Abstract:
A method and apparatus for securing at least one ignition coil to an ignition coil cassette, the ignition coil cassette having a main body portion being adapted to receive and engage a plurality of coils for generating a high voltage signal to be received by a spark plug of an internal combustion engine. The coils being ultrasonically welded to the main body portion of the ignition coil cassette. The coils being secured in a manner which correctly positions the coils in an appropriate location as well as providing a rigid securement of the coil to the main body portion.

Description:
TECHNICAL FIELD  
         [0001]    The present application relates to an ignition coil cassette having a plurality of coils for an internal combustion engine. More particularly, the present application relates to an ignition coil cassette and method of joining the ignition coils to the cassette.  
         BACKGROUND  
         [0002]    An ignition system for an internal combustion engine provides spark to engine cylinders in a controlled manner. Some ignition systems include spark plugs, a high voltage coil and a distributor that directs high voltage power through spark plug wires to the spark plugs. Distributorless systems rely upon microprocessors to more precisely control engine operation. In such systems, the distributor is eliminated and a microprocessor controls engine operation based upon data generated as a result of engine operation.  
           [0003]    Systems which utilize a distributor only require a single coil for four, six or eight cylinders, while a distributorless ignition system, utilizes a plurality of coils, for example, one coil to develop a high voltage output for each spark plug.  
           [0004]    In addition, and in a distributorless system, modular groups of ignition parts connect an ignition coil or coils to several spark plugs simultaneously. A single unit can be provided to house the components of an ignition system. The single unit provides advantages when servicing an ignition system. A mass produced part can be quickly removed and replaced. The replacement part can be fully checked for purposes of quality control resulting in improved reliability and customer service.  
           [0005]    A single distribution cassette including a plurality of coils requires the components to be sealed within the unit to protect the individual components from deterioration due to moisture or operation under harsh conditions.  
         SUMMARY  
         [0006]    An ignition coil cassette, having a main body portion with a plurality of openings for receiving a plurality of coils, the plurality of coils are ultrasonically welded to the main body portion and provide a high voltage signal to spark plugs of an internal combustion engine.  
           [0007]    An apparatus for securing a plurality of coils to an ignition coil cassette, the apparatus includes a cassette support for supporting a main body portion of the cassette and the cassette support maintains the position of the main body portion during the securement of the coil. A fixture support having a guide pin for aligning the coil with respect to the main body portion, the guide pin is adjustable with respect to the entire fixture moves to shuttle each coil under the ultrasonic weld horn for welding. The apparatus includes an ultrasonic welding machine for welding the coils to the cassette.  
           [0008]    A method for producing an ignition coil cassette, including: inserting a coil through an aperture in a body portion of the ignition coil cassette; and ultrasonically welding the coil to the body portion.  
           [0009]    The above-described and other features and advantages of the present invention will be appreciated and understood by those skilled in the art from the following detailed description, drawings, and appended claims. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0010]    [0010]FIG. 1 is a perspective view of a coil assembly constructed in accordance with an exemplary embodiment of the present invention;  
         [0011]    [0011]FIG. 2 is a partial perspective view of a coil assembly constructed in accordance with an exemplary embodiment of the present invention;  
         [0012]    [0012]FIG. 3 is a view along lines  3 - 3  of FIG. 1;  
         [0013]    [0013]FIG. 4 is a cross-sectional view of a portion of a coil assembly constructed in accordance with an exemplary embodiment of the present invention;  
         [0014]    [0014]FIG. 5 is a cross-sectional view illustrating a portion of the assembly process in accordance with an exemplary embodiment of the present invention; FIG. 6 is a partial cross-sectional view of an apparatus for producing a coil assembly in accordance with an exemplary embodiment of the present invention; and  
         [0015]    [0015]FIG. 7 is a cross-sectional view of an apparatus for producing a coil assembly in accordance with an exemplary embodiment of the present invention. 
     
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT  
       [0016]    Referring now to FIGS.  1 - 4 , a cassette  10  constructed in accordance with an exemplary embodiment of the present invention is illustrated. In an exemplary embodiment, cassette  10  is constructed out of a lightweight, easily moldable material such as plastic or polymers.  
         [0017]    Cassette  10  includes a main body portion  12 . Main body portion  12  includes a plurality of coil openings  14  for receiving and securing a plurality of coils  16 . In an exemplary embodiment, cassette  10  includes four coil openings for receiving four coils. Of course, cassette  10  can be configured to have more or less than four coils.  
