WO2023241759A1

WO2023241759A1 - Ultrasonic motor

Info

Publication number: WO2023241759A1
Application number: PCT/DE2023/100444
Authority: WO
Inventors: Alexej Wischnewski
Original assignee: Physik Instrumente (Pi) Gmbh & Co. Kg
Priority date: 2022-06-13
Filing date: 2023-06-13
Publication date: 2023-12-21
Also published as: DE102022114863B3

Abstract

The invention relates to an ultrasonic motor comprising: at least one piezoelectric ultrasonic actuator (1) having at least one generator (12) for generating a planar acoustic travelling wave; an element (2) to be driven having an external thread; and a drive element (6) having an inner peripheral surface (7), that is provided with a thread (8), and an outer peripheral surface, the drive element being inserted into the ultrasonic actuator (1) so that an inner peripheral surface of said actuator surrounds the outer peripheral surface of the drive element (6), the element (2) to be driven and the drive element (6) being in threaded engagement, and it being possible to transmit the planar acoustic travelling wave from the ultrasonic actuator (1) to the drive element (6), thereby rotating the element (2) to be driven. The ultrasonic actuator (1) has the shape of a polygonal plate (4) having two large main surfaces (19) and at least three smaller lateral surfaces (18) that connect the two main surfaces (19) to one another, and said actuator comprises at least one active generator (13) for generating a planar acoustic standing wave, the oscillation velocity maximum of which is in the region of the inner peripheral surface of the ultrasonic actuator (1).

Description

ultrasonic motor

The invention relates to an ultrasonic motor.

Piezoelectric friction contact drives are known from the prior art, in which the friction contact is designed in the form of a threaded engagement. They can be used, for example, as spindle drives in various types of mechanisms, such as in linear drives, in precise closure and metering systems, in valves, in precise cutting drives, in control drives, in precise positioning devices, such as in technological coordinate tables, in multi-coordinate positioning devices, in tripods or hexapods , in optical laser systems and similar devices, and in precision medical devices, e.g. pumps, syringes, insulin pumps or devices for bone lengthening.

Lasers are used in many areas of technology, be it in metrology, medical technology, metal processing, etc. The laser beam is usually precisely directed or guided with the help of tilting mirrors. The required precision of laser beam steering is achieved with the help of micrometer screws. These are often operated manually. However, there are a number of applications in which manual adjustment of the tilting mirrors is not possible or undesirable, for example within a vacuum chamber, in a lithography machine or a tachymeter.

Piezoelectric friction contact drives are often used for automatic positioning of the tilting mirrors. Here, an element to be driven, i.e. the rotor or rotor, is connected or coupled to the actuator by a frictional contact, with a targeted deformation or movement of the actuator caused by electrical control being transmitted to the element to be driven by means of the frictional contact.

[0005] The applicant's DE 102009 049 719 A1 describes a plate-shaped actuator which is on its top side as well as on its The bottom has two electrodes spaced apart by a separation area, the electrodes on the top being arranged offset from the electrodes on the bottom.

[0006] From the applicant's DE 10 2016 110 124 A1 an ultrasonic motor is known which has a rectangular piezoelectric ultrasonic actuator on which two friction elements are arranged at a distance from one another, and the ultrasonic actuator is divided in the form of a plate into two pairs of diagonally opposite sections, wherein a part of an acoustic standing wave generator is arranged in each of the diagonal sections, and a total of two generators are present, each consisting of two parts that can be operated in antiphase.

US 2005/0275318 A1 discloses a stacked piezoelectric transducer in which the electrodes arranged on the respective surfaces of the individual layers have a design that differs from one another, which takes into account the different expansion behavior of the transducer along the stacking direction.

WO 2022/176560 A1 teaches a rotary ultrasonic motor in which a shaft to be driven is operatively connected to a rotor via a spring element, the rotor being driven via a vibrator in which traveling waves are generated.

[0009] From US 5 410 206 A and EP 2 676 361 B1, designs of an inertial drive are known in which the part to be moved is a screw. This is screwed into a threaded nut and is in frictional contact with it. The threaded nut is in turn connected directly or indirectly to a piezo actuator, which sets the screw in motion based on the principle of inertia. The main disadvantage of this inertia drive is a relatively low speed of the part or screw to be moved. This is due to the inertia-based drive principle of the motor. The piezo actuator cannot drive the screw faster than a few 10 kHz, because when a certain frequency is exceeded, the static friction between the actuator and the screw changes into sliding friction, which results in a relative movement or sliding comes between the actuator and the screw without the screw being driven and simply standing still.

From DE 10 2008 023 478 A1 an ultrasonic drive with a hollow cylindrical oscillator is known, the inner cylinder surface being in effective contact with an element to be driven.

US 4,734,610 A discloses a vibrating shaft motor having a circular vibrating member which has a thread and which is coupled to a unit which generates a traveling wave in the vibrating member, this traveling wave propagating along a circumferential direction of the vibrating member. A movable part is in effective contact with the vibration part and engages with its correspondingly designed thread in the thread of the vibration part.

DE 4438 876 B4 describes a piezoelectric motor with a stator on which a piezoelectric oscillator is arranged, and with a rotor, the rotor being in effective contact with the piezoelectric oscillator. The piezoelectric oscillator has three ultrasonic wave generators.

