Patent ID: 8421309
Filing Date: 2013-04-16
Classification: H02N

Abstract:
1. An ultrasonic motor at least comprising: a vibrator having a dimension ratio of a rectangle in a cross-section orthogonal to a central axis; and a rotor that is in contact with an elliptical vibration generating surface of the vibrator and that is rotated around the central axis, which is orthogonal to the elliptical vibration generating surface of the vibrator, wherein an elliptical vibration is generated by combining a longitudinal primary resonance vibration resulting from an expansion and a contraction of the vibrator in a direction of the central axis and a torsional secondary resonance vibration or a torsional tertiary resonance vibration resulting from twisting of the vibrator about the central axis, the dimension ratio of the rectangle of the vibrator is chosen such that a resonance frequency of the longitudinal primary resonance vibration resulting from the expansion and the contraction of the vibrator in the direction of the central axis and a resonance frequency of the torsional secondary resonance vibration or the torsional tertiary resonance vibration resulting from twisting of the vibrator about the central axis substantially match, and the vibrator includes, stacked in a short side direction of the cross-section, at least one torsional piezoelectric body that generates the torsional secondary resonance vibration or the torsional tertiary resonance vibration, and a piezoelectric body for longitudinal vibration that generates at least a longitudinal primary resonance vibration.