GB1398250A - Electrically controlled fuel injection systems for diesel engines - Google Patents

Abstract

1398250 Automatic fuel injection control ROBERT BOSCH GmbH 2 Oct 1973 [3 Oct 1972] 45886/73 Heading G3N In a fuel injection system for a diesel engine 10, Fig.1, wherein solenoid controlled valves 11 are sequentially energized via a distributor 17, the valve opening pulse Jv from a power transistor 18 is controlled in accordance with the rotary speed of the engine, measured in a unit 30, which determines the injection angle, and the pressure in the inlet manifold 24, measured in a unit 20, which determines the injection duration. The control unit 20 consists of a monostable multi-vibrator whose input transistor 21 is blocked by a step voltage 31 to allow transistor 22, 18 to conduct. The collector current of transistor 22 whilst it is increasing, produces a feedback voltage in winding 33 of transformer 23 dependent on the transformer mutual inductance which is controlled by the inlet manifold pressure, and determines the duration of the output pulse J V . The pulse duration may additionally depend on the temperature of e.g. the cooling water and/or the engine speed. The unit 30 is operated by pulses derived by cam switches S1, S2 driven in synchronism with the engine. The cam switch S 1 produces a pulse, in advance from cam switch S 2 by a pre-set angle α, which after differentiation at 44, Fig.3, triggers a monostable multi-vibrator 43 with a period of T 1 . At the end of this period the trailing edge of the output current, after differentiation at 46, triggers a bi-stable multi-vibrator 47 to block a transistor 48 and charge a capacitor 50 through a constant current device 49. The pulse from cam switch S 2 following after an angular delay α, is differentiated at 54 to reset the bi-stable multi-vibrator 47. Hence transistor 48 is opened, and capacitor 50 discharges through constant current device 52, whilst transistor 51 is blocked. When capacitor 50 is discharged, transistor 51 reopens to produce the step voltage 31 for unit 20. This cycle is repeated as the cam switches rotate with the engine. Since the periodic time T of monostable multi-vibrator 43 is fixed and the time between operation of cam switches S 1 , S 2 depends on the engine speed, the timing of the step voltage 31, and hence the beginning of the injection pulse Jv, is also varied with engine speed. The timing device represented by the capacitor 50 and its charge and discharge circuits may be replaced by a reversible counter 70, Fig.4, counting up speed information pulses JD from transducer 80, 81 when the trailing edge of the pulse from monostable multivibrator 43 occurs and counting down when the bi-stable multi-vibrator 47 is reset. At the end of the countdown the step voltage 31 is produced.