| 摘要 |
PURPOSE:To suppress rolling of chassis under engine stop, in an internal-combustion engine for car, by prohibiting spark discharge irrespective of production of firing control signal when the engine rotation is lower than specific level which is lower than the idling rotation. CONSTITUTION:Upon dropping of engine rotation below specific level lower than idling rotation, the time interval between production of positive timing pulse from a pulser coil 11 and production of negative timing pulse is lengthened against the time interval when the collector voltage of transistor Q3 in prohibition circuit 15 is H to bring the transistor Q2 into on-state when producing the negative pulse or at the firing timing thus to prohibit firing function. In other word, at the firing timing when the firing control signal will transfer from H to L, power transistor Q1 is turned off to produce counter electromotive force in an ignition coil 6, but since it is fedback through transistor Q2, Zener diode ZD1 to the base of power transistor Q1, secondary voltage of coil 6 is suppressed thus to never cause discharge from the firing plug 7, resulting in suppression of rolling of chassis under engine stop. |
