Electromagnetically actuated fuel injection valve
BACKGROUND OF THE INVENTION 
     The invention relates to an electromagnetically actuated fuel injection valve for timed, low pressure fuel injection systems of internal combustion engines employing injection into the induction manifold of the engine. The fuel injection valve includes a soft iron core, disposed within the valve housing, the latter being provided with a fixed magnetic winding and further includes a coaxial armature whose face is separated from the face of the soft iron core by an air gap. The fuel injection valve also includes a valve needle which is adapted to reciprocate within the housing and, more particularly, within the nozzle body of the valve, with one end thereof being fixedly held within a corresponding coaxial bore of the armature. 
     Known injection valves of the type described above are manufactured in large quantities, and, in this type of valve, the needle is threaded into the armature and secured against relative rotation by means of an adhesive material. However, this material has been known to be carried into the valve needle guide bushing, thus causing the needle to be seized therein. 
     OBJECT AND SUMMARY OF THE INVENTION 
     It is an object of the invention to provide an improved fuel injection valve of the known type. More specifically, it is an object of the invention to provide a connection between the valve needle and the armature which lacks the above mentioned disadvantages of the known connections and which is also suitable for mass production. 
     It is another object of the invention to provide a method for producing the improved fuel injection valve. 
     Thus, according to the invention, the foregoing objects are attained by providing the upper extremity of the valve body with a series of annular ribs that are spaced from one another by undercut areas or grooves, said valve body being subsequently assembled by a press-fit within a bore in a magnetic armature of the valve. 
     An advantageous method of producing the connection between the needle and the armature provides that the valve needle is temporarily placed in a holding fixture and that an armature with a central bore is placed over the top of the valve needle. The diameter of the outer cylindrical surface of the armature is slightly larger in the region adjacent to the top of the valve needle than elsewhere. Subsequently, a swaging ring is placed over the armature and is drawn in the direction of the longitudinal axis of the assembly. This operation reduces the outside diameter of the armature to equal the inside diameter of the ring, thereby also decreasing the interior bore diameter and forcing the displaced armature material partially into the annular undercut areas or grooves of the valve needle. 
     Another advantageous embodiment of the injection valve according to the invention provides the valve needle with one or more flattened areas in its outer surface capable of permitting fuel flow longitudinally thereof through the channel formed between the needle and the armature in the press-fit region. 
    
    
     The invention will be better understood as well as further objects and advantages become more apparent from the ensuing detailed specification and exemplary embodiment taken in conjunction with the drawing. 
     BRIEF DESCRIPTION OF THE DRAWING 
     The drawing represents an exemplary embodiment of the invention as applied to an injection valve using longitudinal stroke metering. 
     FIG. 1 is an axial section of the injection valve according to the invention; and 
     FIG. 2 depicts the valve needle and the armature in a supporting jig just prior to the swaging operation. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     The injection valve shown in FIG. 1 has a steel housing containing a central bore 2 for receiving the magnetic winding assembly including the winding. The bore 2 is continued in a substantially narrower, coaxial bore 5. Coaxial with and located within the magnetic winding assembly 3 is a soft iron magnet core 6 which forms a boss 7, penetrating the housing 1 and intended to be coupled to a fuel line 8 as shown. The soft iron magnet core 6 includes a flange 9 which also serves as a magnetic flux conductor to the housing to which it is fastened by a crimped rim 10 of the housing 1. Coaxial with and in juxtaposition to the soft iron core 6 is an armature 12 which is assembled by a press-fit connection with a valve needle 13. The valve needle slides longitudinally within a bore 15&#39; of a nozzle body 15 which is held in a reduced terminal portion of the housing 1 by a crimped rim 14. The valve needle is provided with lands 13a and 13b for guiding the valve needle during its longitudinal sliding movement within the bore 15&#39;. The valve needle is also provided with an axial bore 16, indicated by broken lines, which intersects with a transverse bore 17. Fuel supplied through the axial bore 16 flows radially into the nozzle body through the transverse bore 17, thence through longitudinal grooves 18 which are ground in the front part of the land 13b of the valve needle body, and then into the annular space 19 immediately adjacent to the valve seat of the valve needle. 
     The magnetic winding 4 may be electrically connected to an electric controller (not shown) by means of the connector pin 23 located in a molded-on plastic part 22. When the winding 4 receives a sufficient amount of excitation current from the controller, the armature 12 and the valve needle 13 can be attracted to the soft iron core 6 in opposition to the restoring force of the central closure spring 24. 
     The press-fit armature connection, indicated generally as 25, which serves as the positive operational connection between the valve needle 13 and the armature 12 is formed by a series of bulges or lands 26 spaced apart by grooves 32. These lands and grooves are formed at the appropriate needle end 27 which cooperates with the wall 28 of a bore 29 that is provided within the armature 12, all of which will be better understood by referring to FIG. 2. 
     In FIG. 2 the armature is shown as including an enlarged bore 29 into which the upper portion of the needle is positioned preparatory for the assembly operation. During assembly of the structure, a swaging ring 31 is drawn over the outer surface 30 of the armature 12 to reduce the inside diameter of the bore 29. In this process, the substantially softer armature material is pressed into the annular grooves 32 of the valve needle which produces a fixed, positive, operational connection between the valve needle and the armature. During this step of the manufacturing process, the valve needle 13 is located within a supporting jig 33. 
     In another preferred embodiment of the invention, the flow of fuel within the valve takes place over one or more flattened portions 34 above the region 27 of the valve needle 13 as shown in FIG. 2 instead of through bores 16 and 17 within the body of the valve needle as shown in FIG. 1. 
     It is to be understood, of course, that the assembly of the armature with the needle is conducted in such a manner that the swaging operation will not restrict flow of fuel in the manner described.