Physik Instŕumente (pi) Gmbh & Co. Kg

Physic Instrumente (pi) Gmbh & Co., Kg

Alexej Wischnewskij

Wladimir Wischnewskij

Wladimir Wischnewskiy

Reinhard Hübner

Ulrich Brüggemann

Siegfried Lindig

A method for electrically exciting a piezoelectric actuator of an ultrasonic motor is described. The ultrasonic motor has at least one acoustic standing wave generator, including an exciter electrode and a general electrode, wherein a capacitance Cis developed between the exciter electrode and the general electrode. The method includes: applying a rectangular exciter voltage Uto the exciter electrode and the general electrode of the acoustic standing wave generator; providing a voltage Uwith the aid of a feedback element; separating a voltage ufrom a voltage uwith the aid of a pulse filter; and changing the frequency of the rectangular exciter voltage in such a way that the phase shift between the piezoelectric current Iand the rectangular exciter voltage Uis substantially zero. A device for electrically exciting a piezoelectric actuator of an ultrasonic motor is also described.

Method and device for electrically exciting an actuator for an ultrasonic motor

An ultrasonic motor is described. The ultrasonic motor includes a plurality of plate-shaped piezoelectric ultrasonic actuators. Each of the ultrasonic actuators includes at least one friction element allocated thereto. Each ultrasonic actuator or each of one or more pairs of ultrasonic actuators is assigned an element to be driven. The ultrasonic motor also includes a housing. The ultrasonic motor also includes an electric excitation device. The elements to be driven are movable independently of each other, and each ultrasonic actuator or each of the one or more pairs of ultrasonic actuators is arranged in a holder. The holders are pressed against each other by housing side covers. The friction elements on the ultrasonic actuators are pressed against a friction layer of the corresponding element to be driven by an elastic interlayer that is in contact with edge surfaces of the ultrasonic actuators that are arranged opposite the friction elements.

Ultrasonic motor

An exemplary actuator in the form of a plate is disclosed, which includes, at least two generators for exciting an acoustic standing wave in the actuator. The actuator can have at least two main surfaces and a plane of symmetry S running perpendicularly to the main surfaces, with respect to which the generators are arranged symmetrically. A first lateral surface area can have a length L that substantially corresponds to the wavelength of the acoustic standing wave excited in the actuator. A second lateral surface area of the actuator can have a length (B) that is greater than the wavelength of the acoustic standing wave excited in the actuator, and that is not equal to a multiple of half the wavelength of the excited acoustic standing wave.

Actuator

A piezoelectric actuator, especially for an ultrasonic motor, includes an acoustic oscillation resonator, wherein the acoustic oscillation resonator is substantially formed as a rectangular piezoelectric plate with two main surfaces, two side surfaces and two end faces and has a multilayer structure in its interior which represents a layer of excitation electrodes taking turns with the layers of the common electrodes and the layers of polarized ceramic provided therebetween, with the polarization vector extending perpendicularly with respect to the surface of the electrodes, wherein all excitation electrodes are divided into two groups not connected to each other, which are disposed symmetrically with respect to the symmetry surface of the aforementioned plate, wherein this symmetry surface extends perpendicularly with respect to the main and side surfaces of the plate, namely through the center thereof.

Piezoelectric actuator for an ultrasonic motor

The invention relates to an ultrasonic actuator, preferably for use in an ultrasonic motor, in the form of a piezoelectric plate with a length L, height H and thickness t, wherein the piezoelectric plate has a lateral plane of symmetry Sq, a longitudinal plane of symmetry Sl and at least two main surfaces, and the piezoelectric plate comprises at least two generators symmetrically disposed with respect to plane of symmetry Sq for generating ultrasonic standing waves. According to the invention, the piezoelectric plate has a shape that includes at least eight lateral surfaces, wherein at least two of the lateral surfaces are working surfaces for contacting of elements to be driven, and at least two of the lateral surfaces are holding surfaces for holding the piezoelectric plate, and the remaining lateral surfaces are free surfaces, wherein at least four free surfaces are arranged at an identical angle &#x3b1; with respect to the longitudinal plane of symmetry Sl and/or at an identical angle &#x3c6; with respect to the lateral plane of symmetry Sq.

