WO1992010874A1

WO1992010874A1 - Piezoelectric motor

Info

Publication number: WO1992010874A1
Application number: PCT/SE1991/000807
Authority: WO
Inventors: German Alexandrovich Chesnokov; Dmitry Pavlovich Kolesnikov; Victor Alexeevich Ivanov; Valery Aronovich Kotov
Original assignee: Scansov Transport Ab
Priority date: 1990-12-04
Filing date: 1991-11-27
Publication date: 1992-06-25
Also published as: EP0513288A1; CA2075032A1; JPH05503834A

Abstract

A piezoelectric motor comprising a stator (1) with a piezoelectric oscillator and a rotor (2), the piezoelectric oscillator having a piezoelectric element (12) with electrodes (13), and pushers (15). Each pusher is provided with a spring (16) by means of which it is arranged on a collector (18, 19) being mounted on the body coaxially with the piezoelectric element (12). Each pusher by one end keeps mechanical contact with the piezoelectric element (12) under the action of the spring and by other end abuts a surface of the rotor at an acute angle. The springs of all pushers may be orientated in one direction circumferentially or in opposite direction (for adjacent pairs of pushers). Furthermore, to allow a reverse of the motor, the pushers are divided into two groups, in each group the pushers contact the surface of the rotor in opposite directions.

Description

PIEZOELECTRIC MOTOR (Specification)

FIELD OF THE INVENTION

The present invention relates to piezoelectric devices and, more particularly, to piezoelectric devices of a preferably rotational movement type. A motor may be used as a low-speed gearless drive of different mechanisms such ones as tape transport mechanisms of tape-recorders, input-output apparatus, alpha-numeric printers peristaltic pumps of medical usage, in an automotive industry as drives of windscreen wipers, glass-frame risers and others.

PRIOR ART It is known a piezoelectric motor (US patent N 3211931,

US. C1.310-8.3, published October 12, 1965) comprising a stationary mounted piezoelectric oscillator of torsional vibrations which is a cylindrical element made of piezoelectric ceramics and polarized in a specific manner, with electrodes provided on his end surfaces; and a driven element - a rotor being rotationally mounted in alignment with him. on free ends of the piezoelectric element are fixed pushers the free end of which are bended-off and interact with a surface of the rotor at an acute angle. When applying an alternating voltage to the electrodes of the oscillator the free ends of hollow cylindrical piezoelectric elements supported as a cantilever perform torsional vibrations (in a circumferential direction). These vibrations are transformed through the pushers into a unidirectional rotational movement of the rotor in a manner like that which takes place in a ratchet-and-pawl mechanism.

A drawback of the above piezoelectric motor is significant dimensions of the piezoelectric element (the length of the cylinder) stipulated by necessity to obtain angular displacements of the fee ends of the piezoelectric element to be sufficient for the operation of the motor.

To overcome such drawback in the piezoelectric motors are used the oscillators with piezoelectric elements made in form of a solid disk or a ring with electrodes and polarized in such a manner that when applying an alternating voltage to the electrodes radial vibrations take place in the piezoelectric element.

It is known a piezoelectric motor (USSR. A.C N 1278994, Int. CL H O2N2/00, filed July 5, 1974, published December 23, 1986) comprising two coaxially mounted cylindrical elements one of which is made of a piezoelectric active material with electrodes, and pushers, each pusher being fixed on one of the above elements made of a piezoelectric non-active material at an acute angle with its surface; a free end of the pusher interacts with a surface of other element made of a piezoelectric active material also at an acute angle with its surface. On the surface of the cylindrical element made of the piezoelectric active material interacting with the ends of the pushers is coated a wear-resistant layer acoustically coupled with the piezoelectric element.

When applying an alternating voltage to the electrodes of the piezoelectric element in the last take place radial vibrations, and during interaction of the surface of the piezoelectric element with pushers originates constant torque setting the motor in rotation.

A drawback of the above motor is a necessity to apply a wear-resistant layer on the surface of the piezoelectric element interacting with the pushers since, firstly, the presence of such layer results in a partial absorption of acoustic vibration energy of the piezoelectric element reducing the motor efficiency and, secondly, is the reason of low reliability since a breakdown of coupling of the layer with the piezoelectric element puts the motor out of order. Moreover, upon wearing the above layer it is requested to change an oscillator assembly.

