Patent ID: 8855816

Claim:
A piezoelectric actuator comprising: a vibrating body that includes a piezoelectric device; a driving unit that supplies a driving signal to the piezoelectric device; a phase difference detector that detects a phase difference between the driving signal and a detection signal detected based on vibration of the vibrating body; and a control unit that controls the frequency and power of the driving signal, wherein when the frequency of the driving signal is changed so that the phase difference falls within a predetermined range, the control unit stores the value of the frequency as a first frequency memory value, sets the power of the driving signal to a predetermined value, and performs control of adjusting the frequency of the driving signal so that the phase difference is maintained to be within the predetermined range, and when the frequency of the driving signal is changed from the first frequency memory value by an amount exceeding a first value determined in advance based on temperature characteristics of a resonance frequency of the vibrating body, the control unit sets the power of the driving signal to a value smaller than the predetermined value.