GB1448567A - Fuel injection systems - Google Patents

Abstract

1448567 Regulating IC engine fuel injection PHYSICS INTERNATIONAL CO 28 Nov 1973 55215/73 Heading F1B [Also in Division G3] In a fuel injection system for a diesel or gasolene engine, the pressure in a common fuel feed line is varied in accordance with an "n" th power, established by engine tuning, of either the engine speed, or the air mass flow to it. Thus the rate of fuel injection can be controlled. As shown diesel engine fuel is circulated in feed line 14 by feedpump 12, the flow, and hence feed line pressure being controlled by pressure control valve and actuator 24, 26. Device 32 provides pulses of frequency determined by engine speed to tacho 40 whose output voltage representing engine speed is raised to the "n" th power in log-multiply-antilog circuit 42 and compared with a signal from transducer 30 representing actual fuel rail pressure in voltage comparator (44), Fig. 4 (not shown), to enable switch (102) only if the actual pressure signal from the transducer 30 is less than the calculated signal, whence voltage controlled oscillator (100) providing an output pulse frequency proportional to the difference signal from subtractor (98), can, via driver (46) operate actuator 26 to increase the rail pressure until the latter exceeds the calculated value, whence pressure increase ceases. Pulses from device 32 are shaped in unit 34, and disstributed to electrically operated injector valves 16, 18, 20, 22, the duration of their opening being dependent upon signals from operator control 36, and from unit 38 allowing the duration to change in dependence on engine speed, fuel rail pressure, load, smoke level or air consumption. "n" may be greater than, or less than 1, e.g. 2. Gasolene engine, Figs. 5, 6 (not shown) transducer (111), (Fig. 6) measures the pressure in fuel rail (114A, 114B) with respect to the inlet manifold (128), the calculated value with which the transducer output is compared representing a power of the air mass flow, calculated as a function of pressures (P 1 ,P 2 ), (Fig. 5) in a Venturi (106), and the ambient temperature, in calculator (109), see also Fig. 7 (not shown) and in log-multiply-antilog circuit (42). Rail pressure is controlled as for the diesel engine, but is constrained to be above a certain valve to avoid vaporization. The pressure may be determined in dependence on engine speed. Pressure control by pressure control valve 24 and actuator 26. Fuel flow from rail 14 to bowl 10 is resisted by a spring-biased valve-member (68), Fig. 3 (not shown) in the pressure control valve. The actuator 26, which is a pump, Fig. 2 (not shown) having Piezo-electric, magnetostrictive, or solenoid drive of a piston (54), which may be alternatively driven by an eccentric, provides an incremental pressure with respect to that in line 14, in relation to its actuation rate, to chamber (76), (Fig. 3) providing a further bias to valve (68) and hence increasing rail pressure as long as actuator 26 is operative. When actuator 26 ceases to operate, leakage around and through pierced plug (78), (Fig. 3) enables the rail pressure to decrease until actuator 26 operates again. Pierced diaphragm spring (80) and the pierced plug (87) control hysteresis and hunting in the control characteristic.