It is known a piezoelectric motor (British patent application N 2118374 A, Int. C1. H O2N11/00, published October 26, 1983) comprising a stator, a rotor frictionally interacting with the stator having a body, a piezoelectric oscillator of radial vibrations being mounted on the body and comprising a piezoelectric element mounted coaxially with the rotor and made in form of a disk (a ring) with electrodes and, at least, two pushers each of which is fixed by one end on cylindrical surface of the piezoelectric element while by other end abuts the rotor. The pushers are fixed on the piezoelectric elements by two ways:

a) directly in a material itself in grooves on a periphery of the piezoelectric element (for example, with help of glue);

b) on a ring-casing being placed on outer side of the piezoelectric element; a tightness of connection of the ring-casing with a material of the piezoelectric element is achieved by usage of a forced fit of by some other way (for example, by a glue fixing the ring on a cylindrical side surface The pushers are fixed to such ring or radial slots by means of soldering, or by welding to its outer surface.

Drawbacks of the above piezoelectric motor result from a manner of fixing the pushers to the piezoelectric element and are the following: a) Fixing of pushers directly in the material of the piezoelectric element reduces dimensions of an active region of the element since a circular portion of the piezoelectric element in which one are made radial slots for placing pushers in fact proves to be passive one;

b) Fixing of pushers in radial slots on a periphery of the piezoelectric element with help of different solders, compounds is a mechanically non-reliable way; moreover, the presence of such material to be different from a material of the piezoelectric element in respect of physical properties between pushers and the piezoelectric element (even in form of a thin layer) deteriorates a transmission of vibrations from the piezoelectric elements to pushers reducing the apparatus efficiency;

c) The slots in the piezoelectric element for fixing of pushers in operational mode of the piezoelectric element are the source of the microcracks causing the break-down of this element herewith reducing an operating resource of the piezoelectric motor;

d) A usage of ax. outer metallic ring as an intermediate element for mounting pushers complicates a joint, makes it non-reliable;

- when assembling by a forced fit. the outer ring on the piezoelectric element in the last originate internal stresses. This leads to reduction of the motor efficiency since a part of applied electrical energy is consumed for compensation of a ring resistance and as a result is unnecessarily dissipated in form of heat increasing a temperature of a working body of the motor. Arises, moreover, difficult to be solved problem of a selection of a ring material possessing an agreed with piezoelectric ceramics value of a coefficient of thermal expansion as well as necessary elasticity and flexibility;

- connection of the outer ring on which are fixed the pushers with the piezoelectric element by means of glue. solder (or other compound) introduces an intermittent layer deteriorating a transmission of vibrations from the piezoelectric element to pushers reducing thus the apparatus efficiency.

stationary fixing, moreover, of pushers on the piezoelectric element (or a ring) narrows functional and technological capabilities for obtaining motors of one standard size with different characteristics (a rotational speed, a shaft torque and so on).

Therefore the first aim of the invention is to increase reliability and economy of a piezoelectric motor as well as to widen functional capabilities due to increasing a degree of unification.

It is the second aim of the invention to simplify and to reduce dimensions of the piezoelectric motor.

One more drawback of the motor in accordance with the patent application N 2118374 A, as well as others cases mentioned above is a unidirectivity of rotation stipulated by fixing all pushers in their invariable inclined position to the surface of the motor.

It is known, however, a piezoelectric motor of a reversible action - Sweden patent application N 452933, Int.Cl. H O2 N2/00 filed April 5, 1982 and published October 6, 1983. The motor comprises two coaxially mounted piezoelectric elements with electrodes and pushers, one of the piezoelectric elements is mounted stationary on a stator, while the other - on an output shaft, herewith an electrical contact of electrodes of movable piezoelectric element is realized with help of slip-rings and brushers. The pushers on the piezoelectric elements are bent to one side and interact with intermediate rotor in form of a cylinder.

When applying an alternating voltage to electrodes of stationary piezoelectric element its pushers turn the intermediate rotor and further the output shaft with movable piezoelectric element through the action of his pushers bended in the direction of movement of the intermediate rotor. When applying a voltage to electrodes of movable piezoelectric element the pushers interacting with stationary intermediate rotor being braked by pushers of stationary piezoelectric element turn movable piezoelectric element with output shaft in an opposite direction. When the voltage is absent on both piezoelectric elements the motor is braked.

