Ignition timing control system for internal combustion engine

Claim 1

An ignition timing control system for an internal combustion engine of the type comprising switching means for interrupting the power supply to an ignition coil in response to an ignition signal, ignition signal generating means for generating said ignition signal in synchronism with the revolution of said engine, an acceleration sensor for detecting the vibratory acceleration of said engine, and control means for controlling the timing of said switching means by said ignition signal in accordance with engine knocking as determined by said acceleration sensor, wherein the improvement comprises: malfunction detection means for generating a malfunction detection signal in response to detection of a malfunction in said ignition timing control system, said malfunction detection means including gate means for receiving said sensor output and for cyclically blocking the passage of said sensor output within the malfunction detection means for at least one predetermined time interval in synchronism with operation of said switching means responsive to said ignition signals; and means in said control means responsive to said malfunction detection signal for controlling the timing of said switching means independently of the presence or absence of engine knocking, wherein said switching means supplies power to said ignition coil during intervals each beginning with a starting time and terminating with a blocking time, and said gate means blocks said sensor output in response to gate control signals, said malfunction detection means further comprising gate control means for generating said gate control signals only at one or both of said starting times or blocking times.