GB1301636A - - Google Patents

Abstract

1301636 Fuel injection systems ROBERT BOSCH GmbH 4 Nov 1971 [5 Nov 1970] 51227/71 Heading G1N In an I.C. engine intermittant fuel injection system, injection operations are triggered in synchronism with the rotation of the engine crankshaft by the contact breaker of the engine ignition system via a frequency divider 40, a switching device 32 being provided and including a storage device which is charged, at each trigger operation, to a value dependent upon at least one engine operating variable, the discharge time of the storage device determining, in part at least, the injection quantity delivered by at least one solenoid injection valve, energized from the output of the switching device. As shown, the contact breaker includes a fourlobed cam 35, coupled to the camshaft 17, and contacts 36, 38 connected to the ignition coil 39. Each pulse produced during contact opening is supplied to the frequency divider 40 via a pulse shaper 41 which includes a monostable multivibrator and which prevents faulty triggering, Fig.2 (not shown). The frequency divider 40 includes a bi-stable multi-vibrator, Fig.2 (not shown), which provides a triggering signal, at its output, to the switching device 33 at alternate triggerings from the contact breaker, and therefore once during each revolution of the crankshaft. The switching device 32, Fig.2, (not shown) includes a mono-stable multi-vibrator and a capacitor which, each time a triggering signal is received from the frequency divider, is charged by a constant current dependent upon the quantity of intake air provided during each half revolution of the crankshaft and determined by a potentiometer 29 whose wiper 31 is connected to a baffle plate 30 arranged in the intake manifold 25. The capacitor is then discharged with a constant current and the time taken for discharging determines the duration Tp of the output pulses S provided by switching device 32. The pulses S are preferably applied to a multiplication stage 33 where they are prolonged by a factor f dependent upon operating temperature, position of the butterfly valve, battery voltage and, if required individual operations such as starting. Pulse duration limiting means are provided in stage 41, a signal being applied to the output of device 32 via transistor 92 after the maximum permissible duration.