Drawback of this motor - a complexity of a structure since it comprises a second piezoelectric element, slip-rings and the intermediate rotor; as well as a limited torque since a passive group transferring the torque operates as a friction coupling.

Therefore it is the third aim of the invention to provide a reverse of the piezoelectric motor.

DISCLOSURE OF THE INVENTION

Achievement of the first aim of the invention provides for creation of a piezoelectric motor of such design implementation which could allow, due to detachable connection of pushers with a piezoelectric element to increase reliability of a motor (his operating resource), an economy (an efficiency) as well as to widen functional capabilities of motors due to increase of a degree of unification.

The first aim of the invention is achieved by the fact that a piezoelectric motor comprising a stator, a rotor frictionally interacting with the stator having a body, a piezoelectric oscillator of radial vibrations being mounted on the body and comprising a piezoelectric element mounted coaxially with the rotor and made in form of a disk or a ring with electrodes, and pushers each of which by one end mechanically contacts the piezoelectric element and by other end - contacts the rotor at an acute angle to its surface, in accordance with the present invention additionally comprises a collector made in form of a ring with seats and fixedly mounted on the body coaxially with the piezoelectric element, the pushers are provided with springs by means of which the pushers interact with the collector (are fixed in the seats of the collector).

Besides, in accordance with the present invention the springs of pushers are orientated in one direction circumferentially.

In accordance with the present invention the springs of adjacent pushers are oriented, moreover, circumferentially in opposite direction.

The present invention characterized also in that each pair of adjacent pushers is provided with one doubled spring.

Herewith, in accordance with the present invention the springs of the pushers, being a single pusher or combined ones into the pair of the pushers, are made in form of bended portions of pushers plates.

The present invention characterized, moreover, in that the pair of the adjacent pushers is π-shaped and provided with additional springs made in form of a pair of symmetrically bended plates (two single ones or combined into the pair) arranged between the adjacent pushers.

The present invention allows to increase reliability of the piezoelectric motor due to excluding permanent connections of the pushers with the piezoelectric element, to increase his efficiency, maintainability (due to increase of modularity of structures).

Besides, the present invention allows to produce piezoelectric motors with unified structure components - piezoelectric elements (oscillators), units of pushers possessing different characteristics with unified dimensions that will allow to widen characteristics range of motors.

Achievements of the second aim of the invention provides for creating of a piezoelectric motor with such structure performance which could allow, because of using a collector - with elastic teeth-springs, fixing pushers on the surface of the piezoelectric element, to simplify the motor, reduce his radial dimensions, increase reliability.

The second aim of the invention is achieved by the fact that in a piezoelectric motor in accordance with the first variant comprising a rotor, a stator with

a piezoelectric element and a ring collector placed between the piezoelectric element and the rotor and having pushers being fixed on it by means of fastening springs the collector in accordance with the present invention is made in form of a set of teeth-springs elastically pressed to the piezoelectric element and mounted on a plane metallic ring being placed on the stator parallel to the piezoelectric element, the fastening springs of pushers are arranged between the piezoelectric element and the teeth- springs.

Besides, the pushers in accordance with the invention are π-shaped and their connectors are arranged between the piezoelectric element and the teeth-springs of the collector.

Achievement of the third aim of the invention provides for creation of a piezoelectric motor with such structure, performance which could allow, because of using two groups of pushers which are mounted non-unidirectively in respect to a surface of a rotor and capable to interact alternately with the motor, to reverse the motor.

The third aim of the invention is achieved by the fact that in a piezoelectric motor comprising a stator, a rotor frictionally interacting with the stator having a body, a piezoelectric oscillator of radial vibrations being mounted on the body and comprising a piezoelectric element mounted coaxially with the rotor and made in form of a disk with electrodes, and pushers each of which by one end mechanically contacts the piezoelectric element and by other end - interacts with the rotor at an acute angle, in accordance with the present invention the pushers are divided into equal groups, in each group the pushers contact the surface of the rotor at acute angles in opposite directions, the motor additionally comprises dogs arranged between the pushers circumferentially and movably for interaction with the pushers, i.e. for putting thus the pushers out of contact with the rotor.

Herewith, in accordance with the present invention the dogs interact, in ultimate positions, with the pushers of one of two groups of pushers putting them out of contact with the rotor.

Besides, in accordance with the present invention the dogs interact simultaneously in central (neutral) position, with the pushers of both non-unidirectively oriented groups putting them out of contact with the rotor.

