Internal-combustion engines – High tension ignition system – Electronic cylinder sequencing
Patent
1995-05-22
1996-07-23
Wolfe, Willis R.
Internal-combustion engines
High tension ignition system
Electronic cylinder sequencing
327514, F02P 7073, H03K 1710, H03K 1774, H03K 1778
Patent
active
055379842
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
The present invention relates to a high voltage switch, particularly to a high voltage switch for use in ignition systems of internal combustion engines.
BACKGROUND INFORMATION
German Published Patent Application No. 40 32 131 (the "'131 reference") describes a high voltage switch which assumes the function of an ignition voltage distributor with quiescent high voltage distribution. This high voltage switch consists of semiconductor elements which have light-sensitive zones, and the light-sensitive zones being so actuated by light-emitting elements that they connect through at a prescribed time, e.g., in accordance with the firing order. The individual semiconductor elements in the device of the '131 reference are break-over diodes which are arranged in a cascade circuit. These break-over diodes provide the advantage that when the break-over voltage is reached the high voltage which is built up on the secondary side is suddenly connected through to the spark plugs, so that a voltage loss caused by possible shunt connections, for example due to carbon fouling, is avoided. With the device of the '131 reference, it is not necessary to irradiate the entire cascade circuit with optical energy. It is sufficient to irradiate only part of the break-over diode cascade so that only some of the break-over diodes are switched by means of light and the remaining break-over diodes are connected through when the prescribed voltage is reached and as a result a desired gradient steepening effect is achieved.
SUMMARY OF THE INVENTION
The present invention provides a high voltage switch which has the advantage that the first illuminated sub-stack of break-over diodes has a break-over voltage with a low temperature coefficient. However, at the same time these break-over diodes have break-over currents with a high temperature coefficient. They are thus particularly suitable for the illuminated part since they do not act here as a break-over diode but rather as a light-triggered switch. As a result of the arrangement of the unilluminated part of the high voltage switch, the gradient steepening effect is maintained. This arises from the overhead ignition of the illuminated part of the high voltage switch.
It is particularly advantageous that break-over diodes with low break-over currents with tight tolerances are obtained for the unilluminated second sub-stack of the break-over diode cascade since, in this way, the operation of the break-over diode is maintained for the gradient steepening effect. The combination of these two types of break-over diodes has the advantage that a low temperature coefficient of the switch is obtained and thus the number of semiconductor elements can be reduced. Finally, it is advantageous that the two sub-stacks of the high voltage switch can also consist of two discrete, separately packed components. All that has to be ensured here is that the connecting length between these cascade components be as short as possible.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a schematic representation of an ignition system with a high voltage switch, in accordance with the present invention, having two sub-stacks packed together.
FIG. 2 is a schematic representation of an ignition system with a high voltage switch, in accordance with the present invention, having two separately packed cascade components.
DETAILED DESCRIPTION
FIG. 1 is a diagrammatic view of an internal combustion engine with an ignition system and quiescent high voltage distribution, only two ignition coils being illustrated but a multitude of further ignition coils being possible. A battery voltage U.sub.B is connected to a primary winding 10 of an ignition coil 11, a switching transistor 12 being connected in series with the primary winding 10. The switching transistor 12 is continuously actuated by a control device 13 via its base terminal in order to produce a secondary-side high voltage to the ignition coil 11. A secondary winding 14 of the ignition coil 11 is connected on the one hand to ground and, on t
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Herden Werner
Konrad Johann
Vogel Manfred
Robert & Bosch GmbH
Wolfe Willis R.
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