A piezoelectric ultrasonic motor with a threaded contact or with a threaded engagement between a driving element and an element to be driven is known from US Pat. No. 4,734,610 A. In one embodiment, the driving element is designed as a thin-walled nut made of metal and the element to be driven is designed as a threaded rod, the nut and the threaded rod being in frictional engagement. Thin piezoelectric discs are glued to the end faces of the nut. The mother takes on the task of the acoustic resonator, and the piezoelectric disks form the surfaces for the exciters of the acoustic traveling wave in the thin-walled mother. The acoustic traveling wave formed in the nut and the thread or friction contact between the nut and the threaded rod results in a rotation of the threaded rod, which ultimately results in a linear movement of the threaded rod. A disadvantage of the ultrasonic motor according to US 4 734610 A is that in the actuator of this motor the volume of the metal nut is significantly larger than the volume of the piezoelectric exciter. A small electromechanical coupling coefficient is therefore characteristic of such an actuator. Therefore, this motor only allows low movement speeds and a small pulling force, and also requires high excitation voltages. Because of the high electrical voltages, the actuator heats up significantly due to the electrical losses in the piezoceramic. This heating leads to a reduction in the operational safety of the engine.

The publication US 6 940 209 B2 discloses a piezoelectric ultrasonic motor with a threaded contact or with a threaded engagement between a driving element and an element to be driven. According to one embodiment, the driving element is a metal tube on which piezoelectric exciter plates are arranged. There is a threaded insert in the metal tube. The element to be driven is designed as a threaded rod and is in frictional engagement with the threaded insert. The metal tube represents an acoustic resonator, and the piezoelectric excitation plates arranged on it generate an elastic traveling wave in the tube, which is aligned longitudinally to the axial axis of the tube. The traveling wave is transmitted to the threaded insert, and the threaded or frictional contact between the threaded insert and the threaded rod results in a rotation of the threaded rod and thus ultimately a linear movement of the threaded rod.

[0016] The disadvantage of the motor known from US 6,940,209 B2 is that bending vibrations are used in it. This reduces the electromechanical coupling coefficient, which reduces the speed of movement and the pulling force. At the same time, the electrical excitation voltage increases. As in the case of the previously mentioned US 4 734610 A, at high excitation voltages it heats up due to the electrical losses in the Piezoceramic makes the actuator strong, which reduces the operational reliability of the motor.

Another disadvantage of the ultrasonic motors according to the publications US 4,734,610 A and US 6,940,209 B2 is the fact that their dimensions cannot be increased in order to achieve greater tensile and holding forces, which greatly limits their possible area of application.

From the generic DE 102010 022 812 B4 an ultrasonic motor based on the principle of electrical excitation of running ultrasonic waves in a piezoceramic actuator is known. The ultrasonic motor comprises at least one one-piece annular piezoelectric ultrasonic actuator with at least one generator for generating a plane acoustic traveling wave, a substantially annular contact element with an outer and inner circumferential surface and an element to be driven. The contact element is completely surrounded by the actuator on its outer peripheral surface. The contact element is provided with a thread on its inner peripheral surface and is in threaded engagement with the element to be driven which is provided with an external thread. The flat acoustic traveling wave created by electrical excitation in the actuator is transmitted to the contact element, so that the element to be driven rotates.

[0019] A disadvantage of the drive according to DE 10 2010 022 812 B4 is the fact that in order to counteract the torque developed by the motor during operation, the actuator is clamped on its outer peripheral surface with the aid of a holding element or is glued into it. This causes the actuator to be strongly damped, which means that the oscillation amplitude of the contact element becomes smaller and the torque and speed decrease. Therefore, the ultrasonic motor known from DE 10 2010 022 812 B4 requires a relatively high electrical voltage to operate, as a result of which the actuator becomes warm and the efficiency of the motor decreases. Another disadvantage of the ultrasonic motor according to DE102010 022 812 B4 is a low reliability of the adhesive connection of the contact element to the piezoelectric actuator when the diameter of the contact element is large. The contact element is glued into the piezoelectric actuator. With a relatively large outer diameter of the contact element (from approx. 60 mm), the size of the outer circumferential surface becomes critical for an adhesive connection. When the actuator is heated during operation, mechanical stresses arise in the adhesive boundary layer between the piezoelectric material of the actuator and the metallic or ceramic contact element due to different expansion coefficients, which can cause the adhesive to fail. In such a case, the contact element can no longer transmit the movement to the element to be driven.

The object of the invention is therefore to provide an ultrasonic motor which overcomes the disadvantages of the ultrasonic motors known from the prior art and which in particular has a high level of efficiency and can therefore be operated with a comparatively low electrical voltage, so that it can be operated during is heated only slightly or not at all during operation, which ensures high operational reliability. Furthermore, it is an object of the invention to provide an ultrasonic motor that can be operated with a simply constructed and therefore more cost-effective electrical excitation device.

[0022] This object is achieved by an ultrasonic motor according to claim 1, the subsequent subclaims describing at least useful developments.

