The present application is based on, and claims priority from JP Application Serial Number 2020-112530, filed Jun. 30, 2020, the disclosure of which is hereby incorporated by reference herein in its entirety.

BACKGROUND

1. Technical Field

The present disclosure relates to a piezoelectric drive device, a piezoelectric motor, and a robot.

2. Related Art

For example, a piezoelectric motor disclosed in JP-A-2015-186329 has a rotor as a driven unit, a vibrator vibrating by expansion and contraction of a piezoelectric element, and a spring urging the vibrator toward the rotor and pressing the vibrator against the rotor.

However, in the piezoelectric motor in JP-A-2015-186329, the spring extends in directions orthogonal to longitudinal vibration directions of the vibrator in a natural state, and tilts relative to the directions orthogonal to the longitudinal vibration directions of the vibrator in an urging state in which the vibrator is urged. Accordingly, it is difficult to accurately control the rotation of the rotor because an amount of movement or a movement velocity of the rotor differs depending on the rotation direction of the rotor, i.e., between a case of the forward rotation and a case of the backward rotation.

SUMMARY

A piezoelectric drive device according to an aspect of the present disclosure includes a vibrator having a vibrating portion including a piezoelectric element and performing longitudinal vibration and flexural vibration, and a convex portion placed in the vibrating portion and performing an elliptic motion, and an urging member including a base, a holding portion holding the vibrator, and a spring portion coupled to the base at one end and coupled to the holding portion at another end and urging the convex portion toward a driven unit, wherein d1>d2 is satisfied in a natural state in which the vibrator is not urged by the urging member, where a separation distance between the one end and the convex portion along directions of the longitudinal vibration is d1 and a separation distance between the other end and the convex portion along the directions of the longitudinal vibration is d2, and |d1−d2| in an urging state in which the vibrator is urged toward the driven unit by the urging member is smaller than |d1−d2| in the natural state.

