GB1369232A - Control systems for road vehicles - Google Patents

Abstract

1369232 Transistor switching circuit JOSEPH LUCAS (INDUSTRIES) Ltd 7 Feb 1972 [17 Feb 1971] 4880/71 Heading H3T [Also in Division G1] In a control system comprising a radiation source and a radiation detector with means drivable by an engine for repeatedly exposing the detector to the radiation, means are operated when the detector is exposed to the source regeneratively to increase the current flow through the source. In an embodiment, Fig. 1, for a vehicle ignition system a light emitting diode 21 is positioned so that it can illuminate a phototransistor 26 via a slotted shutter. A Zener diode 17 provides a constant bias on the base of the transistor 18 so that the current flow through the transistor 18 is just sufficient to energize the diode 21 so that it is radiating light. When the phototransistor 26 is illuminated it will start to conduct and turn on the transistors 22 and 27 which in turn will provide additional current through the diode 21 so that the illumination increases, which in turn increases the conduction of the transistor 26. Conduction of transistors 22 and 27 turns off transistors 29 and 33 causing the flux in the core of the transformer 35 to collapse and a spark to be produced. In an embodiment (Fig. 4, not shown) for limiting the maximum speed of an engine, transistors 29, 33 and the transformer 35 &c. are replaced by a diode pump circuit (frequency to voltage converter) coupled to a switching device which changes state when the engine speed reaches a predetermined value and activates a relay preventing the ignition coil of the engine from operating until the speed drops below the predetermined value. A further embodiment, Fig. 3, for fuel injection is similar to the Fig. 1, embodiment except that the slots in the shutter 42 are chosen such that a slot occurs at the instant at which injection is to start. The transistor 29 activates a further transistor and a fuel injector.