GB1449491A - Fuel injection systems - Google Patents

Abstract

1449491 Electronic fuel injection systems for IC engines ROBERT BOSCH GmbH 31 Aug 1973 [1 Sept 1972] 40992/73 Addition to 1330363 Heading G3N In an I.C. engine electronic fuel injection system as claimed in British Patent Specification 1330363 the air quantity meter 26 is coupled to a variable resistor 27 which provides a control voltage which determines the charging and/or discharging operation of the energy storage device, i.e. an inductor or capacitor, in the switching device 30 which is triggered in synchronism with engine rotation to provide the injection valve opening pulses the control voltage being also fed to a differentiating circuit on whose output appears an acceleration-dependent voltage which is used to determine an extra injection quantity for acceleration enrichment. As shown, the air quantity meter is provided by a baffle flap 26 co-operating with a potentiometer 27, the switching circuit 30, Fig. 2 (not shown) including a capacitor which is charged, in synchronism with pulses LJ from an engine triggered signal generator 17, in dependence upon the voltage output of the meter, and is subsequently discharged to produce pulses, Jo. These pulses are applied to a multiplier stage 40, which is similar to the switching stage 30 and provides increased length pulses Js to an OR gate 50 and to a switching device 61. The device 61 is triggered by the trailing edges of pulses Js to provide prolongation pulses Jr to the OR gate 50. The duration of the pulses Jr is determined by acceleration dependent voltage UH at the output of a differentiator P which receives the voltage output UL of the air quantity meter. The resistor 63 may be made dependent upon the temperature of the engine cooling water or oil so that the prolongation pulse Jr is produced only during the warm-up phase of the engine. The OR gate 50 thus provides pulses Js prolonged by pulses Jr to a power stage 20 for energizing the injectors 11. An additional differentiator 64 may be provided whereby additional injection pulses can be triggered in intervals between the pulses Js. In an alternative arrangement, Figs. 4 and 5 (not shown), the voltage UL is applied via a differentiator to one input of a bi-stable trigger which is triggered when the voltage U L increases. The other input of the bi-stable trigger is connected to a threshold switching device whose threshold level is made a function of U L and which is compared with a voltage derived from UL by means of a delay circuit. The threshold device determines the instant of return of the bi-stable trigger to its other state and the output of this trigger is applied to OR gate 50. In a further alternative arrangement, Fig. 6 (not shown), the voltage UH is applied to a switch which controls the damping of a low-pass filter or its limiting frequency. The voltage U L is applied to a monostable trigger device via this low-pass filter.