Piezoelectric detection of IC engine knock vibrations - using single element centrally clamped to provide two independent vibrators

摘要

The sensor for detection of the vibrations occurring as a result of engine knock contains a piezoelectric element and clamp giving a wider bandwidth than conventional arrangements yet suffers no reduction in the magnitude of its resonant peak. This ensures maintainance of the signal-to-noise ratio at a conventional level. The piezoelectric element (1) is clamped so that at least two sections of it are able to vibrate. The clamp (2) may act in the middle of the element so as to produce two equal length vibrating parts (3,4). Selective detection of two frequencies is possible using only a single mechanical clamp. This results in a reduced number of transducers and parts. The transducer signals can be connected in parallel using common electrodes.