GB1520427A - Process of and system for regulating the operating behavaiour of an internal combustion engine - Google Patents

Abstract

1520427 Determining rough running in IC engine ROBERT BOSCH GmbH 18 July 1975 [19 July 1974 (2)] 30179/75 Addition to 1509075 Heading GIN [Also in Division G3] In an I.C. engine, the fuel/air ratio and/or the amount of exhaust gas fed back is controlled in response to the roughness (cyclic variations in speed) of the engine. The object is to operate with as lean a mixture as possible. In a first embodiment the crank-shaft carries two discs 10, 12, the first rigidly coupled and the second via a torsion spring element 14 of low natural frequency. Thus, the disc 12 rotates substantially smoothly at engine speed and angular differences occur between the discs due to the engine fluctuations which are detected by an inductive device 11, 13, 16. Pulses from this are applied to a logic circuit Figs. 5 and 6 (not shown) by which two capacitors are charged for a time equal to the angular displacement of the discs on two successive cycles respectively, and at a rate dependent on engine speed. The voltage difference between the capacitors is thus a measure of speed fluctuations (roughness) and this is compared with a reference (which may be dependent on speed, induction pipe pressure and/or engine temperature). The combustion mixture is progressively weakened by a ramp voltage produced by an integrater, but if the roughness signal exceeds the reference the integrator is inhibited so that the weakening is halted. In an alternative embodiment, Fig. 8, the signal corresponding to smooth rotation at engine speed is produced electrically. Pulses produced by a signal crank-shaft pick-up 11, 16 are squared and compared in phase at 115 with pulses at a steady frequency from a generator 116. The difference is double integrated at 118, 119 and 120, 121, the resulting voltage corresponding to average engine speed being used to control the frequency of the generator 116. With this arrangement a second output of the comparator 115 occurs only when the engine speed departs from average, and for a time dependent upon this departure. This output controls a switching transistor 134 which allows a capacitor 131 to be charged while the output is present and at a rate determined by the speed dependent voltage via amplifying transistors 123, 124. Thus, the charge on the capacitor corresponds to the momentary angular displacement of the crank- shaft, i.e. the "roughness" of the engine, and is compared with a reference voltage to control the combustion mixture as in the first embodiment.