Actuator and driving method thereof

Abstract

An actuator includes at least two piezoelectric devices arranged for crossing displacing directions thereof at a predetermined angle, a chip member provided at a coupling point of the piezoelectric devices, and a spring for contacting the chip member to a rotor driven by the actuator. The piezoelectric device is driven for moving the chip member trailing an elliptical trail. The rotation velocity or the driving torque of the rotor is controlled by varying at least one of a length of a major axis or a minor axis of the elliptical trail and an inclination angle of the major axis or the minor axis with respect to a normal at a contacting point of the chip member and the rotor.

Description

[0001] This application is based on patent applications 2000-012568 and 2000-097091 filed in Japan, the contents of which are hereby incorporated by references.[0002] 1. Field of the Invention[0003] The present invention relates to an actuator and a driving method thereof for moving a driven object such as a rotor or a rod by intermittently contacting a driving member to the driven object, in which the driving member is moved for trailing a circular or an elliptical trail by utilizing vibrations of at least one of a plurality of displacing elements such as piezoelectric devices.[0004] 2. Description of the Related Art[0005] In recent years, a truss-type actuator is proposed for rotating or moving a driven object in a predetermined direction. In the truss-type actuator, two displacing elements such as piezoelectric devices are arranged to cross the displacing directions thereof at a predetermined angle such as 90 degrees. The displacing elements are respectively driven by alternating...

AI Technical Summary

Benefits of technology

[0010] A purpose of the present invention is to provide an actuator and a driving method thereof in which the moving velocity and the torque of the driven object can be controlled to be desired values even though the electric power consumption of the actuator is substantially constant.

[0012] By such a configuration, a velocity or a torque of the driven object can be varied corresponding to the shape of the elliptical trail of the coupled top ends of the displacing elements. More concretely, a diameter of the elliptical trail in the tangential direction at the contacting point of the coupled top ends of the displacing elements and the driven object influences to the velocity of the driven object, and a diameter of the elliptical trail in the normal direction influences to the torque or driving force of the driven object. Thus, it is possible to make the velocity of the driven object faster by enlarging the diameter of the elliptical trail in the tangential direction, and to make the torque of the driven object stronger by enlarging the diameter of the elliptical train in the normal direction, and vice versa.

Problems solved by technology

The first conventional actuator, however, has a disadvantage that a variation of an electric power consumption is larger and a burden of an electric power supply becomes larger, since the moving velocity of the driven object is controlled by varying the voltage or the frequency of the driving signals.

The second conventional actuator, however, has a disadvantage that the moving velocity varies corresponding to variation of a load of the actuator, since the phase difference of the driving signals is fixed.

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