GB1337024A - Fuel injection systems - Google Patents

Abstract

1337024 Transistor monostable circuits ROBERT BOSCH GmbH 4 Aug 1971 [5 Aug 1970] 36565/71 Heading H3T [Also in Division G1] In a fuel injection system having a plurality of injection valves and a monostable triggering stage for controlling the opening of the injection valves the monostable stage has cross coupled transistors 26, 28, a timing capacitor 30 and a resistor 33 connected to the base of the input transistor 26 and a control transistor 44 of opposite conductivity type to the other transistors 26, 28 with its emitter-collector path and emitter resistor 45 connected in parallel with the resistor 33 so as to provide additional charging current for the capacitor 30 variable in dependence on the control potential U s applied to transistor 44. In the stable state the input transistor 26 conducts and a negative input pulse 35 causes the transistors 26 and 28 to turn off and on. This state is retained until the capacitor 30 has charged, via 33 and via 44 and 45, sufficiently for the base-emitter voltage U B to exceed the threshold voltage of transistor 26 which turns on and this turns off transistor 28. The four cylinder, four stroke IC engine crank-shaft drives a cam (38, Fig. 1, not shown) which operates to close a contact (39) and discharge a capacitor (40) so as to produce the input pulses 35. The control voltage U s is applied to the monostable circuit of Fig. 2 (20, Fig. 1) from a potentiometer (24) coupled to a throttle pedal (19) so as to vary the unstable period of the monostable circuit and therefore the open period of the fuel injection valves (13) in dependence on the throttle position. The output pulses from the monostable circuit switch a power transistor (18) which operates the solenoid windings of the injection valves (13).