  falls away from inner pole  13  due to the pressure of restoring spring  23 , whereupon first flange  21 , being connected to valve needle  3 , moves in a direction counter to the lift. Valve needle  3  is thereby moved in the same direction, causing valve-closure member  4  to set down on valve seat surface  6  and fuel injector  1  to be closed. 
     FIG. 2   a  shows a plan view of spray-discharge orifice calotte  34  according to the related art, for an overall jet pattern having an elliptical cross-section. The view corresponds to the view from fuel injector  1  into the inside of the curvature of spray-discharge orifice calotte  34 . Spray-discharge orifices  35  are disposed approximately on a plane enclosed by an ellipse, and axes  36 , defined by the orientation of spray-discharge orifices  35 , intersect at an intersection  37 . 
     FIG. 2   b  shows a cross-section through spray-discharge orifice calotte  34  in  FIG. 2   a , which includes spray-discharge orifices  35 , axes  36  and intersection  37 . 
   As can be seen very clearly, spray-discharge orifices  35  must be arrayed in relatively close proximity to one another, so as to generate, due to their orientation, an overall jet pattern that has an elliptical cross-section. Especially on the upper side, facing fuel injector  1 , of spray-discharge orifice calotte  34 , spray-discharge orifices  35  come very close to one another. However, for reasons of production engineering, a minimum clearance of one spray-discharge orifice diameter must be observed. 
   In a plan view from the direction of valve-closure member  4  of fuel injector  1  of  FIG. 1 ,  FIG. 3   a  shows a first exemplary embodiment of a spray-discharge orifice calotte  37 , designed according to the present invention, for an overall jet pattern that has an elliptical cross-section. Spray-discharge orifice calotte  37  is designed in one piece, together with valve-seat member  5  of  FIG. 1 . The view corresponds to the inside view of the curvature of spray-discharge orifice calotte  37 . Spray-discharge orifices  38  are approximately evenly distributed in spray-discharge orifice calotte  37 . Axes  39 , defined by the orientation of spray-discharge orifices  38 , intersect as a pair in each case in a plane of symmetry  40 , which is perpendicular to the plane of spray-discharge orifice calotte  37 , when viewed from the drawing plane. 
     FIG. 3   b  shows a cross-section through spray-discharge orifice calotte  37  in  FIG. 3   a , which includes spray-discharge orifices  38  and axes  39  in the plane of symmetry  40  of  FIG. 3   a.    
   The advantageous configuration (array) and orientation of spray-discharge orifices  38  makes it possible to increase the strength of spray-discharge orifice calotte  37 . Spray-discharge orifices  38  are evenly distributed and have a greater mutual clearance, particularly on the inside of spray-discharge orifice calotte  37 . In contrast, errors in the overall jet pattern resulting from a shift in spray-discharge orifices  38  are negligible when working with an overall injection jet in close proximity to spray-discharge orifice calotte  37 . 
   In a plan view corresponding to the view of  FIG. 3   a ,  FIG. 4  shows another variant of a spray-discharge orifice calotte  41  for a conical overall jet pattern. Spray-discharge orifice calotte  41  has spray-discharge orifices  42  configured in an approximately circular manner. Axes  43 , defined by the orientation of spray-discharge orifices  42 , are tangential to the middle of an imaginary cylinder. 
   In this way, the same previously described advantages are obtained for a conical overall jet pattern. In particular, one may specify an alignment of the jet cone&#39;s center axis, relative to a fuel-injector axis, of 0°–70° for the conical jet, as well as an opening angle of 30°–100°. In addition, spray-discharge orifices  42  must not necessarily be configured in a graduated circle, but may also be evenly distributed in the form of a raster. 
   The present invention is not limited to the described exemplary embodiments and y also be used, for example, to generate a hollow cone or a fan jet.