Patent Publication Number: US-6341412-B1

Title: Methods of forming a sheath and plastic ring on a electromagnetically operated valve

Description:
This application is a continuation of application Ser. No. 08/238,085 filed May 4, 1994 now abandoned, which is a division of Ser. No. 08/079,581 filed Jun. 22, 1993, abandoned, which is a division of Ser. No. 07/915,991 filed Aug. 3, 1992, now U.S. Pat. No. 5,275,341. 
    
    
     PRIOR ART 
     The invention is based on an electromagnetically operable valve as set forth hereinafter. 
     An electromagnetically operable valve has already been proposed in Patent Application P 38 25 135.3 U.S. Pat. No. 4,967,666, in which at least a part of the valve is surrounded by a plastic sheath, and on which an electrical connecting plug is integrally formed. However, different valve extrusion coating tools are required depending on the embodiment of the electrical connecting plug. This prevents cost-effective, flexible assembly. 
     ADVANTAGES OF THE INVENTION 
     The valve according to the invention has the advantage of simple production and assembly which permits cost-effective mass production since only a single valve extrusion coating tool is required for the different embodiments of the electrical connecting plug. As a consequence, this results in greater flexibility during assembly. Good handling capability of the plastic injection moulding, which consists of the magnet coil and the electrical connecting plug, can be named as a further advantage. 
     It is particularly advantageous to provide on the circumference of the inlet-side end of the fuel inlet connecting piece an annular groove whose radially extending side surfaces are formed by the plastic sheath surrounding a part of the valve, and whose groove base is formed by the circumference of the fuel inlet connecting piece. 
     It is also advantageous if an axial gap, in which there is arranged, by clamping-in, a non-magnetic stop plate which forms a residual air gap between the inlet-side end of the armature and the core end and which bounds the movement of the valve closing body during the valve opening process, is formed between the end surface of the core end facing the armature and a shoulder of the intermediate part. 
     It is likewise advantageous if the fuel inlet connecting piece exhibits a constant external diameter over its entire length. 
     It is particularly advantageous if the cylindrical valve seating body exhibits a constant external diameter. 
     A valve having the features set forth herein makes possible a compact, short structural shape of the valve. 
    
    
     DRAWING 
     An exemplary embodiment of the invention is shown in simplified form in the drawing and is explained in more detail in the following description. 
     FIG. 1 shows an exemplary embodiment of a valve designed according to the invention, and 
     FIG. 2 shows the independent plastic injection moulding which consists of the magnet coil and the electrical connecting plug. 
    