The present invention allows to provide a reverse of the piezoelectric motor due to alternative putting into contact with the surface of the rotor the non-unidirectively oriented groups of the pushers; besides, due to simultaneous contact of both groups of the pushers in central position of the dogs, may be provided a fixation of the motor when it is switched off, i.e. braking in a definite position of the motor and a mechanism being coupled with it.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention is clarified by concrete examples of its embodiment and the accompanying drawings and wherein;

Fig.1 shows a first variant of a piezoelectric motor with a cylindrical outer rotor embracing pushers which are pressed to him in accordance with a first aim of the invention, and a longitudinal section π-π of Fig.1;

Fig.2 shows a piezoelectric motor, a cross-section along a line I-I of fig.1 in accordance with the invention;

Figs.3a, 3b show a pusher with a fastening spring made in form of a bended end of a pusher plate in accordance with the invention;

Figs.4a, 4b show a pusher with fastening springs made in form of bended cut side edges of a pusher plate in accordance with the invention;

Figs.5 and 6 show doubled pushers, with fastening springs made in form of bended middle part of pushers plate in accordance with the invention;

Fig.7 shows a doubled pusher fastening springs of which are made independent ones in accordance with the invention;

Figs.8a - 8e depict variants of embodiment of one of two fastening springs of the doubled pusher shown in Fig-7 in accordance with the invention;

Figs.9a - 9d depict various kinds of fixing single pushers in accordance with Figs.3a and 3b and doubled pushers in accordance with Figs.5,6 and 7;

Figs.10a and 10b depict a variant of fixing the doubled pusher in accordance with Fig.7;

Fig.11 show fixing the doubled pusher in a piezoelectric motor with an outer ring element and a rotor placed within it in accordance with the invention;

Figs.12a - 12d show one of variants of structure elements of a collector as well as manners of fixing a collector to a body of a piezoelectric motor and connecting the structure members therebetween in accordance with the invention;

Fig.13 shows a second variant of a piezoelectric motor with a cylindrical outer rotor embracing pushers which are pressed to him in accordance with the second aim of the invention, a longitudinal section π-π of Fig.13; Fig.14 shows a piezoelectric motor a cross-section along a line I-I of Fig.13 in accordance with the invention;

Figs.15a and 15b show fragments of blanks of collectors for a piezoelectric motor with the an outer rotor (Fig.16a) and with inner or outer rotor (Fig.15b) in accordance with the invention;

Figs.16a - 16c depict mutual location of a collector with a piezoelectric element in structures with outer arrangement of a rotor (Figs.16a, 16b) and inner arrangement of a rotor (Fig.16a);

Fig.17 shows a third variant of a piezoelectric motor with a cylindrical outer rotor embracing pushers which ones being non-unidirectively oriented are pressed to him and have dogs for interaction with the pushers in accordance with a third aim of the invention, a longitudinal section π-π of Fig.18;

Fig.18 show a piezoelectric motor, a cross-section along a line I-I of Fig.17 in accordance with the invention;

Figs.19a - 19d depict various diagrams of interaction of dogs with pushers in central and ultimate positions of the pushers in accordance with the invention;

Figs.20a - 20e show one of possible variants of a device for turning a ring with dogs and his fixation in central and ultimate positions in accordance with the invention;

Fig.21 depicts mutual location of structure elements of a piezoelectric motor with a central rotor and outer ring-shaped piezoelectric element in accordance with the invention. DETAILED DESCRIPTION OF THE INVENTION

A piezoelectric motor in accordance with the first variant of embodiment (Figs.1, 2) comprises a stator 1 - stationary part of the piezoelectric motor in respect of an article (not shown in figures) and a rotor 2 supported rotatively on the stator 1 with help of a bearing (a bush) 3. Against axial displacement the rotor is fixed on a rotor shaft 5 by means of a shoulder 4 and a lock washer 6.

The stator 1 of the piezoelectric motor comprises a piezoelectric oscillator 7 of radial vibrations acoustically insulated from a body 8 by means of gaskets 9 of elastic material (for example, rubber) and fixed on it with help of a nut 10. The body 8 protects the piezoelectric oscillator 7 and other elements of the motor against damage, as well as support the piezoelectric motor in the article with help of fastening holes 11.

