GB1467551A - Apparatuses for indicating relative compression differences in a multi-cylinder internal combustion engine - Google Patents

Abstract

1467551 Monitoring cylinder pressure in I C engines: monitoring voltage peaks SVENSK BILPROVNING AB 27 Feb 1975 [4 March 1974] 8325/75 Headings G1N and G1U Excessive variation between the cylinder pressures of an I.C. engine are detected by looking for excessive variation in the peaks of the starter motor current whilst the starter motor is turning the, non- firing, engine. As described in a first embodiment the starter motor current which is detected by a Hallplate pick-up 1, 2, Fig. 2, has an initial peak Ap, Fig. 1 which is detected 3, Fig. 2, to set on a monostable 4. The first peak, A1, Fig. 1, after the monostable 4 resets is sampled and held 7, and each subsequent peak, typically peak Ar, is compared with A1 by an arrangement 8, 9, which only produces an output to set a trigger 11 'on' whenever k|A1-Ar|#A1, k being a pre-set constant determined by a feedback resistor 14. The setting on of trigger 11 sets a trigger 12 to provide a visual indication 13 of the existence of excessive pressure differences. The above process continues until a counter 6, which was reset to zero by the output from the monostable 4 and which has subsequently been counting the peaks A1, A2, ... &c., becomes full, whereupon the next peak to occur is sampled and held 7 in place of the peak A1, and the trigger 11, if on, is reset off. The process then continues, as above, but with the peak A 1 replaced by a more recent peak. In a second embodiment Fig. 4 (not shown) each peak, after the initial period td, Fig. 1, to allow transients to die out, is compared with a pre-set fraction of the largest of the peaks that precedes it.