| 摘要 |
PURPOSE:To prevent such condition that the knocking can not be suppressed because of a measurement error, by limiting the correcting amount of lagging angle by means of an average value of the maximum amount of lagging angle if there is a possibility that the ignition timing may be controlled to the lead angle side. CONSTITUTION:A control circuit 20 operates the maximum amount of lagging angle corresponding to a current engine rotary speed based on a pulse fed from a rotary angle sensor 18 with reference to a table stored in ROM. If the maximum amount of lagging angle being operated previous time is larger than a current maximum amount of lagging angle, a weighted average value of them is operated. Consequently, when the maximum amount of lagging angle decreases with increasing engine rotary speed, the ignition timing is lagged by a crank angle corresponding to the weighted average value of previous and current maximum amount of lagging angle. Since the weighted average value varies slowly even when the maximum amount of lagging angle is decreased abruptly by an erroneous measurement of engine rotary speed, abrupt variation of the maximum amount of lagging angle can be prevented. |
