Abstract:
A coil winding system is provided for making a secondary winding for an automotive ignition coil. The system includes a roller configured to apply a holding force to wire being dispensed from a wire nozzle onto a bobbin. The nozzle and roller are moved by a drive mechanism under control of a controller from one axial end to the other axial end of the bobbin for winding the bobbin in a progressive winding fashion. The roller allows an increase in the winding angle of the layers, which reduces the voltage difference between adjacent layers, thereby reducing incidence of dielectric break down in that region.

Description:
BACKGROUND OF THE INVENTION  
         [0001]    1. Technical Field  
           [0002]    The present invention relates generally to the field of engine ignition coils, and, more particularly, to a system and method for winding an ignition coil.  
           [0003]    2. Description of the Related Art  
           [0004]    It is known to use an automated winding system for the manufacture of ignition coils wherein the system has a plurality of spindles for receiving empty coil spools or bobbins, as seen by reference to U.S. Pat. No. 5,950,956 issued to Yukitake. Yukitake discloses an ignition coil winding machine capable of simultaneously forming a plurality of engine ignition coils. The machine has a driver for rotating a shaft on which a coil bobbin is disposed, all under the control of a controller. The machine further includes a tensioning device in between a wire spool (containing wire destined for being wound on the bobbins) and a nozzle. The nozzle reciprocates in the coil winding direction, thereby laying out the wire on the bobbin according to a method specified in the Yukitake patent.  
           [0005]    It is also known to provide an ignition coil of the type suitable for mounting directly above the spark plug, sometimes referred to as a “pencil” coil, that employs a progressive wound secondary winding, as set forth in U.S. Pat. No. 6,276,348 issued to Skinner et al. entitled “IGNITION COIL ASSEMBLY WITH SPOOL HAVING RAMPS AT BOTH ENDS THEREOF.” As disclosed in Skinner et al., a progressive winding is a one segment winding where a “top” layer advances under an angle from one end of the spool to the other. The winding angle is important in such a configuration because it sets the voltage difference between adjacent layers. In current, conventional pencil coils, a typical winding angle ranges between about 8-12 degrees. Increasing the winding angle, however, has been heretofore limited by the wire collapsing at the bottom of the winding. Increasing the winding angle would be beneficial inasmuch as it would be reduce the voltage difference between adjacent wire layers, thereby decreasing the risk of failure due to voids produced in the secondary winding area. That is, in a conventional pencil coil, the secondary winding region is encapsulated with a dielectric material, such as an epoxy potting material. Increased voltage differences may break down such dielectric material, thereby allowing a short circuit between turns.  
           [0006]    There is therefore a need for an improved winding system that minimizes or eliminates one or more of the problems as set forth above.  
         SUMMARY OF THE INVENTION  
         [0007]    One advantage of the present invention is that it solves one or more of the problems set forth above. Another advantage of the present invention is that it facilitates manufacture of a progressive wound coil having an increased winding angle, which reduces a voltage difference between adjacent layers, thereby reducing the occurrence of dielectric break down and possible coil failure. In addition, the invention provides an improved robustness of the winding due to a reduction or elimination of the occurrence of wire movement during the winding process.  
           [0008]    In accordance with the present invention, a method is provided for winding a bobbin having a main axis to form a coil. The method comprises the step of holding the wire being wound on the bobbin in place using a roller. Accordingly, increased winding angles can be employed inasmuch as the wire layers need not rely solely on the tension in the wire during winding to maintain placement, but also benefits from the force exerted by the roller to keep the wire in place.  
           [0009]    In a preferred embodiment, the roller comprises an outer surface formed of a material having a predetermined hardness (or pliability, as the case may be), for example, rubber having a preselected durometer. In a still further preferred embodiment, the outer surface of the roller is formed so as to have a predetermined pattern configured to facilitate holding the wire in place.  
           [0010]    In another aspect of the invention, a system for winding a bobbin is also presented.  
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0011]    Additional objects and advantages of the present invention will be more readily apparent from the following detailed description of preferred embodiments thereof, when taken together with the accompanying drawings in which:  
         [0012]    [0012]FIG. 1 is a simplified block diagram view of a winding system according to the present invention;  
         [0013]    [0013]FIG. 2 is a partial, perspective view showing the winding system of FIG. 1 in a multi-spindle configuration;  
         [0014]    [0014]FIG. 3 is a simplified cross-sectional view of a bobbin being wound using a progressive winding strategy; and  
         [0015]    [0015]FIG. 4 is a simplified cross-sectional view of the bobbin of FIG. 3 enlarged, showing use of a roller according to the invention.  
         [0016]    [0016]FIG. 5 is a simplified side view of an alternate preferred embodiment. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0017]    Referring now to the drawings wherein like reference numerals are used to identify identical components in the various views, FIG. 1 shows a winding system  10  in accordance with the present invention. Winding system  10  includes a main controller  12 , a dereeler assembly  14 , and a base with a drive portion  16  that includes one or more spindles  18  and corresponding number of nozzles  20 . The basic winding system  10  (exclusive of a roller  40  to be described below) is generally of a conventional nature and may be any one of a number of commercially available systems. For example, a multi-spindle coil winding machine (exclusive of roller  40  and the accompanying software functionality to be described in detail hereinafter), may be obtained from Prosys Industries, Inc., Plymouth, Mich., USA or Marsilli, for example only. FIG. 1 further illustrates an ignition coil bobbin  22 , a wire feed assembly  24  comprising wire  26  contained on spool  28 . In alternate embodiments, the winding system  10  may comprise a single-spindle winder, a fly type winder (i.e., post for receiving bobbin does not move but winding head does), an insertion type winder, an armature type winder, and a yolk type winder.  
