Process and apparatus for controlling engine operation near the

Abstract

The fuel supply control pulses of an internal combustion engine may be shortened or lengthened to provide operation of the engine at a definite fuel-air ratio. When operation takes place in a leaned-out region, the engine suffers dynamic instability, resulting in rapid fluctuations of the rotational crankshaft velocity, superimposed on regular, periodic changes due to compression changes. The maximum and minimum crankshaft speeds are measured at two different locations of the angular path by passing markers in front of an inductive transducer. The output signals from this transducer are fed to a gating circuit which controls the counting modes of a digital counter which is also supplied with a clocking pulse train at a constant, high frequency. The gating circuit causes alternate upward and downward counting in the counter so that a net difference of counted pulses is formed after each two successive counting periods. This difference is stored until a particular piston of the engine has returned to the functional position it occupied during the first measurement. The measurement is repeated and the difference between the two measurements is compared. The result of this comparison forms a measure of engine roughness and is used for fuel control.