Knock detecting apparatus for internal combustion engines

摘要

A vibrator having a resonant frequency within a knocking frequency range forms a part of a magnetic path. The vibrator vibrates in response to the vibration of an internal combustion engine and this changes the reluctance of the magnetic path. The change in the reluctance is sensed by a coil to detect the presence of knock. The vibrator is enclosed with a damper substance consisting of a liquid or sol substance having viscosity of flow properties so that the vibration of the vibrator is restricted and the Q of the resonance characteristic of the vibrator is deteriorated, thus increasing the substantial range of frequency detection of the apparatus. If necessary, the damper substance is heated to maintain its viscosity at a predetermined value.