The ultrasonic motor according to the invention has at least one piezoelectric ultrasonic actuator, which comprises or contains at least one generator for generating a planar acoustic traveling wave. Furthermore, the ultrasonic motor according to the invention has a drive element and an element to be driven by the drive element, the drive element having a threaded inner peripheral surface and thus an internal thread, as well as a Has outer circumferential surface, and wherein the drive element is inserted into the ultrasonic actuator and preferably glued into it such that an inner circumferential surface of the ultrasonic actuator surrounds or surrounds the drive element on its outer circumferential surface. The element to be driven has an external thread which engages with the internal thread of the drive element and through the thread engagement the planar acoustic traveling wave generated by the generator of the ultrasonic actuator can be transferred from the ultrasonic actuator to the drive element, whereby a rotation of the element to be driven can be caused .

The actuator of the ultrasonic motor according to the invention is designed as a polygonal plate or polygonal disk, i.e. as a plate or disk whose thickness is significantly smaller than its remaining dimensions, the plate or disk having a polygonal shape. The polygonal plate or disk has two large main surfaces and at least three smaller side surfaces or peripheral surfaces connecting the two main surfaces. Due to the polygonal shape of the actuator and the resulting eigenmodes for standing waves, it is particularly possible to fasten the actuator or the polygonal plate in a holder with low losses and without strong damping.

The ultrasonic actuator or the polygonal plate has at least one active generator for generating a planar acoustic standing wave. The specific standing waves that can be generated in this way have the advantage that the maximum of their vibration amplitudes in the radial and circumferential directions is present essentially on the thread surface or in the area of the thread surface of the drive element inserted into the actuator and coupled to it, so that the drive energy of the drive element is extremely efficient can be transferred to the element to be driven which is in threaded engagement with it.

[0027] If the indefinite article is used for a feature in the text - as above and possibly also below - then this will be the case a subsequent mention of the same feature by using the definite article explicitly refers to the quantity information implied by the indefinite article, without this being intended to lead to a corresponding restriction to this precise quantity information.

It can be advantageous that the contour of the polygonal plate has the shape of a triangle with three side or circumferential surfaces or a square or a rectangle each with four side or circumferential surfaces or a pentagon with five side or circumferential surfaces or a hexagon with six side or peripheral surfaces or an octagon with eight side or peripheral surfaces. The actuator can be held on the corresponding side surfaces with low losses. A contour of the polygonal plate with more than eight side or peripheral surfaces is also conceivable.

The provision of several outer peripheral surfaces of the drive element makes it possible to reduce the adhesive surface and thus increase the reliability of the adhesive connection of the drive element when the actuator is heated during operation.

It is particularly advantageous if the ultrasonic actuator or the polygonal plate has only one active generator of acoustic standing waves. This enables the use of a simple single-phase electrical excitation device for electrical excitation of the ultrasonic actuator.

[0031] It can also be advantageous for the ultrasonic actuator or the polygonal plate to have two active generators, through whose simultaneous excitation a planar acoustic standing wave can be generated in it. By influencing the phase angle and the amplitude ratio of the corresponding two excitation voltages, the trajectory of a friction contact point of the drive element can be changed and the movement properties of the part to be driven can thus be influenced.

[0032] It can also be advantageous for the planar acoustic traveling wave to be generated by superimposing two or more than two planar ones Standing waves of the same frequency can be produced. This results in a particularly effective and reliable drive of the element to be driven.

[0033] It can also be advantageous that longitudinal standing waves can be generated in the polygonal plate along its circumference or along one of its diagonals or along a direction that runs perpendicular to the side or circumferential surfaces. In addition, it can be advantageous that a bend in the plane about the axial axis can be stimulated in the polygonal plate. Furthermore, it can be advantageous that further planar standing waves can be excited in the polygonal plate. Such standing waves have a particularly high coupling factor.

It can also be advantageous that the drive element is a disk with a round, triangular, square, square, pentagonal, hexagonal, octagonal or an n-sided polygonal contour. As a result, in the case of an adhesive connection between the drive element and the ultrasonic actuator, the adhesive surface between these two elements is reduced, whereby mechanical stresses can be reduced and the reliability of the adhesive connection can be increased.

[0035] Furthermore, it can be advantageous for the drive element to have recesses in the form of openings or slots, whereby the openings can be round or elongated openings. In addition, it can be advantageous for the drive element to be formed from individual segments. This makes it possible to reduce the mechanical stresses on the contact surface between the drive element and the ultrasonic actuator or the polygonal plate when the ultrasonic actuator heats up or when there are large vibration amplitudes on the ultrasonic actuator, which increases the operational reliability of the motor.

It can be of particular advantage here that the recesses are filled with a sound-absorbing material, whereby parasitic vibrations of the ultrasonic actuator or the polygonal plate are effectively dampened, resulting in a more effective drive via the Frictional contact between the drive element and the element to be driven is achieved.

[0037] In addition, it can be advantageous that an elastic contour element, preferably made of a metallic or a ceramic material, is arranged on the side or peripheral surfaces of the polygonal plate. The use of such an elastic element, which compresses the ultrasonic actuator, increases the strength of the ultrasonic actuator. This makes it possible to apply higher power to the actuator, which results in a higher movement speed of the element to be driven.

It can be advantageous that the element to be driven is designed as a solid or as a hollow threaded rod with at least one longitudinal opening or at least one slot, which preferably runs in the axial direction. This reduces the start and stop times of the ultrasonic motor, as well as its amplitudes of parasitic oscillations.