    
     DESCRIPTION OF THE EXEMPLARY EMBODIMENT 
     The electromagnetically operable valve, which is shown by way of example in FIG. 1, in the form of an injection valve for fuel injection systems of internal-combustion engines has a fuel inlet connecting piece  1 , which is surrounded by a magnet coil  4 , is used as a core and exhibits a constant external diameter, constructed for example by means of centreless grinding, over its entire length in order to make use of the space as well as possible. The magnet coil  4 , having a coil former  2 , is provided, as is shown in FIG. 2, with a plastic extrusion coating  7 , an electrical connecting plug  21  being injection moulded at the same time, so that an independent plastic injection moulding is produced which contains the magnet coil  4  and the connecting plug  21 . The magnet coil  4 , which in the radial direction exhibits a stepped coil former  2  having a winding  13  which is stepped in the radial direction, in conjunction with the fuel inlet connecting piece  1 , which exhibits a constant external diameter, makes possible a short and compact construction of the injection valve, as is explained in the following text. 
     A tubular metallic intermediate part  6  is closely connected to a lower core end  3  of the fuel inlet connecting piece  1 , concentrically with respect to a valve longitudinal axis  5 , by welding, and at the same time engages partially axially around the core end  3  by means of an upper cylindrical section  41 . The stepped coil former  2  engages partially around the fuel inlet connecting piece  1  and, by means of a step  42  having a larger diameter, a cylindrical section  41  of the intermediate part  6 . At its end facing away from the fuel inlet connecting piece  1 , the intermediate part  6  is provided with a lower cylindrical section A 33  which engages around a tubular connecting part  14  and is closely connected thereto by welding. A cylindrical valve seating body  8  is closely mounted into the downstream end of the connecting part  14  by welding. The arrangement in a row of the fuel inlet connecting piece  1 , the intermediate part  6 , the connecting part  14  and the valve seating body  8  thus represents a rigid metallic unit. The valve seating body  8  exhibits a constant external diameter, constructed for example by means of centreless grinding, so that the valve seating body  8  can be inserted completely into the connecting part  14  and improved sealing between the valve seating body  8  and the internal hole  30  in the connecting part  14  is achieved by means of the longer overlap. 
     An adjusting sleeve  20 , which is pushed into a flow bore  19  in the fuel inlet connecting piece  1 , exhibits a slot  31  in the longitudinal direction, and is formed for example out of rolled spring-steel sheet, is used for adjusting the spring pretensioning of a restoring spring  32  which abuts against the adjusting sleeve  20  and is supported downstream on a connecting pipe  11 . A tubular armature  12 , which is guided by a guide collar  15  of the intermediate part  6 , is connected by welding to the end of the connecting pipe  11  facing the restoring spring  32 . A valve closing body  10 , which interacts with the valve seat  9  of the valve seating body  8  and is constructed for example as a ball, is connected to the connecting pipe  11  by soldering or welding, at the other end of said connecting pipe  11 . At least one spray opening  33 , formed for example by erosion, is constructed downstream from the valve seat  9  in the valve seating body  8 . The welded seam  35  between the valve seating body  8  and the connecting part  14  is at a relatively large distance from the spray opening or openings  33  and from the valve seat  9 , so that an effect on the flow quantity and lack of sealing resulting from warping of the valve seating body  8  as a consequence of the high temperatures occurring during welding are effectively prevented. 
     An axial gap  29  in which there is arranged, by clamping-in, a non-magnetic stop plate  27  which forms a residual air gap between the inlet-side end  26  of the armature  12  and the end surface  23  of the core end  3  and which bounds the movement of the valve closing body  10  during the valve opening process, is formed between the end surface  23  of the core end  3  facing the armature  12  and a shoulder  24 , which leads to the upper cylinder section  41 , of the intermediate part  6 . Because of its relatively high bending stiffness, the clamped stop plate  27  protects the end surface  23  of the core end  3  against wear better than a loose plate, in which there is a risk of tilting or of stopping unevenly. 
     The magnet coil  4  is surrounded by at least one, guide element  16  which is constructed as a clip in the exemplary embodiment, is used as a ferromagnetic element, extends over the entire length of the magnet coil  4  in the axial direction, and at least partially surrounds the magnet coil  4  in the circumferential direction, and abuts against the fuel inlet connecting piece  1  at its one end and against the connecting part  14  at its other end, and is connected to said connecting piece  1  and connecting part  14  for example by welding. 
     The fuel inlet connecting piece  1  is provided with a retaining groove  46  close to the inlet end. A part of the valve is surrounded by a plastic sheath  18  which extends axially, originating from the fuel inlet connecting piece  1 . An annular plastic ring  48  is formed in the retaining groove  46  by the plastic sheath and the plastic sheath extends over the magnet coil  4  with the connecting plug  21  and the at least one guide element  16  and, at the same time, forms radially extending side surfaces of an annular groove  25  which is provided on the circumference of the inlet-side end  44  of the fuel inlet connecting piece  1  between one side surface  47  of the plastic ring  48  and a radially extending side surface  49  formed by an upper end of the plastic sheath  18 . The groove base of the annular groove  25  exhibits, for example, a sealing ring  45  which is retained between the side surfaces  47  and  49  of the retaining ring  48  and the radially extending side surface of the plastic sheath  18 , respectively. 
     The described plastic extrusion coating  7  of the magnet coil  4 , in conjunction with the connecting plug  21  which is injection moulded at the same time, permits high flexibility during assembly of valves of different construction, since only one extrusion coating tool is required to produce the plastic sheath  18  for connecting plugs  21  and magnet coils  4  of different design. The magnet coil  4 , which exhibits the coil former  2  which is stepped in the radial direction with the winding  13  which is stepped in the radial direction, makes possible a compact and short structural shape of the valve, in that said coil overhangs the upper cylindrical section  41  of the intermediate part  6  and hence produces an agglomeration of the individual parts. 
     The foregoing relates to a preferred exemplary embodiment of the invention, it being understood that other variants and embodiments thereof are possible within the spirit and scope of the invention, the latter being defined by the appended claims.