Current flowing time period control system for ignition coil of internal combustion engine

Abstract

A current flowing time period control system for an ignition coil of an internal combustion engine is disclosed in which a current flowing time period setting circuit sets the time period for supplying the primary current of the ignition coil and an output signal of the current flowing time period setting circuit is amplified by a drive circuit and supplied to a power transistor, whereby the primary current of the ignition coil is intermittented to control the ignition operation. The current flowing time period control system has a primary current rise detection circuit for detecting the rise period of the primary current of the ignition coil to 1/n of the desired interruption current value (n>1), and includes an accumulation device in which the accumulated amount changes gradually in one direction at a first rate until detection of the rise of the ignition coil primary current to 1/n of the desired interruption current value by the rise detection circuit, in the other direction at a second rate gradually at an ignition timing, and again in the original direction at a third rate 1/n of the first rate. In accordance with the accumulated amount of the accumulation device, a time length n times longer than the time period required for the rise of the ignition coil primary current to 1/n of the desired interruption current value is set as a primary current flowing time period for the next ignition cycle.

Dependencies are inferred from the claim text.