In the event that the element to be driven is designed as a hollow threaded rod, it can be advantageous if the corresponding cavity in the element to be driven is filled with a sound-absorbing material. This makes it possible to reduce the parasitic vibrations that arise in the element to be driven, thereby improving the engine function.

[0040] In addition, it can be advantageous for the ultrasonic motor to have a pressing device with which the element to be driven is pressed against the drive element and which acts on the element to be driven in a direction that runs longitudinally to the vertical axis of the ultrasonic actuator. This ensures reliable operation of the ultrasonic motor.

It can be advantageous if the pressing device is designed as part of the element to be driven or is arranged in it. This leads to a simplified construction and enables particularly compact dimensions of the ultrasonic motor. [0042] It can also be advantageous if the ultrasonic actuator is held on its outer peripheral surfaces. This makes it possible to achieve a particularly simple and loss-free holder.

[0043] Furthermore, it can be advantageous for the ultrasonic motor to have a fastening device for the ultrasonic actuator or the polygonal plate, the fastening device comprising acoustic resonance elements with the aid of which the ultrasonic actuator can be connected to a base plate or to a motor housing. The acoustic resonance elements can reduce the mechanical losses at the fastening points.

[0044] It may prove advantageous for each of the generators of planar standing waves to have a three-layer structure consisting of an excitation electrode, a common electrode and a piezoelectric material arranged between the two electrodes between them, or a multilayer or multilayer structure in which the electrode layers and the layers of the piezoelectric material are arranged alternately. The multilayer or multilayer structure allows the electrical excitation voltage to be reduced.

Advantages and expediencies of the invention become clearer from the following description of preferred exemplary embodiments based on the figures. Show it:

1: Ultrasonic motor according to the invention with an ultrasonic actuator controlled in a single phase by an electrical excitation device

2a)-e): Representations to explain the functional principle of the ultrasonic motor according to the invention, where representations a) and b) show deformation phases of the polygonal plate or the ultrasonic actuator, and representations c) to e) show trajectories of a surface point of an inner circumferential surface of the ultrasonic actuator with appropriate electrical control

3: Ultrasonic motor according to the invention with an ultrasonic actuator controlled in two phases by an electrical excitation device

4: Ultrasonic motor according to the invention with an ultrasonic actuator controlled in three phases by an electrical excitation device 5: possible embodiments of the polygonal plate or disk of an ultrasonic motor according to the invention

Fig. 6: Ultrasonic actuator of an ultrasonic motor according to the invention with a hexagonal shape or contour and a drive element with a circular contour inserted therein

7 with representations 34 to 40: different embodiments of the drive element of an ultrasonic motor according to the invention

Fig. 8: Ultrasonic actuator of an ultrasonic motor according to the invention with a hexagonal contour and a drive element inserted therein with a hexagonal contour and elastic contour elements

9 with representations 48 to 55: possible embodiments of the element to be driven of an ultrasonic motor according to the invention

Figs. 10, 11: Sectional views to illustrate possible engagement geometries between the element to be driven and the drive element of an ultrasonic motor according to the invention

12: Ultrasonic motor according to the invention with a pressing device acting from the outside on the element to be driven

13: Ultrasonic motor according to the invention with a pressing device arranged within the element to be driven

Figs. 14, 15: Ultrasonic motors according to the invention with different embodiments for holding the ultrasonic actuator

16 with representations 76 to 78: possible embodiments for the drive element of an ultrasonic motor according to the invention

17: Arrangement of the drive element according to illustration 78 of FIG.

16 in an ultrasonic motor according to the invention

18: Ultrasonic motor according to the invention with several ultrasonic actuators

19: Illustration to illustrate the electrical control of the generators of an ultrasonic motor according to the invention

Fig. 20: Embodiment of a generator for generating standing waves in the ultrasonic actuator of an ultrasonic motor according to the invention with a single piezoelectric layer Fig. 21: Embodiment of a generator for generating standing waves in the ultrasonic actuator of an ultrasonic motor according to the invention with a multi-layer structure

22 with representations a) to d): Simulations of the deformations of an ultrasonic actuator with a square contour of an ultrasonic motor according to the invention when exciting different planar acoustic standing waves

23 with representations a) to c): Simulations of the deformations of an ultrasonic actuator with a hexagonal contour of an ultrasonic motor according to the invention when exciting different planar acoustic standing waves

Fig. 24: Illustrations explaining the functional principle of the ultrasonic motor according to the invention according to the Figs. 3 and Fig.4, where representation a) corresponds to a top view, and representation b) corresponds to a side view

25: Electrical circuit of the ultrasonic motor according to the invention according to FIG. 1 for a single-phase excitation [0069] Fig. 26: Electrical circuit of the ultrasonic motor according to the invention according to FIG. 1 or FIG. 27: Electrical circuit of the ultrasonic motor according to the invention according to FIG. 4 for three-phase excitation

