Ignition system for internal combustion engines
AssigneeRobert Bosch GmbH
InventorWerner Harter
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Abstract
Timing increment signals produced by an engine driven tachogenerator are used for controlling both ignition timing shift and the dwell time of the interruptor switch of the ignition system. Counting of increment pulses by the ignition coil primary current rises to a predetermined value (Io) are measures a dwell time fraction and provides a count result that goes into a computation of which the result measures the duration of a counting of increments between the end of one dwell time and the beginning of the next. For better dynamic behavior the count value representing the dwell time fraction (.beta.t) is corrected in a calculating stage (16-18) by a factor which represents the proportional change in the duration of an increment signal (such a signal at a fixed point in the cycle to the most increment signal).
Claims11
An ignition system for an internal combustion engine including an ignition coil having primary and secondary windings, ignition timing shift means for determining the ignition moment of each cycle of the system, an interruptor switch in circuit with said primary winding electrically controllable so as to provide timing of ignition in response to said ignition shift means by primary circuit interruption and also controllable in circuit closure to provide dwell time for ignition coil energization, said system further comprising;
- a generator of engine rotation increment signals including a rotary device driven by said engine;
- means for counting the number of said increment signals during the initial fraction (.beta.t) of dwell time in which the current in said primary winding builds up to a predetermined value (Io) and for storing said number;
- means (16, 17) for deriving from said number a larger number of increment signals determining a first approximation of the full dwell time;
- means (18) for correcting the output of said number deriving means by the ratio of the duration of the increment signal from said generator appearing at a predetermined point of the cycle of operation of the system to the duration of the most recent increment signal from said generator, and
- means responsive to the corrected derived number provided by said deriving and correcting means to determine the beginning of dwell time.
Dependencies are inferred from the claim text.