Apparatus for controlling the operating current of electromagnetic devices

摘要

Electronic control circuitry is provided for controlling the actuating current of electromagnetic devices and in particular of the electromagnetic fuel injection valves of an internal combustion engine. In order to program the magnitude of the actuating current from an initial high level to a lower maintenance level, there is provided a driver circuit which receives fuel injection control pulses from a fuel injection system, not itself part of the invention, and processes these control pulses into valve-actuating current pulses. The valve current is sensed by suitable transducer, for example a resistor, and the resulting signal is fed to a two-point controller which suitably alters the input to the driver circuit to thereby change the valve actuating current. The set-point value on which the two-point controller operates is itself subject to change by means of a suitable circuit. There is further provided a free-running circuit and a quenching circuit for reducing the voltage peaks resulting from the collapse of the magnetic fields stored in the valve actuating coils. Two embodiments are presented.