1, the ultrasonic motor according to the invention has an ultrasonic actuator 1 and an element 2 to be driven. The ultrasonic actuator 1 in the form of a rectangular disk or plate is made of a piezoelectric ceramic and corresponds to a polygonal plate or disk 4. The polygonal plate 4 has an eccentrically arranged opening or opening 5, on the inner peripheral surface of the opening or the Breakthrough 5 has a thin-walled drive element 6 compared to the diagonal dimensions of the ultrasonic actuator 1. The drive element 6 and the opening 5 have a round shape, although an n-polygonal shape is also conceivable. The polygonal plate 4 is separated by two mutually perpendicular cutting planes P1, P2, which pass through the middle of the opposite outer peripheral or side surfaces 18. The opening 5 is arranged asymmetrically with respect to the cutting plane P1 and symmetrically with respect to the cutting plane P2. It is conceivable that the polygonal plate 4 could also be made of another piezoelectric material, e.g. B. a single crystal material. The inner peripheral surface 7 of the drive element 6 has a thread, not shown, with a thread height q. The element 2 to be driven is designed as a solid or solid threaded rod or threaded rod 9 with a thread 11 on its outer peripheral surface 10, the thread 11 also having a thread height q. The element 2 to be driven is screwed into the drive element 6. The thread on the inner peripheral surface 7 of the drive element 6 and the thread 11 on the outer peripheral surface 10 of the element 2 to be driven form a friction contact.

Furthermore, the polygonal plate or disk 4 of the ultrasonic actuator 1 shown in FIG. 1 has an active generator 13 for a planar standing wave. An active generator for a planar standing wave is to be understood as meaning a generator which is actually electrically excited during operation of the actuator by means of an electrical excitation device 3 and only this active generator generates a planar acoustic standing wave.

The generator 13 is arranged asymmetrically with respect to the cutting planes P1 and P2. A planar standing wave is to be understood as meaning a wave that propagates in the plane of the polygonal plate, the oscillation amplitude of the material particles of the polygonal plate being at least one order of magnitude smaller in the axial direction than in the directions of the plate plane.

To realize a movement of the element 2 to be driven of the ultrasonic motor shown in FIG. 1, only an active generator of acoustic waves 13 is sufficient, although it can also be advantageous that two or more than two active acoustic wave generators 13 are present.

The point 22 indicates a small area on the inner peripheral surface of the polygonal plate 4, which, when the active generator 13 is excited, passes through an elliptical trajectory 23 shown in FIG.

In order to realize a reversible movement 26, 27 of the element 2 to be driven, the ultrasonic motor shown in FIG .

Each of the two generators 13 is connected with its connections 15 and 16 via a changeover switch 25 to the electrical excitation device 3, which consists of an electrical generator 17 for an electrical alternating voltage U1. The alternating electrical voltage generator 17 is intended to electrically excite the active generator 13. Changing the direction of movement 26 or 27 of the element 2 to be driven takes place by switching the electrical excitation device 3 between the two active generators 13 using the switch 25. The single-phase control of the ultrasonic actuator 1 enables a simple electronic switching of the electrical excitation device 3.

2 illustrates in representations a) and b) instantaneous deformations of the polygonal plate at /2 and 3JI/2 of its oscillation period when an active generator 13 is excited, calculated using FEM. The point 22 located on the inner peripheral surface 7 passes through an elliptical Trajectory 23.

In the representations c) and d) of Fig. 2, the polygonal plate 4 of the ultrasonic motor shown in Fig. 1 is illustrated for the realization of a reversible movement of the element 2 to be driven. The first generator 13 (see Fig. 2c)) is connected to the excitation device 3 for a first direction of movement. The elliptical trajectory of the point 22 runs tangentially to the opening 5 and at an angle a to the cutting plane P2. For a second In the direction of movement 26 or 27, the second generator 13 is connected to the excitation device 3, so that the elliptical trajectory changes its inclination mirror-symmetrically with respect to the section plane P2 (Fig. 2d)).

2e) illustrates the polygonal plate 4 of the ultrasonic motor shown in FIG. 1, with the first generator 13 and the second generator 13 being active at the same time. For this purpose, both generators are supplied with two electrical voltages at the same time. The possible trajectories of point 22 are indicated by dashed ellipses. By changing the phase angle between the two control voltages and their voltage amplitudes, it is possible to change the trajectory and thus influence the movement of the element 2 to be driven.

3 and 4, the ultrasonic actuator 1 of an ultrasonic motor according to the invention is designed here as a square (Fig. 3) or hexagonal (Fig. 4) polygonal plate 4 made of a piezoelectric ceramic, which has an opening or a breakthrough 5 , with a thin-walled drive element 6 sitting on the inner peripheral surface of the polygonal plate 4 compared to the diagonal dimensions of the ultrasonic actuator 1. It is conceivable that the polygonal plate 4 could also be made of another piezoelectric material, e.g. B. a single-crystalline material. The drive element here has a round shape, although an n-polygonal shape is also possible.

