BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 shows a timepiece according to a preferred embodiment of the invention.
FIG. 2 is a plan view of the date display device in a preferred embodiment of the invention.
FIG. 3 is an oblique view of the piezoelectric actuator unit in a preferred embodiment of the invention.
FIG. 4 is a plan view of the piezoelectric actuator unit in a preferred embodiment of the invention.
FIG. 5 is a block diagram showing the arrangement of the piezoelectric actuator drive control device in a preferred embodiment of the invention.
FIG. 6A is a graph showing the relationship between drive frequency and impedance and FIG. 6B is a graph showing the relationship between drive frequency and the amplitude of longitudinal vibration and sinusoidal vibration in the vibrator in the preferred embodiment of the invention.
FIG. 7 is a graph showing the drive characteristic when sweeping the drive signal pulse width in a preferred embodiment of the invention.
FIG. 8 is a flow chart of piezoelectric actuator drive control in a preferred embodiment of the invention.
FIG. 9 is a timing chart of piezoelectric actuator drive control in a preferred embodiment of the invention.
FIG. 10 is a graph of power consumption during piezoelectric actuator drive control in a preferred embodiment of the invention.
FIG. 11 is a flow chart of piezoelectric actuator drive control in a first variation of the first embodiment of the invention.
FIG. 12 is a flow chart of piezoelectric actuator drive control in a second variation of the first embodiment of the invention.
FIG. 13 is a block diagram showing the arrangement of the piezoelectric actuator drive control device in a fourth variation of the first embodiment of the invention.
FIG. 14 shows a timepiece according to a second embodiment of the invention.
FIG. 15 is a block diagram showing the arrangement of a piezoelectric actuator drive control device in this embodiment of the invention.
FIG. 16 is a block diagram showing the arrangement of the controller of a piezoelectric actuator drive control device in this embodiment of the invention.
FIG. 17 is a graph showing the change in phase difference, rotor speed, and current when sweeping the drive signal frequency in a vibrator in this embodiment of the invention.
FIG. 18 is a partial enlargement of the graph in FIG. 17.
FIG. 19 shows a data table stored in the storage unit in this embodiment of the invention.
FIG. 20 is a flow chart of the optimum phase difference acquisition step and phase difference inversion detection step of the piezoelectric actuator drive control device in this embodiment of the invention.
FIG. 21 is a flow chart of the drive step of a piezoelectric actuator drive control device in this embodiment of the invention.
FIG. 22 is a flow chart of the low power consumption drive process P6 of the drive control device in this embodiment of the invention.
FIG. 23 shows the change in the piezoelectric actuator drive characteristic in this embodiment of the invention.
FIG. 24 is a graph of the piezoelectric actuator drive characteristic in this embodiment of the invention.
FIG. 25 is a graph of the drive characteristic of the piezoelectric actuator in this embodiment of the invention without drive frequency limiting for comparison with the graph in FIG. 24.
FIG. 26 is a flow chart of piezoelectric actuator drive control in a first variation of the second embodiment of the invention.
FIG. 27 is a flow chart of piezoelectric actuator drive control in a third variation of the second embodiment of the invention.
FIG. 28 is a block diagram showing the arrangement of the drive control device in a third embodiment of the invention.
FIG. 29 is a flow chart of the optimum phase difference acquisition step of the piezoelectric actuator drive control device in this embodiment of the invention.
FIG. 30 is a graph showing change in phase difference, rotor speed (drive), and current when sweeping the drive signal frequency.