GB1262249A - Improvements in fuel injection systems - Google Patents

Abstract

1,262,249. Transistor blocking oscillators and waveform generators. ROBERT BOSCH G.m.b.H. 3 Sept., 1970 [4 Sept., 1969], No. 42107/70. Heading H3T. [Also in Division G1] In an I.C. engine fuel injection control system the relaxation period of a monostable multivibrator 12, which determines injection duration, is determined by the intake manifold pressure, via transformer 15, and in dependence upon engine speed by a control voltage, Fig. 2, which is triggered at the end of each injection pulse produced by the multivibrator 12. As shown, at the end of each injection pulse, i.e. t = 0 in Fig. 2, a capacitor C 4 , which provides the voltage Us applied to point H of multivibrator 12, is discharged, and is then successively charged at instants t 1 , t 2 and t 3 via respective charging sources R 8 , D 2 ; T 3 , R 11 R 13 , D 4 ; and T 4 , R 16 , R 18 , D 7 . The value of the voltage Us attained by C 4 at the end of the next injection pulse (which cause C 4 to be discharged at t=t 4 ) then determines the duration of the succeeding injection pulse. Thus as the engine speeds up, the frequency of injection pulses increases and so the value attained by the voltage on C 4 at the end of each injection pulse varies along the curve of Fig. 2 and so varies injection duration. In a modification, Fig. 3 (not shown), a second storage capacitor C 5 is provided in parallel with the capacitor C 4 in such a manner that the control voltage Us, Fig. 4 (not shown), is determined by the capacitor having the more positive voltage at any instant. In an alternative embodiment, Fig. 5 (not shown), a single storage capacitor C 6 , after being discharged at the end of each injection pulse, is charged by a first charging source, discharged, and then charged once or a successive number of times by a second or a successive number of different charging sources, to provide a control voltage Us, Fig. 6 (not shown), which increases and decreases.