PURPOSE: To raise the sensitivity by giving a resonance characteristic to a vibrating body which vibrates in accordance with the vibrations of the internal combustion engine, at the frequency of knocking.
CONSTITUTION: The vibrating body 21 made of a magnetic substance which vibrates in accordance with the vibrations of the internal combustion engine 1, an exciting coil 22 as a magnetic-flux generating means for supplying the magnetic flux to a magnetic path containing the vibrating body 21, and a magnet 22A are provided. And, a magnetic-flux detecting means 25 which detects the change of the magnetic flux in the magnetic path based on the vibrations of the vibrating body 21 and generates an electric output corresponding to the vibrations of the body 21 and an output adjusting means 41 for adjusting the output generated in the detecting means 25 are equipped. By giving the resonance characteristic to the vibrating body 21 at the frquency of knocking, the detection of even minute knocking is made possible and thus the sensitivity of the detector can be raised remarkably.
HATSUTORI TADASHI
OOTSUKA YOSHINORI