The polygonal plate 4 of the ultrasonic motor according to Figures 3 and 4 comprises at least one generator 12 for a planar traveling wave, which is formed from two or more than two active generators 13 for planar standing waves. The ultrasonic motor shown in Fig. 3 contains two active generators 13. They are spatially arranged offset from one another by 90°. The generators 13 are part of the polygonal plate 4 or are designed integrally with it, so that no acoustic boundary is formed between them, ie the acoustic waves pass freely and without reflection at the geometric boundary from one generator 13 into an adjacent generator 13. Each of the generators 13 is connected with its connections 15 and 16 to the electrical excitation device 3, which consists of two or more than two electrical generators 17 for alternating electrical voltages U1...Un. The generators 17 are intended for electrically exciting the generators 13 of the planar standing waves. For reasons of clarity, only two generators 17 for the electrical alternating voltages U1 and U2 are shown in FIG. The generators are rotated relative to each other about the vertical axis 14 of the ultrasonic actuator 1 in such a way that the planar standing waves generated by them are shifted by A/4, ie by 90°, relative to one another. For this purpose, the two generators 17 of the electrical excitation device 3 each provide an electrical alternating voltage, the frequency of which essentially corresponds to the resonance frequency of the plane acoustic standing waves generated, the phase of each voltage being shifted by plus 90° or minus 90° relative to one another, and the amplitudes of the electrical voltages are equal. The two-phase control of the generator 12 or the generators 13 enables a relatively simple electronic circuit of the electrical excitation device 3.

The ultrasonic motor shown in FIG. 4 differs from the ultrasonic motor shown in FIG. For reasons of clarity, only three generators 13 are shown in FIG. The generators are rotated relative to each other about the vertical axis 14 of the ultrasonic actuator 1 in such a way that the plane standing waves generated by them are shifted by A/3, ie by 120°, relative to each other. For this purpose, the three generators 17 of the electrical excitation device 3 each provide an electrical alternating voltage, the frequency of which essentially corresponds to the resonance frequency of the plane acoustic standing waves generated, the phase of each voltage being shifted by 120 ° relative to one another and the amplitude of the electrical voltages are equal. The contour of the polygonal plate 4 of the ultrasonic motors according to the invention shown in FIGS. 2 and 3 can also be a triangle, a pentagon or an n-polygon.

5 shows different embodiments of the polygonal plate 4 of an ultrasonic motor according to the invention in illustrations 28 to 33. The polygonal plate has two large main surfaces 19 and at least three outer peripheral or side surface surfaces 18. The polygonal plate can be triangular (see illustration 28), square (see illustration 29), rectangular (see illustration 30), pentagonal (see illustration 31), hexagonal (see illustration 32) or octagonal (see illustration 33). or have a different type of n-sided polygonal contour. The pointed corners of the polygonal plate shown in FIG. 5 can be separated or rounded.

6 shows the ultrasonic actuator 1 in the form of a hexagonal or hexagonal polygonal plate 4 of the ultrasonic motor according to FIG. 4. The drive element 6 with a round contour is inserted into this. P denotes the diameter of the circle C connecting all vertices of the polygonal plate, while S denotes the circumference of the circle C. The thickness of the ultrasonic actuator 1 or the polygonal plate 4 between the main surfaces 19 is h. H denotes the radial distance between the inner circumferential surface 7 of the drive element 6 and the circle C. Furthermore, D denotes the diameter based on the inner circumferential surface 7 of the drive element 6 and L denotes the circumference based on the inner circumferential surface 7 of the drive element 6. The sizes D and L refer each to the corresponding dimension that is present at half the thread height q (see Fig. 10 and Fig. 11). The wall thickness of the drive element 6, i.e. H. the thickness in the radial direction is t.

It can be advantageous to design the ultrasonic actuator 1 or the polygonal plate 4 in such a way that L is equal to or approximately equal to 2 H, where the ratio D to H is equal to p 0.63 or -1.27; - 1.91; -2.54; -3, 18; -3.82; p 4, 45 etc. (generally p (0.63 + n 0.64) with n = natural number). Included p is a coefficient that lies between 0.8 to 1.5 and which depends on the ratio of the modulus of elasticity of the piezoelectric material of the ultrasonic actuator 1 to the modulus of elasticity of the material of the drive element 6. The thickness h of the ultrasonic actuator 1 is chosen so that it is less than H/3. The wall thickness t of the drive element 6 is smaller than H/8. It is particularly advantageous if S is a multiple of H.

The thin-walled drive element 6 is made of a hard, abrasion-resistant material whose hardness and abrasion resistance exceeds the hardness and abrasion resistance of the piezoelectric material of the ultrasonic actuator. Examples of such materials are heat-treated steel, oxide ceramics based on alumina, zirconium oxide, sialon, silicon nitride, metal ceramics based on tungsten carbide and titanium carbide. The thin-walled drive element 6 is directly bonded to the ultrasonic actuator using an organic adhesive (e.g. epoxy resin). The adhesive can contain solid non-organic components such as: B. contain oxide ceramic particles, metal particles or metal ceramic particles. It is also conceivable to realize the drive element 6 with the polygonal plate 4 by a connection that forms during the sintering of the polygonal plate 4. During the sintering process of the piezoelectric material, strong chemical bonds can build up with the material of the drive element 6, which lead to a very strong connection between the ultrasonic actuator 1 or polygonal plate 4 and the drive element 6.

