Switching control circuit, especially for motor vehicle engines

摘要

The actuation of electromagnetic devices, especially fuel or mixture shut-off solenoid valves in internal combustion engines is controlled on the basis of two engine variables, namely engine speed (rpm) and induction tube vacuum, for the purpose of suppressing fuel or mixture admission to the engine when the engine is being operated at higher than normal idling speed and while the throttle is closed (engine vacuum high). These twin conditions indicate that the engine is used for braking, i.e., it is being overrun. The position of the throttle is sensed by a vacuum switch which responds to induction tube vacuum and releases the actuation of the solenoid valve. The solenoid valve is further engaged by an rpm-dependent circuit in which a capacitor is periodically discharged by rpm related pulses.