The piezoelectric oscillator 7 of radial vibrations is an electromechanical device for conversion of electrical energy to mechanical one of oscillatory preferably in radial direction, motion of particles of active element of the piezoelectric oscillator 7 - a piezoelectric element 12 made in form of a body of revolution. For originating radial vibrations in the piezoelectric oscillator 7 the piezoelectric element 12 is made in form of a flat ring (a desk with holes) manufactured of a material possessing piezoelectric properties, with electrodes 13 on flat surfaces of the ring provided with terminals 14. The electrodes are a thin metal coating on a ground surface of the piezoelectric element 12 which may be obtained, in particular, by spraying a metal, chemical sedimentation of a metal up to necessary thickness of electrodes. Alternating voltage from a power source (not shown in Fig.1) is applied to the electrodes 13 through the terminals 14 which are soldered to the electrodes as shown in Fig.1. (The terminals may be connected also by a contact method.) Pushers 15 contact outer cylindrical surface of the piezoelectric element 12 and abut inner surface of the rotor 2 at an acute angle with other end. Fixing of the pushers to the body is made with help of springs 16 by which is provided each pusher individually as shown in Fig.2 (see also Figs3a, 3b 4a, 4b). Direct contact of each ends of pushers 15 with the surface of the piezoelectric element 12 without intermediate binding materials (solder, glue epoxy compounds etc.) eliminates energy losses in thin layer of the above materials placed between the pushers and the surface of the piezoelectric element allowing to increase the motor efficiency and reliability due to stability of direct contact of the pushers with the piezoelectric element.

The pushers may comprise a spring element 16 which is a part of a plate-blank which is bended in a specific manner (see Figs.3a, 3b, 4a, 4b). Ends 17 of springs 16 of the pusher 15 are supported in a collector made of two structure elements 18, 19 (Figs.1, 2) which provides for axial and circumferential fixation of the pushers; such fastening does not hinder the end of the pusher from a radial displacement which one directly contacts the surface of the piezoelectric element 12.

Pushers may be made as single ones (Figs.2, 3a, 3b, 4a and 4b) or doubled.

The springs 16 for fastening the pushers may be made as a banded part of the plate-blank as shown in Figs.3a, 3b, 4b. 5 and 6 or as separate parts (Figs.7,8). In last case to prevent an axial displacement of the pushers on ends of such springs are made slots (Fig.8b) or angles of such springs are bended outward (Figs.8c, 8d, 8e).

Each pusher is made of flat (sheet) elastic sound conducting material, for example, of steel, brass, phosphor bronze.

Single pushers 15 ( Figs.3a, 3b) may be mounted with help of springs 16 being oriented in one direction as shown in Fig.2, or in opposite direction as shown in Fig.9a. Examples of mounting the doubled pushers (Figs.5, 6, 7) in the collector are given in Figs.9b - 9d, 10a and 11.

To the body 8 of the piezoelectric motor as assembled unit of the structure elements 18, 19 of the collector with pushers is fixed by means of several screws 20 (see Figs. 12c, 12d). The parts 18, 19 of the collector are connected therebetween by tightening screws 21 with washers 22; herewith the ends 17 of springs 16 are rigidly pressed between flat surfaces of the parts 18, 19 that provides for fixation of the pushers in an axial direction.

To simplify mounting the pushers unit on the oscillator a wedge clamp of the pushers ends by the part 19 (Fig.12a) may be provided. In such a case the pushers unit with the part 18 is freely mounted in the body 8 of the piezoelectric element and is fixed to it by means of screws 20, after that the ends 17 of springs 16 of the pushers are finally clamped by a conic portion of the part. 19 as shown in Fig.1.

The proposed diagram of fixing the pushers by means of the springs 16 mounted with the ends 17 in the collector (structure element 16) widens possibilities of unification of the motors: since the motor is made of separate independent units - a stator with a piezoelectric elements, a pushers unit in a collector, a motor whose parameters (in particular, a thickness of a piezoelectric element and power accordingly) may be changed. Herewith, in one collector it is possible to mount pushers 15 of a different width corresponding to a thickness of a piezoelectric element 12 since pushers being different in width may be provided with springs whose fastening ends 17 have equal width. In other variant of embodiment of a collector the unification may be achieved by usage if intermediate rings for ensuring fixation of pushers having different width of the fastening ends 17 of the springs. Clamping of pushers 15 to the rotor 2 and the piezoelectric element 12 is realized due to force of elastic deformation of pushers themselves. To the piezoelectric element 12 are pressed pushers additionally by their springs 16. This ensures guaranteed mechanical contact of pushers 15 with the piezoelectric element 12 when the last performs radial vibrations.