         [0018]    Each coil  16  and main body portion  12  is manufactured separately. Alternatively, coil  16  can be configured for securement to a spark plug of an internal combustion engine. Of course, other coil configurations may be used with cassette  10 .  
         [0019]    Main body portion  12  is further defined into a lower body portion  18  and an upper body portion  20 . Upper body portion  20  defines an area  22 . In an assembled state, area  22  is enclosed within upper body portion  20  of cassette  10  by an encapsulant material  24  that is filled into upper body portion  20  after assembly of coil  10  is complete including the connection of the necessary electronics to the coils. In accordance with an exemplary embodiment of the present invention encapsulant  24  is an epoxy, resins, hard gels, polyurethane, silicon gel or other material capable of filling in area  22  and encapsulating the component parts of cassette  10  within area  22 .  
         [0020]    Encapsulant  24  must be able to withstand the harsh environment of an engine compartment after it has cured.  
         [0021]    Area  22  is configured to run along the length of main body portion  20  and allows access to coil openings  14  and coils  16 . In addition, a plurality of electrical connectors  26  are located at an end portion  28  of upper body portion  20 . Plurality of electrical connectors  26  are in electrical communication with coils  16  as well as an engine control module for controlling high voltage output of coils  16 .  
         [0022]    In addition, a circuit board  29  or electronics for communication with coil  16  and connects  26  is placed within area  22 . Alternatively circuit board  29  is a plurality of electrical connectors. Circuit board  29  is inserted into area  26  after coils  16  has been secured to main body portion  12 .  
         [0023]    Cassette  10  is configured to have a pair of openings  30  for securing cassette  10  to an appropriate location within an engine compartment of a vehicle (not shown). Openings  30  pass through encapsulant  24  as well as main body portion  12 . In an exemplary embodiment, openings  30  are positioned between the outermost coil and its adjacent coil.  
         [0024]    Openings  30  contains metal bushings  31  rigidly attached to the cassette. The bushings allow the cassette to be bolted to the engine. As an alternative, the bushings can be welded or molded into cassette  10 .  
         [0025]    In addition, and as yet another alternative, the bushings and openings are randomly positioned as dictated by the engine configuration. Moreover, the number of openings and associated bushings may also vary.  
         [0026]    Referring now to FIGS.  4 - 6 , the securement of coils  16  to main body portion  12  is illustrated. Each coil  16  is inserted into area  22  and into coil opening  14  of main body portion  12  until an upper flange portion  32  of coil  16  rests upon a shoulder portion  34  of coil opening  14 .  
         [0027]    The configuration of the weld horn allows it to make contact with flange  32 . This allows the weld horn to cover a plastic flash (e.g. particles or debris) that may occur during the welding process. Accordingly, the plastic flash is melted into the weld joint.  
         [0028]    In addition, and referring now in particular to FIG. 6, an apparatus  40  for the securement of coil  16  to main body portion  12  is illustrated. In an exemplary embodiment, apparatus  40  includes an ultrasonic welding device  42  comprising an ultrasonic horn  44  for making contact with a portion of coil  16 . In an exemplary embodiment, ultrasonic welding device  42  is a 20 kHz machine. Of course, other machines are contemplated for use in accordance with the present invention.  
         [0029]    Main body portion  12  of cassette  10  is supported and secured to a cassette support  46 . Cassette support  46  includes an opening  48  or means for allowing the insertion of coil  16  through coil opening  14  in main body portion  12 . Cassette support  46  prevents movement of main body portion  12  while coil  16  is being ultrasonically welded to main body portion  12 .  
         [0030]    During the welding procedure the ultrasonic horn is lowered downwardly until it contacts the coil. When a preset force of 10 or more pounds is met, the ultrasonic energy is activated melting be plastic weld interface and pushing the coil down to a predetermined stop. Of course, and as applications may vary, the amount of preset force may be lesser or greater than 10 pounds. Once the horn has reached the predetermined position the ultrasonic welding process stops.  
         [0031]    Apparatus  40  also includes an alignment pin  50  for providing a means for aligning coil  16  as it is inserted through coil opening  14 . The alignment of coil with respect to main body portion  12  is critical as in accordance with an exemplary embodiment, a plurality of coils are secured to main body portion  12  and once assembled cassette  10  must be configured to have each of the coils align with a plurality of spark plugs or spark plug openings.  
         [0032]    Thus, apparatus  40  also provides an alignment feature as well as a means for securing coils  16  to main body portion  12 .  
