Vibration monitoring device, turbocharger, and vibration monitoring method

A vibration monitoring method, comprising:

• a step of outputting a rotation signal synchronized with rotation of a rotational shaft;
• a step of outputting a filter command value that changes in accordance with changes in corresponding to a rotation speed of the rotational shaft calculated from the rotation signal;
• and
• a step of extracting, in response to input of the rotation signal and the filter command value, a signal in a passband set according to the filter command value from the rotation signal as a vibration signal from which vibration information of the rotational shaft can be obtained.

A vibration monitoring device, comprising:

• a rotation sensor for outputting a rotation signal synchronized with rotation of a rotational shaft;
• an output device for outputting a filter command value corresponding to a rotation speed of the rotational
• shaft calculated from the rotation signal;
• and
• at least one filter for extracting, in response to input of the rotation signal and the filter command value, a signal in a passband set according to the filter command value from the rotation signal as a vibration signal from which vibration information of the rotational shaft can be obtained,
• wherein the filter command value is a current value or a voltage value obtained by converting the rotation speed of the rotational shaft calculated from the rotation signal.