Pressure fluctuation measurement in engine combustion chambers - using sparking plug with electrode chamber tuned to knocking frequency

摘要

Pressure fluctuations in engine combustion chambers are measured by an ion current probe with two electrodes in the combustion gases between which is applied a measurement voltage. A connecting channel between the electrodes joins the combustion chamber and a dead space volume. It reliably detects fluctuations due to knocking over a wide engine operating range. The dead volume (79) is so blind hole reaching from the projecting end (78) of the first electrode, in the form of a central sparking plug electrode (73), into the electrode. The second electrode (77) is the earthed electrode of the plug which is bent over the central electrode to form an ignition spark gap. The blind hole dimensions are selected to promote resonant gas oscillations at the frequency peculiar to knocking.