Vibration monitoring device, supercharger, and vibration monitoring method

A vibration monitoring device comprising:

• a rotation sensor that outputs a rotation signal synchronized with a rotation of a rotating shaft;
• a detection unit that detects a timing at which a pulse of the rotation signal is generated;
• and
• a vibration waveform restoration unit that restores one waveform of the rotation signal immediately preceding the timing detected by the detection unit as a vibration waveform of the rotating shaft by replacing a first half portion of the one waveform including the immediately preceding pulse of the rotation signal with a reverse phase of a second half portion of the one waveform.

A vibration monitoring method comprising:

• a step of outputting a rotation signal synchronized with a rotation of a rotating shaft;
• a step of generating a cut rotation signal by replacing a portion of the rotation signal equal to or greater than a limit value set in advance with the limit value and by causing a portion of the rotation signal less than the limit value to remain as the rotation signal, when the rotation signal is output;
• a step of generating an offset rotation signal by offsetting the cut rotation signal to approach the limit value;
• and
• a step of extracting a signal in a passband set based on a rotation speed of the rotating shaft from the offset rotation signal as a vibration signal from which vibration information of the rotating shaft is acquirable.