Ultrasonic actuator

The invention relates to an ultrasonic linear drive unit comprising a driving element as an ultrasonic oscillator with two generators for ultrasonic vibrations and a driven element that forms a frictional contact with the driving element, and an electrical excitation source for the driving element. According to the invention, the ultrasonic oscillator is designed as a hollow thin-walled piezoelectric cylinder, the height H of which is identical to or smaller than the mean diameter D thereof. The generators for ultrasonic vibrations are symmetrically disposed on both sides relative to the sectional plane S that extends through the center of the height of the ultrasonic oscillator, perpendicular to the longitudinal axis L thereof. The cylinder surface of the driving element is in contact with the driven element, and the electrical excitation source is connected to the ultrasonic linear drive unit in such a way that the drive unit excites only the first or the second generator for ultrasonic vibrations.

Ultrasonic linear drive unit comprising a hollow cylindrical oscillator

The invention relates to an ultrasonic linear motor () comprising a plate-type ultrasonic oscillator () with two planar parallel main faces, two end faces and two lateral faces and a displaceable element () that engages with at least one guide rail () and has two friction parts, said element interacting with the ultrasonic oscillator to cause friction via the lateral faces of the friction parts. The lateral faces of the ultrasonic oscillator are planar and are inclined at the same angle in relation to a longitudinal plane of symmetry, in such a way that the intersection lines between the planes of the lateral faces and the longitudinal plane of symmetry run parallel to the main faces of the ultrasonic oscillator. The friction parts of the displaceable element are interconnected by springs.

Ultrasonic linear motor

The invention relates to a linear ultrasound piezoelectric motor comprising a mobile element that is in frictional contact with a plate-like rectangular resonance plate, wherein the frictional surface is embodied by means of at least one of the longitudinal narrow sides of the resonance plate, and electrodes for producing acoustic vibrations which are arranged on the longitudinal wide sides of the resonance plate. According to the invention, the generator for producing acoustic vibrations is asymmetrically arranged in relation to a plane which symmetrically cross-cuts the resonance plate, and comprises two opposing electrodes generating a stationary asymmetrical space wave when excited.

Linear ultrasound motor

The invention relates to a miniaturizable motor () comprising a rotor () that is driven by a hollow cylindrical piezo oscillator (). Said rotor is effectively connected to a frictional face () of the piezo oscillator while a main electrode or counter electrode () and excitation electrodes () are disposed on the surface of the hollow cylinder. The hollow cylindrical piezo oscillator is made of a monocrystalline material with a trigonal crystal system which is provided with three main electrical axes that are placed at a 120&#xb0; angle relative to each other as well as an optical axis. Said optical axis encloses a 90&#xb0; angle along with the point of intersection of the electrical axes while coinciding with the longitudinal axis of the hollow cylindrical piezo oscillator. Furthermore, the axial axis of symmetry of the respective excitation electrode intersects one of the main electrical axes while said axial axis of symmetry extends parallel to the optical axis.

Miniaturizable motor

The invention relates to an ultrasound linear piezoelectric motor comprising an ultrasound oscillator () embodied in the form of a piezoelectric plate () or a cylinder shell part (), acoustic oscillation generators () and a friction element () which frictionally interacts with a driven element () and is disposed in a holder. The inventive holder is embodied in the form of an elastic clamp () which embraces a driven element, is fixed to the ultrasound oscillator and made of a sound-conducting material.

The invention relates to a piezoelectric ultrasound motor with an oscillator in the form of a piezoelectric plate of the length L and the height H as well as with one or two friction elements which are arranged at the oscillator and elastically pressed against the friction surface of the part to be moved. According to the invention, the piezoelectric plate is divided into two identical parts by a section plane extending vertically to the large surfaces, with at least one of these parts including an asymmetrical generator of an asymmetrical acoustic standing wave, which upon its activation generates an asymmetrical two-dimensional standing wave, so that the friction elements which are arranged in the center of the long end face of the plate carry out a movement with an inclination relative to the end face, so that the energy of motion is transferred to the element to be moved.

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Woerth, Germany

Alexej Wischnewskij