Fuel system for engines and electronic pump circuit, in particular, for a fuel system

摘要

1429771 Automatic control of speed CAV Ltd 21 March 1973 [4 April 1972(2)] 15339/72 and 15341/72 Heading G3R [Also in Division H3] In a system for controlling the fuel supply of an I.C. engine, the speed of the engine is detected by an A.C. tachometer whose output is converted to a D.C. voltage proportional to the frequency of the A.C. signal by means of a diode pump circuit including a capacitor connected across the input and output terminals of an operational amplifier. The control systems described are similar to those disclosed in Specifications 1416861 and 1416862. The A.C. signal is passed through a shaping circuit, Fig. 8 (not shown) to produce a squarewave between terminal 46 and line 23. The voltage developed across the capacitor 96 is proportional to the frequency of the input signal at terminal 46 by reason of its connection across the input and output terminals of operational amplifier 95. The resistor 98 provides a bias so that the zero frequency voltage is high. In a further construction both the pulse shaping and diode pump circuits are modified so that both positive and negative half cycles of the input waveform can be used, Figs. 8 and 11 (not shown). In a modification of the diode pump circuit, Fig. 12 (not shown) an exponentially rising and linearly falling output waveform is obtained, Fig. 15 (not shown) with the maximum and minimum engine speeds forming the end points of the linear portion so that under fault conditions a low output is provided and the circuit thus fails safe.