         [0018]    [0018]FIG. 2 illustrates the drive portion  16  of machine winding system  10  in greater detail. As shown in FIG. 2, winding system  10  is of the type that is capable of simultaneously winding at least one, and for example, a plurality of bobbins  22   1 ,  22   2 , . . . ,  22   i  respectively mounted to spindles  18   1 ,  18   2 , . . . ,  18   i . Corresponding parallel structure such as nozzles  20   1 ,  20   2 , . . . ,  20   i , and dereeler assemblies  14   1 ,  14   2 , . . . ,  14   i  are operative to feed respective runs of wire  26   1 ,  26   2 , . . .  26   i  for winding ignition coils. As also shown, corresponding parallel structure also includes a plurality of rollers  40   1 ,  40   2 , . . .  40   i  to facilitate holding the wire in place as it is being dispensed and wound onto the bobbins.  
         [0019]    With continued reference to FIG. 1, generally, wire  26  is drawn from spool  28  and is fed through dereeler  14 , which may provide a tensioning and/or take-up function relative to the wire  26 . Drive portion  16  is configured, generally, to rotate spindle  18  containing bobbin  22 , and, further, to reciprocate nozzle  20  over a preprogrammed axial length over bobbin  22 . Drive portion  16  operates in accordance with control signals received from and generated by controller  12 . Nozzle  20  can be moved by drive portion  16  axially with respect to spindle  18 , as well as being rotated, all as known to one of ordinary skill in the art. Roller  40 , generally, is moved in a manner corresponding to the movement of nozzle  20 , preferably, in synchronism therewith. Roller  40  is operative to hold the wire in place as it is being dispensed onto the bobbin  22 .  
         [0020]    Through the foregoing, a variety of coils having desired winding patterns may be made. In a preferred embodiment, the coil may be a primary or secondary coil of an ignition coil for an engine, such as an automotive engine. It should be understood that the invention may be used for many other types of winding patterns and coil types.  
         [0021]    [0021]FIG. 3 is a simplified cross-sectional view showing the winding process for one bobbin  22  in greater detail. In one embodiment, bobbin  22  comprises a secondary winding bobbin for use in an ignition coil (i.e., a “pencil” coil) for an internal combustion engine. The bobbin  22  is substantially cylindrical and extends along a main axis  34 , and has opposing first and second axial ends  30  and  32 . A winding bay is defined between tapered surfaces of winding flanges located at axial ends  30 , and  32 . As further illustrated in FIG. 3, in accordance with one embodiment of the present invention, a progressive winding approach is taken wherein wire  26  is set down in layers that move from one axial end (e.g., end  30 ) to the other axial end (e.g., end  32 ). As further shown, to achieve the progressive wound secondary winding, nozzle  20  moves axially, as described above. As shown in FIG. 3, nozzle  20  is shown in a first intermediate axial position  36 , and a second intermediate axial position  38  between its beginning axial position and ending axial position near ends  30 ,  32 , respectively. It should be understood, however, that the tapered ends are not needed for the present invention.  
         [0022]    [0022]FIG. 4 is an enlarged view of a portion of FIG. 3 showing, in greater detail, the winding process according to the present invention. Bobbin  22  at axial end  30  includes a winding flange  39  that is tapered at a predetermined angle, designated θ relative to a horizontal axis  41 . Horizontal axis  41  is substantially parallel to main axis  34  of bobbin  22 . In one embodiment, angle θ is equal to or greater than about 13°, and less than or equal to about 90°.  
         [0023]    Roller  40  is oriented, by way of connection to drive  16 , so that its axis of rotation  42  is substantially parallel to the tapered winding surface of flange  39 . Roller  40  is configured to apply a pressure, designated by vector  43  is FIG. 4, so as to hold wire  26  in place on spool  22  while nozzle  22  dispenses the same. Controller  12  is configured to move roller  40  in nozzle  20 , relative to bobbin  22 , from one axial end (e.g., end  30 ) to the other axial end (e.g., end  32 ) in a predetermined relationship, preferably, in synchronism.  
         [0024]    For example, as shown in FIG. 4, roller  40  is moved from a first axial position  44  to a second, intermediate axial position  46 . The roller would be moved by drive  16  under control of controller  12  all the way to end  32  of bobbin  22 . It would then be programmed to move radially outwardly as the last layers of the winding are dispensed onto bobbin  22 .  
         [0025]    Roller  40 , as mentioned above, is configured to rotate about its own axis of rotation  42 . In the embodiment of FIG. 4, the roller  40  is generally cylindrical in shape, with tapered ends. However, other shapes may be used. In addition, roller  40  is provided with an outer surface formed of a material having a predetermined hardness. In one embodiment, roller  40  has an outer surface comprising a rubber material having a pliability within a preselected range. In alternate embodiments, roller  40  would be formed so that an outer surface thereof has a predetermined texture configured to facilitate holding wire  26  in place during winding.  
         [0026]    [0026]FIG. 5 shows an alternate preferred embodiment of system  10 , designated  10   a  in the drawing. In this alternate embodiment, an alternate shaped roller, designated roller  40   a , is provided. Spool  40   a  is generally frusto-conical in shape, with an outer surface that tapers radially inwardly, as taken axially along axis  42   a  toward spool  22 . Winder guide needle  20  and roller  40   a  move in direction  48  along the length of spool  22 , just as described above for the first embodiment. In still other embodiments, multiple rollers may be employed around the circumference of bobbin  22 .  
         [0027]    It should be understood that the nozzle  20 , while not shown in FIG. 4, will typically be disposed normal to the paper (either above the paper, or into or behind the paper) and roller  40 .