Engine Simulator to Calibrate RPM and Cam-Dwell Test Sets

摘要

A plurality of dividers, inverters and switching circuits provide for the generation of 33% or 66% cam-dwell angles and the simulation of 4, 6 or 8 cylinders with either a 2 or a 4 cycle engine. Switches are also provided for simulation of the RPM's. In designing the engine simulator, it was desired to have RPM outputs that would be sufficient to check RPM meters at low-, middle-, and full-scale of ranges. These RPM speeds established, to some extent, the numbers of dividers and the master clock frequency. Since the single cylinder RPM output to the HV spark circuit must be correct for given RPM, regardless of the number of cylinders (4, 6, or 8 and 2 or 4 cycle), switching of dividers in and out in certain combinations was required. The cam-dwell function is basically derived from a divide by two or three circuits that in all cases give the correct distributor RPM output for the selected engine. This also required switching of the divider circuits for different cylinder number engines. The divide by three normal or inverted output gives 33% or 66% cam-dwell angles, and the divide by two gives 50% of cam-dwell angles. These three outputs provide all necessary ranges of cam-dwell for selected engine types. Since the frequency of the master clock is much higher and crystal controlled, the low-operating frequencies of RPM outputs are very accurate and the accuracy of cam-dwell, determined by bi-stable circuits, far exceeds any mechanical device being checked.