Internal-combustion engines – High tension ignition system – Having a specific ignition coil
Patent
1992-04-15
1994-05-31
Nelli, Raymond A.
Internal-combustion engines
High tension ignition system
Having a specific ignition coil
123598, 123605, 123620, F02P 1100
Patent
active
053159829
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION AND PRIOR ART
The present invention relates to ignition coils for ignition systems for igniting air-fuel mixtures, and particularly for use in systems using capacitors for storing higher levels of ignition energy, i.e. high energy capacitive discharge ignition systems, and for delivering the energy in the form of a rapidly pulsing (multi-strike) sequence of spark pulses.
Considerable research has been conducted on ignition systems for internal combustion engines for improving their capability to ignite air-fuel mixtures. More specifically, during the past few decades, there has been work done on improving the ability of ignition systems to ignite air-fuel mixtures with poor ignition characteristics, especially of the inherently cleaner and more efficiently burning leans air-fuel mixtures.
Much of the prior art work on so called high energy ignition has focussed on alternative approaches other than coil design for delivering high ignition energy. Little attention has been given to improving the actual coil design, particularly in view of the recent development of the high efficiency, voltage doubling, low turns ratio coil principle disclosed in U.S. Pat. No. 4,677,960 referred to hereinafter as the Voltage Doubling Coil principle, or Doubling principle for short.
Prior art work on spark ignition, including ignition coils, are numerous, and for example, are summarized in Edward F. Obert's book, "Internal Combustion Engines and Air Pollution", pp. 532 to 566, Spark-Ignition Engines, Intext Educational Publishers, 1973. The work reported by Obert, and the work published since then, including the coil design presented in the above patent, are based on well established principles of designing coils by either winding the primary and secondary windings essentially concentrically, or on different arms of a closed magnetic core for high leakage inductance. Included are various ways of performing the winding, especially the much longer secondary winding, and these are well known to one skilled in the art.
SUMMARY OF THE INVENTION
On the other hand, the present invention is based in part in a) recognizing that the open circuit (high voltage) and the closed circuit (high current) properties of ignition coils can be separated, especially for approaches based on the Doubling principle, and that each part of the coil is different and can be designed to be optimized separately from the perspective of minimizing resistive and core losses and core size and overall coil size, and b) acting effectively on the basis of such recognition.
Specifically, the effective constructions of two different core cross-sectional areas and core shapes are arrived at for the primary and secondary windings, the secondary requiring about half or less the core area of the primary depending in part on the output capacitance and core material to accomodate a larger winding area. Moreover, given that a high leakage inductance Lpe is preferred, i.e. of about 50 microhenries for an input capacitance Cp of about 5 microfarads, a preferred embodiment is developed in which the windings are placed axially side-by-side for easy containment in each half of pot or E type core, having low EMI, i.e. electromagnetic interference. As a further result, for a primary voltage Vp of 350 volts, a preferred design is possible with only about ten turns of primary winding (and 500 turns of secondary winding as per the Voltage Doubling principle).
As part of an overall optimized ignition system as disclosed in U.S. patent application Ser. No. 131,948, the present coil structure family (i.e. family of designs of such structures within the present invention) lends itself to a more optimally defined spark pulsing wave shape of the capacitive discharge circuit disclosed in that patent application, including the recharge circuit disclosed therein. Moreover, such new coil structures make possible further system optimization and extensions, as in distributorless ignition systems now made possible by the compact nature of the coil structures. For
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Redl Richard
Ward Michael A. V.
Cohen Jerry
Combustion Electromagnetics Inc.
Nelli Raymond A.
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