GB1445709A - Electrically controlled fuel injection systems for internal combustion engines - Google Patents

Abstract

1445709 Transistor pulse circuits ROBERT BOSCH GmbH 30 Aug 1973 [31 Aug 1972] 40860/73 Heading H3T [Also in Division G3] In/an I.C. engine electronic fuel injection system (see Division G3) injection valves opening pulses are provided, via a power stage, by a monostable multivibrator 23 triggered in synchronism with engine rotation by a switch 30, a pulse-shaper 21 and a frequency divider 22. The multivibrator 23 includes a timing capacitor C which is charged with constant current Ia from a source A, Fig. 4 (not shown), over a fixed angle of crank-shaft rotation. The transistors T1 and T11 are blocked during the charging period whereas the transistors T2 and T12 are conductive, the transistor T4 being maintained in its non-conductive state by way of transistor T3 which is then conductive. This state is ensured by the control of the transistor T3 by means of the switching voltage 80 from divider 22 and thus prevents the charging operation from being terminated prematurely by any voltage surges on line 35. The charging operation is terminated only when voltage 80 jumps to zero. The differentiating capacitor 87 then transmits a negative pulse k to the base of T1 which becomes conductive. The second switching voltage 81 from divider 22 at the same time blocks source A and the charge on capacitor C blocks the transistors T2 and T12 so that transistor T3 becomes non-conductive and T4 conductive. During the discharge of C which then commences, the source E of discharge current, Fig. 5 (not shown), supplies a constant discharge current Ie which causes the voltage Uc across capacitor C to drop linearly. As soon as this voltage has attained zero value, the transistor T2 assumes its conductive state and, despite the zero value of the voltage 80 still prevailing, its collector current flowing through resistor 94 puts transistor T3 into its conductive state. Transistor T3 then renders the feedback loop effective and blocks transistor T4 and at this instant the previously existing control pulse Jo is terminated. The control pulse Jo has a duration proportional to the quantity of air entering the cylinder at each induction stroke, and either the charging current or the discharging current can be made dependent upon this quantity.