Patent Publication Number: US-2003234715-A1

Title: Ignition system coil assembly featuring flexible ring terminal interconnects

Description:
TECHNICAL FIELD  
       [0001] The present invention relates to automotive ignition systems, particularly the ignition coil assembly thereof. More particularly, the present invention relates to a flexible ring-shaped terminal for interfacing the secondary wire spool of the ignition coil to a respective tower terminal of the ignition system.  
       BACKGROUND OF THE INVENTION  
       [0002] Automotive ignition systems utilize an ignition coil for providing the high voltages necessary to induce sparking at the spark plugs. The ignition coil has a primary wire spool, referred to simply hereinafter as the “primary coil” and a secondary wire spool, referred to hereinafter simply as the “secondary coil”. The primary coil usually has an iron core to increase the magnetic field strength produced thereby, wherein pulsations in this magnetic field induce an applied electromotive force (EMF) in the secondary coil. Because the number of turns of the secondary coil is far greater than the number of turns of the primary coil, the voltage (for example 20 kV) of the EMF of the secondary coil is considerably higher than the input voltage (for example 12 V) of the primary coil.  
       [0003] Each of the spark plug wires of the ignition system connect to a respective tower terminal of the electrical system. In regard to this interconnection, the tower terminals are mounted to a dielectric (ie., plastic) base and are connected to the secondary coil. Each tower terminal has an exposed male pin terminal for snappingly interfacing with a female socket terminal of the spark plug wire.  
       [0004] The conventional secondary coil interconnect has a number of deficiencies, among these include an excessive area requiring large cross-sections of potting material; little protection from dendrite; excessive assembly steps; limited multiplicity of possible applications due to the secondary coil being non-symmetrical; specialization of the connection interface, which reduces options available for a common case envelope; and complications associated with the molds for the plastic components.  
       [0005] Accordingly, what remains needed in the art is an interconnection interface between the secondary coil and the tower terminals of an automotive ignition system which has none of the above described deficiencies.  
       SUMMARY OF THE INVENTION  
       [0006] The present invention is a coil assembly featuring flexible ring terminals for providing interconnections between a secondary coil and tower terminals of, for example, an automotive ignition system, the ignition coil assembly having the advantages of: the possibility of multiple applications in that the secondary coil may be symmetrical, and the case may be configured common among the applications; minimization of cross-section and, therefore, minimization of potting; elimination of sharp edges, thereby eliminating dendrite; simple and few assembly operations; and simplification of the components.  
       [0007] The flexible ring terminal according to the present invention has a hollow cross-sectioned annular configuration, wherein the electrically conductive ring terminal sidewall has a discontinuity for facilitating resilient flexing.  
       [0008] In a first embodiment, the sidewall defines a hollow cross-section characterized by left and right arcuate ends, an annular apex at an outer face, an inner face having an annular slot formed therein, wherein the annular slot is located adjacent one of the arcuate ends.  
       [0009] In a second embodiment, the sidewall defines a hollow cross-section defined by an inner face, an arcuate end, and an outer face connected to the inner face by the arcuate end, wherein opposite the arcuate end the outer face is shaped so that an end portion thereof abuts an end portion of the inner face. In a third embodiment.  
       [0010] In a third embodiment, the sidewall defines a hollow cross-section characterized by left and right arcuate ends, an annular apex at an outer face, an inner face having an annular slot formed therein, wherein the annular slot is located medially between the arcuate ends.  
       [0011] In a fourth embodiment, the sidewall defines a hollow cross-section defined by an inner face, an arcuate end, and an outer face connected to the inner face by the arcuate end, wherein opposite the arcuate end the outer face is shaped so that a bent-back end portion thereof abuts a bent-back end portion of the inner face.  
       [0012] The ring terminal is slipped onto an end of a tube, wherein preferably a ring terminal is slipped onto each of the opposed ends of the tube, and wherein the tube carries the secondary coil. Each end of the secondary coil is connected to a respective flexible ring terminal. A coil package is collectively formed of the tube with its secondary coil, the flexible ring terminals and a concentrically disposed primary coil (and its ferromagneitc core). The coil package is slipped into a cylindrical coil receptacle of a dielectric (ie., plastic) case. The tube has an annular locating abutment near each end which positions the tube within the coil receptacle.  
