Piezo-electric motor intended for a timepiece

Abstract

This motor of the piezo-electric type comprises a stator (1) and a rotor (15) intended to effect relative movement to one another. The stator (1) comprises a plate (17) of generally planar form and means for generating therein vibratory waves at an ultrasonic frequency. Such waves enable the imparting of an elliptic motion to at least one active point (17c) on the periphery of the plate in the plane of the latter, said active point being in engagement with a motion transmission surface (22) of the rotor (15) in order to bring about movement of the rotor (15) relative to the stator (1) by virtue of the elliptic motion. The plate (17) of generally planar form includes a central circular portion (17a), to one of the faces of which are attached the means for generating the vibratory waves. From this central portion extend at least two lobes (17b) on the edges (17d) of which are arranged said active points (17c). The lateral edges (17d, 17e) of lobes (17b) are profiled so as to concentrate the vibratory energy emanating from the central portion (17a) within the active points (17c). Thus one of these edges preferably exhibits an elliptical profile. The invention is applicable to motors intended to furnish a low couple with a high yield, in particular in the horological domain.