         [0033]    In an exemplary embodiment, alignment pin  50  protrudes outwardly from an alignment pin opening  52  in a fixture support  54 . A spring or other resilient member  56  is positioned within pin opening  52  in order to provide a biasing force to pin  50  in the direction of arrow  58 .  
         [0034]    Pin  50  can also move in a Z-direction (as illustrated in FIG. 6) only during the welding process. It can be adjusted in the X and Y directions during the process set up by adjusting member  54 .  
         [0035]    In addition, pin  50  has a tapered end portion  60  for locating the inside diameter of coil  16 . Since pin  50  does not travel very far into the inner portion of coil  16 , the tapered end portion helps to maintain coil  16  in the appropriate location during the welding process.  
         [0036]    Also, due to the shrinkage of encapsulant  24  and the warpage of main body portion  12  (e.g. during molding) there needs to be some adjustment of the pin  50  in the X and Y directions to ensure proper positioning of coils  16  over the spark plugs in the final product.  
         [0037]    Referring now to FIGS.  1 - 3  and FIG. 6 it is noted that coils  16  are secured to main body portion  12  prior to the securement of an end covering portion  62  to coils  16 . End covering portion  62  is constructed out of a nonconductive flexible material such as rubber. Accordingly, end covering portion  62  is not capable of providing a rigid means for supporting coil  16  as it is ultrasonically welded to main body portion  12 .  
         [0038]    Thus, each coil is secured to main body portion  12  prior to the securement of end portions  62 . Each coil  16  has an end portion  64  with a reduced inner diameter as well as components  63  of coil  16 . Thus, there is a small gap  65  within end portion  64 . Accordingly, and in order to provide the proper amount of support to coil  16  as it is ultrasonically welded to cassette  10  the end portion of alignment pin  50  is configured to have a tapered end. In addition, spring  56  allows pin  50  to move in the Z direction or vertically as coil  16  is secured to main body portion  12 .  
         [0039]    In an exemplary embodiment, a fixture  54  is configured to have four pins corresponding to the four coils being secured to the cassette body portion. Accordingly, and during the welding process, fixture  46  and  54  are capable of being slid or move in the X and Y directions in order to place each coil underneath the ultrasonic welding apparatus. This movement may be facilitated manually or by mechanical apparatus such as a motor, which may be driven by a controller having an operating algorithm.  
         [0040]    Alternatively, apparatus  40  may be configured to support and retain a cassette having more or less than four coils. In yet another alternative, the ultrasonic welding device  42  may be configured for movement in the X and Y direction. In yet another alternative, a plurality of ultrasonic welding devices may be employed (e.g. one for each coil).  
         [0041]    After all of the coils are secured to the cassette, area  22  is covered with an encapsulant in order to cover the electrical components of the same. Accordingly, the seal between main body portion  12  and coils  16  must be tight enough to prevent any leakage into the cassette. In addition, the strength of the seal between the coils and a cassette must be rigid enough to survive the potting process as well as the operating tolerances the cassette is exposed to.  
         [0042]    In summation, the method of ultrasonically welding the coils to the cassette in accordance with an exemplary embodiment ensures that there is a good seal between the coils and the cassette in addition to providing a strong enough structure to survive through the process steps required prior to the cassette potting (e.g. application of encapsulant). Additionally, this method controls the location of the high voltage tower of the coils with respect to the mounting bushings that are attached to the cassette.  
         [0043]    The individual coils are assembled and potted prior to the assembly of the cassette. The coils are loaded into a fixture that controls the location of the mounting bushings and the high voltage end of the coils. The part of the fixture controlling the coil position is spring biased and allows movement in a vertical direction.  
         [0044]    At the end of the welding operation the tolerance of the coil to a datum plane that goes through the bottom of the mounting bushings is kept to a low value (e.g. the tolerance of the fixture). The interference between the coils is a shear joint design. This allows the coils to take the necessary location before the plastic resolidifies and allows for a hermetically sealed joint.  
         [0045]    While the invention has been described with reference to an exemplary embodiment, it will be understood by those skilled in the art that various changes may be made and equivalents may be substituted for elements thereof without departing from the scope of the invention. In addition, many modifications may be made to adapt a particular situation or material to the teachings of the invention without departing from the essential scope thereof. Therefore, it is intended that the invention not be limited to the particular embodiment disclosed as the best mode contemplated for carrying out this invention, but that the invention will include all embodiments falling within the scope of the appended claims.