       [0013] The case carries a tower terminal for each ring terminal, wherein the contact surface of each tower terminal respectively contacts its ring terminal. In this regard, the ring terminals are resiliently compressed so as to apply contact pressure with respect to the contact surface of each of the tower terminals. The case further has a tower terminal receptacle respectively for each tower terminal such that an exposed male pin terminal of each tower terminal is snappingly interfaced with a female socket terminal of a respective spark plug wire.  
       [0014] Accordingly, it is an object of the present invention to provide a flexible ring shaped interconnection between a secondary coil and one or more tower terminals.  
       [0015] It is an additional object of the present invention to provide a coil assembly of an ignition system, the coil assembly featuring a flexible ring shaped interconnection between its secondary coil and one or more tower terminals thereof.  
       [0016] These and additional objects, features and advantages of the present invention will become clearer from the following specification of a preferred embodiment. 
     
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
     [0017]FIG. 1 is a partly sectional side view of a coil assembly according to the present invention, wherein a flexible ring terminal according to a first embodiment of the present invention is depicted.  
     [0018]FIG. 2 is an end view seen along line  2 - 2  of FIG. 1.  
     [0019]FIG. 3 is a perspective view of the flexible ring terminal depicted at FIGS. 1 and 2.  
     [0020]FIG. 4 is a sectional view of the flexible ring terminal seen along line  4 - 4  of FIG. 3.  
     [0021]FIG. 5A is a perspective view of a second embodiment of a flexible ring terminal according to the present invention.  
     [0022]FIG. 5B is a top plan view of the flexible ring terminal of FIG. 5A.  
     [0023]FIG. 5C is a sectional view seen along line  5 C- 5 C of FIG. 5A.  
     [0024]FIG. 6A is a perspective view of a third embodiment of a flexible ring terminal according to the present invention.  
     [0025]FIG. 6B is a sectional view seen along line  6 B- 6 B of FIG. 6A.  
     [0026]FIG. 7A is a perspective view of a fourth embodiment of a flexible ring terminal according to the present invention.  
     [0027]FIG. 7B is a sectional view seen along line  7 B- 7 B of FIG. 7A. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT  
     [0028] Referring now to the Drawing, FIGS. 1 and 2 depict an example of an ignition system coil assembly  10  according to the present invention. The coil assembly  10  includes a dielectric (for example, plastic) case  12  having a cylindrical coil receptacle  14  and a pair of tower terminal receptacles  16 ,  18 . The coil assembly  10  further includes a pair of tower terminals  20 ,  22  partly embedded in the case  12 , wherein one tower terminal is respectively located at each tower terminal receptacle  16 ,  18  such that a contact surface  24  is exposed at the coil receptacle  14  and a male pin terminal  26  is exposed in its respective tower terminal receptacle such that a female socket of a spark plug wire may be snapped respectively thereupon in a manner well known in the art.  
     [0029] The coil assembly  10  further includes a coil package  28 , which, in turn, includes a dielectric (for example, plastic) tube  30 ; a secondary coil  32  wound on the tube; a pair of flexible ring terminals  34  mounted upon the tube at respectively opposing ends thereof; and a primary coil  38  disposed concentrically inside the tube, wherein the primary coil typically includes a ferromagnetic core. The secondary coil  32  has a larger number of turns than the primary coil  38  dependent upon the voltage step-up desired.  
     [0030] Operatively, the primary coil  38  is connected to an interrupting source of low voltage which produces a pulsating magnetic field through the secondary coil  32  such as to thereby create an induced EMF in the secondary coil. The EMF provides a very high voltage in the secondary coil sufficient to achieve spark plug sparking. In this regard, each of the male pin terminals  26  is snappingly connected to a respective female socket of a spark plug wire, wherein each spark plug wire is connected, in turn, to a spark plug.  