The drive element 6 can be indirectly connected to the ultrasonic actuator via an intermediate element (not shown in FIG. 6). This intermediate element preferably has a thickness k, where k is less than 0.1 H. It is advantageous if the intermediate element consists of a material whose modulus of elasticity and coefficient of thermal expansion correspond approximately to the modulus of elasticity and the coefficient of thermal expansion of the piezoelectric material of the ultrasonic actuator. An example of such a material is a special oxide or metal ceramic. The intermediate element can be made by a cohesive material Connection, realized via a slightly melting glass, can be connected to the polygonal plate 4 of the ultrasonic actuator 1. It is also conceivable to realize a connection between the intermediate element and the polygonal plate 4 of the ultrasonic actuator 1 by a connection that forms during the sintering of the polygonal plate 4. During the sintering process of the piezoelectric material, strong chemical bonds can build up with the material of the intermediate element, which lead to a very strong connection between the ultrasonic actuator and the intermediate element.

7 shows different embodiments for the drive element 6 in illustrations 34 to 40. The drive element 6 is designed as a ring or hollow cylinder with circular outer and inner circumferential surfaces according to illustration 34, while according to illustration 35 it has an outer contour with eight of each other distinguishable surfaces 41 has a hexagonal contour or shape. Through such a multi-surface design of the outer circumference of the drive element, mechanical stresses can be reduced when the drive element is adhesively connected to the polygonal plate, which increases the reliability of this adhesive connection, particularly with large diameters. In representations 36 to 38 of FIG. 7, the drive element has round openings or recesses or openings 42 (representation 36) or elongated openings or openings 43, 44 (representations 37 and 38). In addition, the drive element 6 can also have slots 45 which are not continuous as shown in illustration 39 of FIG. 7. According to illustration 40 of FIG. 7, the slots can also be continuous, so that the drive element 6 consists of individual ring or hollow cylinder segments. It is conceivable that the openings or openings 42, 43, 44 or the slots 45 are filled with a sound-absorbing material.

8 shows an ultrasonic actuator of an ultrasonic motor according to the invention in the form of a polygonal plate 4 having six outer circumferential or side surfaces 18 according to illustration 32 of FIG. 5 or according to FIG. 6, in which a drive element 6 with an eight Having outer peripheral surfaces, ie a hexagonal shape as shown in illustration 35 of FIG. 7 is used. On its outer circumferential or side surfaces 18, the polygonal plate 4 is provided with an elastic contour element 47, which tensions or biases the polygonal plate 4 in the radial direction. The elastic contour element 47 has a thickness d that is less than 0.1 H (see Fig. 6) and is made of steel. The elastic contour element 47 can also be made of oxide ceramic, aluminum oxide or another hard ceramic. It is pressed onto the outer peripheral or side surfaces 18 of the polygonal plate 4. In addition, it is also conceivable to shrink the elastic contour element 47 onto the outer circumferential surfaces 18 of the polygonal plate or to stick it onto them using an organic adhesive (e.g. epoxy resin).

9 shows different embodiments for an element 2 to be driven of an ultrasonic motor according to the invention in illustrations 48 to 55. According to representation 48 of Fig. 9, the element to be driven is designed as a fully threaded rod made of a hard and abrasion-resistant material (e.g. heat-treated steel, oxide or metal ceramic). In addition, as shown in FIGS. 49-52 and 55 of FIG. 9, it is possible to design the element to be driven as a hollow threaded rod, with the corresponding inner opening or cavity 57 having a round shape. However, other geometries of the inner opening are also conceivable (e.g. a polygonal shape). A rod 58 made of a sound-absorbing material can be inserted into the cavity 57 of the hollow threaded rod 2 as shown in illustration 50 of FIG. 9. This rod 58 is made of an elastic material such as. B. Rubber. The elastic material can be filled with hard particles such as B. be filled with metal particles. In addition, it is also conceivable that the rod 58 is made of a viscoelastic material, e.g. B. a thermoplastic material, the viscoelastic material containing particles, e.g. B. can be filled with metal and / or rubber particles. Furthermore, the rod 58 can also be made of a hard porous material, such as. B. made of porous oxide ceramic, the pores of which have a filled with viscous material. A variety of other materials or material mixtures with a high sound absorption factor for the rod 58 are conceivable. The rod 58 can, for example, also be made of a hard material such as steel, oxide ceramic, metal ceramic, with a layer of sound-absorbing material (e.g. rubber, epoxy resin or similar) being arranged between the rod 58 and the element 2 to be driven.

9, the rod 58, like the element 2 to be driven, is designed as a hollow rod, and the rod 58 has an axially arranged opening 60 in which a further sound-absorbing rod 61 is located, between the rod 58 and the sound-absorbing rod 61 a layer 59 of a sound-absorbing material is arranged. According to the representations 52 and 55 of FIG. 9, the element to be driven, which is designed as a hollow threaded rod, can have 2 longitudinal openings 62 or longitudinal slots 63. According to representations 53 and 54 of FIG. 9, the element 2 to be driven, which is designed as a fully threaded rod, can have one or more longitudinal slots 63.

10 shows a possible thread engagement between a drive element 6 and an element 2 to be driven of an ultrasonic motor according to the invention. Here, the thread 8 provided on the drive element 6 and the thread 11 provided on the element 2 to be driven have an isosceles triangular shape. The thread pitch can be 0.1mm to a few mm per thread, while the thread height is q.