To ensure uniform mechanical load applied to the piezoelectric element the number of pushers should be at least two single ones or two doubled ones accordingly at uniform arrangement of them circumferentially.

Radial clearances between the piezoelectric element 12, the collector 18, 19 and the rotor 2 accordingly and a length of pushers are scaled up schematically in Figs.1, 2, 9a - 9e, 10a and 11; in reality the length of pushers should be less to increase its rigidity to lateral bending. Herewith the spring 16 of pushers should have lesser radial dimensions to prevent circumferential displacement of pushers ends interacting with the surface of the piezoelectric element: their position should be near to a tangent line in a point of contact of the pusher end with the piezoelectric element.

Rot or 2 of the piezoelectric motor (Fig.1) comprises three main parts - the shaft 5, a cup 23 assembled by a forced fit on it and a frictional part - a ring insert 24 which fictionally interacts with pushers 15. The frictional part is made of wear-resistant material; its operating surface should have minimum roughness to reduce wear of pushers. The shaft 5 of the rotor 2 is mounted in the bearing-bush 3 made of antifrictional material.

The piezoelectric motor may be performed also with an internal rotor, i.e. be placed inside a ring piezoelectric element. In such case doubled pushers are made not divergent ones, as shown, for example, in Figs.5, 6 and 7, but convergent ones; manner of their fixation and fastening parts do not differ from the written above, with the exception of a shape of the parts itself (see Fig.11).

The piezoelectric motor operates as follows. When applying to the electrodes 13 of the piezoelectric oscillator 7 an alternating voltage of the definite frequency - equal to or approximating to the resonance frequency of longitudinal and radial vibrations of the piezoelectric element 12 in the last originate the longitudinal radial vibrations. These vibrations are transmitted to pushers 15.

When the piezoelectric element 12 is extended his surface moves in a radial direction inner ends of the pushers 15 which mechanically contact the surface Opposite ends of the pushers being in the frictional interaction with the cylindrical surface of the frictional element 24 of the rotor 2, due to a wedging, create on the rotor a tangential force (since an angle between the pusher and the line tangent to the surface of the rotor is less than 90 ) that results in turning the rotor through some angle.

From the circumferential displacement of inner ends of pushers 15 being in a mechanical contact with the cylindrical side surface of the piezoelectric element 12 hinder the springs 16 of pushers, by means of which the pushers are fixed on the collector which one is a part of the stator, as well as the frictional force between them and the surface of the piezoelectric element which one is also a part of the stator.

Besides, a fixation of pushers in circumferential direction may be realized by the collector in whose seats are mounted pushers (see Figs. 9d, 10d).

When the piezoelectric element 12 is compressed inner ends of pushers 15 move in a radial direction to a center of the piezoelectric element under the action of an elastic force of as the pushers themselves and the force of their fastening springs 16. More outer ends of pushers 15 interacting with the surface of the frictional element 24 of the rotor 2 for a moment lose contact with the said surface and pushers 15 under the action of elastic forces straighten themselves, and the ends of pushers occupy a new position in the circumferential direction of the rotor, or, because of decrease of a clamping force of the ends (without loss of contact with the surface of the frictional element 24) and decrease of a frictional force accordingly, the ends of pushers slip on the surface of the frictional element and occupy the new position in the circumferential direction of the rotor. From a reverse turn of the rotor 2, because of action of frictional forces between the surface of the frictional element and the ends of pushers 15 slipping on it in the circumferential direction may hinder largely inertial forces of a mass of the rotor and masses of a driven in rotation mechanism being connected with it.

Such process repeats oneself at vibrations of the piezoelectric element 12 and is accompanied by origin of constant torque setting the rotor 2 of the piezoelectric motor in rotation.

A second variant of embodiment of a motor will be written with reference to accompanying Figs.13 - 16.

A piezoelectric motor in accordance with the second variant of embodiment (Figs.13, 14) comprises also a stator 1 and a rotor 2, a piezoelectric element 12 and pushers 15 fixed on a collector.

The second variant of embodiment of the piezoelectric motor differs structurally from the first one by the following.