     [0031] A key aspect of the present invention is the interface of the secondary coil  32  with the tower terminals  20 ,  22  via the electrically conductive flexible ring terminals  34 . The flexible ring terminals  34  have an annular shape with an inside circumference for snuggly fitting upon the cylindrical shape of the tube  30 . Each flexible ring terminal  34  has a sidewall  36  providing an annular hollow H, wherein an annular discontinuity D is formed in the sidewall which allows for a resilient compressibility of the sidewall in the radial direction.  
     [0032] The placement of the tube  30  into the coil receptacle  14  is accompanied by the flexible ring terminals  34  compressing against the receptacle wall  14   w , as well as against the contact surface  24  of the respective tower terminals  20 ,  22 . In this regard, the tube  30  is provided with annular locating abutments  40 ,  42 , one abutment near each end, which serve to abut the receptacle wall  14   w  and thereby centrally locate the tube with respect to the coil receptacle. The locating abutments  40 ,  42  may also serve to aid locating of the flexible ring terminals with respect to the tube, and thereby, with respect to the contact surfaces  26 . Each of the flexible ring terminals  34  are electrically connected to a respective end of the secondary coil via a respective shunt  44 ,  46 , each shunt passing respectively through a passage  48  formed in the locating abutments  40 ,  42 .  
     [0033] Four preferred examples of configuration of the flexible ring terminals  34  are presented hereinafter, the first being most preferred.  
     [0034] In a first embodiment of a flexible ring terminal  34 , as shown at FIGS. 1 through 4, a sidewall  36  defines a hollow H characterized by left and right arcuate ends  52 ,  54 , an annular apex  56  at an outer face  58 , an inner face  60  having an annular discontinuity D in the form of an annular slot  62  formed in the inner face, wherein the annular slot is located adjacent one of the arcuate ends  54 . At the slot  62 , the sidewall edge  64  at both sides of the slot are turned inwardly. In operation as shown at FIG. 1, the inner face  60  abuts the tube  30  and the annular apex  56  abuts the contact surface  26 .  
     [0035] In a second embodiment of a flexible ring terminal  34 ′, as shown at FIGS. 5A through 5C, a sidewall  36 ″ defines a hollow H″ characterized by an inner face  68 , an arcuate end  70 , and an outer face  72  connected to the inner face by the arcuate end. Distally from the arcuate end  70 , the outer face  72  has an S-shaped contour  74  such that an end portion  76  thereof abuts an end portion  78  of the inner face  68 . In this case, the annular discontinuity D′ is in the form of the unattached abutment of the end portions  76 ,  78 . In operation, the inner face  68  abuts the tube  30  and the outer face between the arcuate end  70  and the S-shaped contour abuts the contact surface  26 .  
     [0036] In a third embodiment of a flexible ring terminal  34 ″, as shown at FIGS. 6A and 6B, a sidewall  36 ″ defines a hollow H″ characterized by left and right arcuate ends  82 ,  84 , an annular apex  86  at an outer face  88 , an inner face  90  having an annuklar discontinuity D″ in the form of an annular slot  92  formed in the inner face, wherein the annular slot is located medially between the arcuate ends. At the slot  92 , the sidewall edge  94  at both sides of the slot are turned inwardly. In operation, the inner face  90  abuts the tube  30  and the annular apex  86  abuts the contact surface  26 .  
     [0037] In a fourth embodiment of a flexible ring terminal  34 ′″, as shown at FIGS. 7A and 7B, a sidewall  36 ′″ defines a hollow H′″ characterized by an inner face  98 , an arcuate end  100 , and an outer face  102  connected to the inner face by the arcuate end. Distally from the arcuate end  100 , the outer face  102  has an S-shaped contour  104  such that a bent-back end portion  106  thereof abuts a back-bent end portion  108  of the inner face  98 . In this case, the annular discontinuity D′″ is in the form of the unattached abutment of the bent-back end portions  106 ,  108 . In operation, the inner face  98  abuts the tube  30  and the outer face between the arcuate end  100  and the S-shaped contour abuts the contact surface  26 .  
     [0038] To those skilled in the art to which this invention appertains, the above described preferred embodiment may be subject to change or modification. Such change or modification can be carried out without departing from the scope of the invention, which is intended to be limited only by the scope of the appended claims.