PURPOSE: To accurately detect the actual ignition timing, by setting a threshold level for detecting the actual ignition timing to the zero level of an ignition signal serving as a reference and changing the threshold level in accordance with a change of the zero level of the ignition signal.
CONSTITUTION: An ignition detector has a light receiving element 42 such as a phototransistor detecting light of ignition, outputting an ignition timing pulse signal from an ignition timing pulse generator circuit 25 in accordance with an output signal of the light receiving element 42. This ignition timing pulse generator circuit 25 has a load resistor 101, which generates voltage Va corresponding to light of combustion at a point (a), and linear inverting amplifiers (103W106) which amplify this voltage Va to voltage Vb having a suitable level. Further the generator circuit 25 provides a zero detecting threshold setter 25b in which threshold voltage Vc for detecting rise-up timing (ignition timing) of the voltage Vb is correctively set by detecting a zero level of the voltage Vb as a reference level.
YASUURA NOBUSHI
TSUZUKI YOSHIHIKO
KAMEOKA SHIGETOSHI
OOSUGA ISAO
