GB1233639A

GB1233639A -

Info

Publication number: GB1233639A
Authority: GB
Priority date: 1968-09-21
Filing date: 1969-09-19
Publication date: 1971-05-26
Also published as: FR2018587A1; SE341888B; JPS4940890B1; DE1776103B2; AT291682B; DE1776103A1; US3570460A

Abstract

1,233,639. Fuel injection systems. ROBERT BOSCH G.m.b.H. Sept. 19, 1969 [Sept. 21, 1968], No. 46258/69. Heading G1N. [Also in Division H3] In an I. C. engine fuel injection control system, fuel supply to the engine is cut-off when the butterfly valve is in its idling position and the engine speed is a predetermined amount in excess of the idling speed, i.e. when the engine is being driven by the vehicle, fuel supply being restored when the engine speed decreases to a predetermined speed below the cut-off speed but above the idling speed. Opening pulses are supplied to the valves 4 by a monostable multi-vibrator 40 triggered on synchronism with the engine speed by switches 31, 32 in a bi-stable multi-vibrator 20. The pulses from the output transistor 42 of the monostable multi-vibrator 40 are applied to block a transistor 60 which in turn renders a transistor 67 conductive, the transistor 67 being connected to respective AND transisters 16, 17 for respective groups of valves 4. The AND transistors are also connected to the outputs of the bi-stable multivibrator 20. In between opening pulses, i.e. when transistor 42 is blocked, capacitors 73, 76 arranged in a network 71, are charged, the charging voltage of 73, which is effected with short time constant, being dependent upon the temperature of the engine as sensed by N. T. C. resistor 93 but independent of engine speed, the charging voltage of 76, which is effected with long time constant, being dependent upon the engine speed. When transister 42 becomes conductive to produce an opening pulse, capacitors 73, 76 are discharged. When the butterfly valve is in its idling position, a switch S is closed, and if the engine speed is low, the charge stored in a capacitor 90 (which is charged between pulses when transistors 42, 70 are non-conductive) is discharged to apply a blocking pulse to transistor 60, the opening pulse then being applied to a group of valves 4 and transistor 70 being rendered conductive by feedback resistor 86. However, if the engine speed is so high that a negative potential appears at P at the commencement of the next following opening pulse as a result of the incomplete discharge of capacitor 73, transistor 70 can only become conductive during the discharge time of capacitor 90 and then transistor 60 is blocked only during this time which is insufficient to cause opening of the valves 4. Thus when the engine speed reaches a speed no, which is higher for laver temperatures, the fuel supply to the engine is blocked. The supply is unblocked when the engine speed is reduced to a speed n, which is also dependent upon the engine temperature. In an alternative arrangement, Fig.3 (not shown), two such networks 71 are connected in parallel to operate in the transistor 70, the one being temperature dependent as shown in Fig. 1, the other being independent of temperature. When the engine speed increases when the switch S is closed, the fuel supply is cut off by the network which is set to the lower cut-off speed, and the fuel supply is also restored by the network which is set to the lower restoring speed.