GB1261223A - Improvements in or relating to fuel injection systems for internal combustion engines - Google Patents

Abstract

1,261,223. Transistor pulse circuits. ROBERT BOSCH G.m.b.H. 9 May, 1969 [11 May, 1968], No. 23652/69. Heading H3T. [Also in Divisions F1, G1 and H1] In an electronically controlled I.C. engine fuel injection system, during acceleration fuel enrichment is provided by an additional number of opening pulses produced between the normal opening pulses, the additional opening pulses being triggered by a device connected to the butterfly valve in the intake manifold when this butterfly valve is opened during acceleration. The number of additional pulses is dependent upon the amount the butterfly valve is opened. As shown, the normal opening pulses, having a duration dependent upon the intake manifold pressure, are produced by a control multivibrator 150 which is triggered in synchronism with the engine speed by switches 101, 102 via a bi-stable multivibrator 130, these opening pulses being applied to two groups of solenoid injection valves 110, 120 via a device 170, an OR gate 165 and respective AND gates 115, 125 dependent upon which switch 101, 102 is closed, the switches 101, 102 being alternately closed for 180 degrees of the crank-shaft rotation. Additional pulses of constant duration are produced by a monostable multivibrator 250, having a capacitor 257 as its timing element, and are applied to OR gate 165, the multivibrator 250 being triggered by a bi-stable multivibrator 230 which is switched over by a switch 40 operated when the butterfly valve is opened. In an alternative, Fig. 9 (not shown), the device 170 is replaced by a multiplier circuit (300) containing a storage capacitor (305). The multivibrator 150 produces pulses (Js) having a period during which the capacitor (305) is charged by a charging current (i 1 ). As described, the discharge current is selected to be equal to the charging current (i 1 ) and the normal opening pulses (Jn) at the OR gate 165 have a duration which is twice that of pulses (Js). These pulses (Jn) are applied to the solenoids via OR gate 165 and AND gates 115, 125 as above. The additional pulses (Z) are produced as above but in this case they also cause the normal pulse (Jn) to be prolonged. During each additional pulse a capacitor (263), connected in an emitter follower circuit to the output transistor 252 of multivibrator 250, is charged in steps, each step corresponding to an additional pulse. The transistor (265) of the emitter follower circuit supplies a current (i 2 ) to the capacitor (305) thus increasing the charging current of (305) to i 1 + i 2 and thus prolonging the normal pulse (Jn). The capacitor (263) has a large time constant and so each pulse (Jn) is prolonged even after the additional pulses are discontinued. The multivibrator 250 may be provided with means (253), (254) for shortening successive additional pulses. In a further modification, the output of multiplier (300) is connected directly to each AND gate 115, 125, the output of each AND being connected to one input of one or two OR gates, the other input of each OR gate being connected to the output of the multivibrator 250. In the above embodiments, any additional pulses triggered during the period of a normal pulse are lost in that normal pulse. In the embodiment of Fig. 11 (not shown), any additional pulse occurring during a normal pulse is added to the end of that normal pulse. The output of OR gate 165 is connected to a combined multivibrator and logic circuit which is triggered by the bi-stable multivibrators 230. The multivibrator and logic circuit is also connected to a respective AND gate 115, 125, the connections to the OR and AND gates having a common junction (G) in the multivibrator and logic circuit. Each AND gate 115, 125 can only be triggered when the potential at (G) is negative, and this occurs during the normal pulse from multiplier (300) and during the period of any additional pulse when the output transistor (272) of the multivibrator is conductive. The duration of the additional pulses is again determined by the charging time of a capacitor (282) in the multivibrator. If an additional pulse is triggered during a normal pulse the charging of the capacitor (282) is delayed by the logic circuit until the end of the normal pulse and the additional pulse is thus added to the end of the normal pulse.