The collector of the piezoelectric motor is made in form of a set of teeth-springs 25 elastically pressed to a working cylindrical surface of the piezoelectric element 12 and mounted on a metallic disk 26 being placed on the stator. The fastening springs 16 of pushers are arranged between the piezoelectric element 12 and the teeth 25 which closely press the pushers to the surface of the piezoelectric element as well as fix the pushers in circumferential and axial directions.

The collector is manufactured of a blank 26 of elastic sheet metal (for example, of steel) having figured slots in radial direction forming teeth 25 (see Fig. 15a). These teeth are bended perpendicularly to a plane of the blank of the collector and are banded along longitudinal axes over an arc of a circle with a radius not exceeding a radius of the piezoelectric element Teeth-springs are also bended in longitudinal direction in order a contact of the teeth-springs with connectors 16 takes place on middle (in respect of height of the piezoelectric element) part of the connector (see Figs.16a - 16c).

Teeth 25 of the collector are provided with shelves 27 ensuring fixation of pushers placed in space between them in axial direction.

Such collector is designated for a piezoelectric motor with outer rotor; it is mounted under the piezoelectric element as shown in Fig.13. From the piezoelectric element it is separated by insulating pad 28.

The collector may be manufactured of a blank in form of a disk with teeth on its inner side (see Fig.16b). Such collector may be used in a piezoelectric motor as with outer motor (see Fig.16b) and with inner arrangement of the rotor (see Fig.16c). A difference in such case is largely in a direction of bending of teeth-springs.

In the proposed structure of fixing pushers by means of such collector the last functions as springs which realize clamping the pushers to the piezoelectric element with a given force providing a close contact. Since the contact of pushers with the piezoelectric element is realized with help of the connector 16 having a large contact stresses in a material of the piezoelectric element are reduced. Usage of such collector allows to reduce radial dimensions of the motor or to increase dimensions of the piezoelectric element with unchanged dimensions of the motor that ensure an increase of motor power.

The piezoelectric motor may be made also with inner rotor, i.e. the rotor arranged inside the ring piezoelectric element 12. In such case a ring part 26 of the collector is placed under the ring piezoelectric element and his teeth damp connects of pushers 15 to inner cylindrical surface of the piezoelectric element (see Flg.16c).

The second variant of the piezoelectric motor operates analogically to the first one.

As and in the first variant of the piezoelectric motor from the circumferential displacement of inner ends of pusher 15 with connectors 16 being in a mechanical contact with the cylindrical side surface of the piezoelectric element 12 hinder teeth-springs 25 of the collector. From the axial displacement of pushers hinder shelves 27 on teeth-springs 25 of the collector in space between which are placed pushers 15.

A third variant of embodiment of a motor will be written with reference to accompanying Figs.17 - 21.

The third variant of embodiment of the piezoelectric motor of reversible type differs structurally from the first and the second non-reversible motors by the following.

His structure difference ensure the fact that his pushers 15 contacting by one end the outer cylindrical surface of the piezoelectric element 12 abut by other end the inner surface of the rotor 2 at an acute angle In opposite directions forming two non-unidirectively oriented groups.

Besides, in a ring area of the body 8 between the rotor 2 and the collector made of two structure elements 18-19 are provided elongated holes 29 spaced circumferentially in which ones are arranged dogs 30 mounted on a ring 31 being movable in circumferential direction and clamped to the body 8 by fixing ring 32 which Is fixed on the body 8.

The dogs 30 may be arranged on the ring 31 in a different manner so that, when turning the ring into ultimate positions, the dogs bend off pushers of one of the groups (see Figs.19c, 19d) from inner surface of the rotor 2, while at the central position of the ring the dogs either bend off pushers of both groups (FigJ.9a) or do not interact with pushers of both groups as shown in Flgs-18 and 19b.

The turn of the ring 31 may be realized from external driving means (not shown in figures) interacting in radial direction, for example, with a lever 33 (see Fig.20a) mounted on the ring 31.

In ultimate and central positions the ring 31 with dogs 30 is fixed with help of well known means, for example, a ball 35 being pressed by a spring 34 and mounted in a cage 36 which is secured on the body 8 of the motor, or a figured sheet spring 37 which ones interact with recesses in the ring 31 arrangement of which ones in circumferential direction corresponds to given positions of the ring; an additional restriction to turning the ring above the necessary rate may be realized as due to contact of dogs 30 with edges of holes 29 and due to stops 38 which are provided on the body 8 and interact with the lever 33 (see Figs.20a - 20c).

