Internal-combustion engines – High tension ignition system – Power supply – ignition coil primary – and interrupter element...
Patent
1992-09-30
1993-11-30
Nelli, Raymond A.
Internal-combustion engines
High tension ignition system
Power supply, ignition coil primary, and interrupter element...
123620, F02P 312
Patent
active
052655806
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
The present invention relates to a high voltage switch, and, more particularly, to a high voltage switch for use in a double-coil ignition system.
The invention is based on an ignition system e.g. as is known from DE-OS 37 31 393. High-voltage switches which are arranged on the secondary side, preferably in the spark plug terminal, are used in the above-mentioned ignition system. State-charging or breakdown diode cascades are used as high-voltage switching elements. Ten to fifty diodes are stacked one on top of the other depending on the electric strength of an individual diode and depending on the desired breakdown voltage. This kind of high-voltage switch which changes suddenly from the blocking state to the conducting state makes it possible to eliminate the influences of shunts at the spark plug. Because of their self-capacitance, long ignition lines following the breakdown diode have disadvantageous effects on the steepening effect of the breakdown diode. For this reason the high-voltage switch is preferably arranged in the spark plug terminal. When such semiconductor switching elements are used with double ignition coils, the breakdown voltage must be kept low enough so that it is achieved in every case because of the division of voltage on the secondary side. However, this has the disadvantage that there is hardly any steepening effect when the breakdown voltage clearly lies below 11 kV.
The present solution endeavors to find a favorable size of the breakdown voltage with respect to the greatest possible steepening effect for optimum use of the high-voltage switch.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide an improved double-coil ignition system having none of the above-described disadvantages.
This object and others which will be made more apparent hereinafter is attained in an ignition system for an internal combustion engine with semiconductor switching elements arranged in a secondary circuit of this ignition system, each semiconductor switching element comprising at least one breakdown diode connected so that the semiconductor switching element abruptly changes from the blocking state to the conducting state on application of a predetermined breakdown voltage.
According to the invention, the ignition system has a double ignition coil comprising a primary coil and a secondary coil, the secondary coil having a higher voltage end and a lower voltage end, an ignition line connected electrically to the higher voltage end of the secondary coil and another ignition line connected electrically to the lower voltage end of the secondary coil, said ignition lines containing the semiconductor switching elements and having different lengths, wherein the semiconductor switching element in the one line has a different breakdown voltage than that of the semiconductor switching element in the other line.
Advantageously the semiconductor switching element with the higher breakdown voltage is assigned to the shorter ignition line. The semiconductor switching element can have a plurality of breakdown diodes connected to form a breakdown diode cascade.
The solution, according to the invention, has the advantage that with the use of breakdown or state-changing diode cascades in ignition systems with double ignition coils the high-voltage switch is dimensioned in such a way with respect to its breakdown voltage that the effect of the capacitance of the ignition lines prior to the high-voltage switches is used in such a way that a breakdown diode with a higher breakdown voltage can be arranged in the shorter ignition line. The steepening effect at the corresponding spark plug is accordingly increased relative to the high-voltage switches with the same breakdown voltage. The breakdown voltage of the two semiconductor switching elements is approximately between 11 kV and 20 kV.
When five-layer elements of symmetrical construction which change state in both voltage directions are used as individual breakdown diodes in a cascade, the polarity of the high-v
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patent: 5044348 (1991-09-01), Ookawa
patent: 5044349 (1991-09-01), Benedikt et al.
Herden Werner
Vogel Manfred
Nelli Raymond A.
Robert & Bosch GmbH
Striker Michael J.
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