The piezoelectric motor may be performed as with an outer rotor (see Figs.17 -19) and with an internal rotor, i.e. be placed inside a ring piezoelectric element (Fig 21).

In such case holes 29 with dogs 30 are spaced circumferentially in a ring area between an inner rotor 39 with a frictional element 40 and the collector 18 - 19. Securing of the ring 31 with dogs 30 by means of a fixing ring 31 in such case does not differ, in essence, from the shown in Fig.17.

This variant of a reversible piezoelectric motor operates as follows. When turning the ring 31 with dogs 30 inco one or ultimate positions the dogs 30 bend off a group of pushers 15 interacting with them and put them out of contact with a surface of the rotor 2; other group of pushers keeps contact with the rotor.

When applying alternating voltage to the electrodes 13 of the piezoelectric oscillator 7 the direction of rotation of the rotor will be determined by that which group of pushers keeps contact with the rotor.

When the ring 31 with dogs 30 is in the central position a status of the motor will be determined by a scheme of interaction of dogs 30 with pushers 15 (see Figs.18, 19b); if both groups of pushers are simultaneously bended-off the motor will be switched-off and not braked even in the presence of voltage on the electrodes 13; if both groups of pushers interact simultaneously with the rotor (see Figs.18, 19a) the motor will be braked as in the absence and in the presence of voltage on the electrodes 13.

Claims

WHAT IS CLAIMED IS

1. A piezoelectric motor comprising a stator, a rotor frictionally interacting with the stator having a body, a piezoelectric oscillator of radial vibrations being mounted on the body and comprising a piezoelectric element mounted coaxially with the rotor and made in form of a disk or a ring with electrodes, and pushers, each of the pusher by one end mechanically contacts the piezoelectric element and by other end contacts the rotor at an acute angle to its surface, c h a r a c t e i z e d in, that to improve reliability and economy as well as to widen functional capabilities of the motor due to increase of a degree of unification,

additionally comprises a collector made in form of a ring with seats and fixedly mounted on the body coaxially with the piezoelectric element, the pushers are provided with springs interacting with the collector.

2. A piezoelectric motor according to claim 1, wherein the springs of pushers are oriented circumferentially in one direction.

3. A piezoelectric motor according to claim 1, wherein the springs of adjacent pushers are oriented circumferentially in opposite direction.

4. A piezoelectric motor according to claim 3, wherein a pair of adjacent pushers is provided with one spring interacting with the collector.

5. A piezoelectric motor according to claim 1 or 4, wherein springs of pushers are made in form of bended portions of pushers plates.

6. A piezoelectric motor according to claim 4, wherein the pair of adjacent pushers is π-shaped and provided with additional springs made in form of a pair of symmetrically bended plates arranged between adjacent pushers.

7. A piezoelectric motor according to claim 1, c h a r a c t e r i s e d in, that to simply a structure of the motor and to reduce his dimensions, the collector is made in form of teeth-springs elastically pressed to the piezoelectric element and mounted on a plane metallic ring being placed on the stator parallel to the piezoelectric element, the springs of pushers are arranged between the piezoelectric element and the teeth of the collector.

8. A piezoelectric motor according to claim 8, wherein the pushers are π-shaped and their connectors are arranged between the piezoelectric element and the teeth-springs of the collector.

9. A piezoelectric motor comprising a stator, a rotor frictionally interacting with the stator having a body, a piezoelectric oscillator of radial vibrations being mounted on the body and comprising a piezoelectric element mounted coaxially with the rotor and made in form of a disk or a ring with electrodes and pushers, each pusher by one end mechanically contacts the piezoelectric element and by other end - interacts with the rotor at an acute angle to its surface, c h a r a c t e r i z e d in, that to allow a reverse of the motor, the pushers are divided into two groups, in each group the pushers contact the surface of the rotor in opposite directions, the motor additionally comprises dogs arranged between the pushers circumferentially and movably in circumferential direction for interaction with the pushers.

10. A piezoelectric motor according to claim 9, wherein at ultimate positions of the dogs the pushers of one of the two non-unidirectively oriented groups accordingly are put out of contact with the rotor.

11. A piezoelectric motor according to claim 10, wherein at central position of the dogs the pushers of both non-unidirectively oriented groups are put out of contact with the rotor.