11 shows a further possible thread engagement between a drive element 6 and an element 2 to be driven of an ultrasonic motor according to the invention. Both threads 8, 11 have a non-isosceles triangular shape. In principle, by choosing a suitable thread shape, it is possible to increase the force developed by the ultrasonic motor. To increase strength and abrasion resistance, the surface of threads 8 and 11 be provided with a solid, abrasion-resistant material layer. For example, layers made of CrN, CrCN, (Cr, W)N, (Cr, AI)N, NbN-CrN, TiN, TiCN, (Ti, AI)N or V2O5 are suitable for this.

12, the element 2 to be driven of an ultrasonic motor according to the invention is pressed against the drive element 6 with the aid of a pressing device 64, having a leaf spring 65. In a manner not shown, the element 2 to be driven can also be pressed against the drive element 6 with the aid of a helical spring, which acts on the element 2 to be driven along the vertical axis 14 of the ultrasonic actuator or the polygonal plate 1. In the construction shown in FIG. 12, the ultrasonic actuator 1 or the polygonal plate 4 is supported and held by an elastic ring 66 located on a motor housing 67. Here, the elastic ring 66 supports the ultrasonic actuator 1 at the points of minimum vibration speeds of the large main surfaces 19, whereby the mechanical losses in the elastic ring 66 are reduced. The elastic ring 66 is made of rubber, but can also be made of polyurethane or Teflon.

13 shows a further embodiment of an ultrasonic motor according to the invention. Here, the element 2 to be driven is slotted and has correspondingly elastically deflectable legs 69. A shaped spring 68 is arranged in the cavity 57 of the element 2 to be driven, which acts on the legs 69 of the element 2 to be driven and thus presses it against the drive element 6. 13, the ultrasonic actuator 1 or the polygonal plate 4 is held by means of the two annular supports 70, which support it in the points of minimum vibration speeds of the large main surfaces 19, which results in a reduction in the mechanical losses in the supports 70. The supports 70 are made of a hard and heat-resistant rubber. They can also be made of Teflon or another heat-resistant polymer material. 14 illustrates a further possible embodiment of an ultrasonic motor according to the invention, which here has a hexagonal ultrasonic actuator 1 or polygonal plate 4 and in which a housing 67 consists of two parts 71.

15, the ultrasonic motor according to the invention shown there has an ultrasonic actuator 1 or a polygonal plate 4 with a hexagonal contour, which is held on its outer peripheral or side surfaces 18 via a holder 72. For this purpose, the holder 72 has a thin hexagonal holding element 73 into which the ultrasonic actuator 1 is pressed or glued. To reduce mechanical losses, the holder 72 has projections or acoustic resonance elements 74, with the help of which the holding element 73 is connected to a base plate 75. By attaching the ultrasonic actuator 1 or the polygonal plate to its outer peripheral surfaces 18 with the aid of the holding element 73 with the resonance elements 74, the mechanical rigidity of the ultrasonic motor increases.

According to representations 76 and 77 of FIG. 16, the drive element 6 has projections or acoustic resonance elements 74. According to illustration 78 of FIG. 16, the projections or resonance elements 74 of the drive element 6 are connected to the base plate 75. Fastening the ultrasonic actuator 1 via the drive element 6 with the help of the projections 74 also increases the rigidity of the ultrasonic motor significantly. The design of the projections 74 as acoustic resonance elements, in which one of the overtones coincides with the resonance frequency fO, leads to a reduction in mechanical losses.

17 shows an exploded view of an ultrasonic motor according to the invention, in which a square-shaped ultrasonic actuator 1 is combined with a drive element 6 as shown in illustration 78 of FIG. 16, the drive element 6 having projections or resonance elements 74, which in turn are connected to the base plate 75 are connected.

18, the ultrasonic motor according to the invention shown there has several ultrasonic actuators 1 or polygonal plates 4 on. The four ultrasonic actuators 1 or polygonal plates 4 are connected to one another via the resonance elements 74, each of the resonance elements 74 in turn being connected to the drive element 6. It is conceivable, instead of the four ultrasonic actuators 1 shown here, to use only two or three, or even more than four ultrasonic actuators 1 or polygonal plates 4 for the ultrasonic motor according to the invention.

19 shows a schematic top view of an ultrasonic actuator 1 or a polygonal plate 4 of an ultrasonic motor according to the invention with an n-polygonal contour for the arrangement of the generators 12 for the planar traveling wave and the active standing wave generators 13 for a planar standing wave. Here, the generators 12 - relative to the vertical axis 14 - are relative to each other by the wavelength A, i.e. H. shifted by the angle 2TT. To generate a traveling wave in each of the generators 12 with the aid of two standing waves, the standing wave generators 13 must be shifted relative to one another - based on the vertical axis 14 of the ultrasonic actuator 1 - by the angle A/4 or TT/2. To generate a traveling wave with a number of standing wave generators n>3, the standing wave generators 13 in each of the generators 12 must be shifted relative to one another - based on the vertical axis 14 of the ultrasonic actuator 1 - by the angle A/n or 2TT/n. In this case, the traveling and standing waves they generate are also shifted from one another by the angle A/n or 2TT/n.

In each generator for a planar traveling wave or in each traveling wave generator 12, the active generators for a planar standing wave or the standing wave generators 13 of one and the same standing wave can be in phase or out of phase with one another. The electrical alternating voltages U1 to Un generated by the generators 17, not shown in FIG. have a trapezoidal shape or any other shape. It is advantageous if the amplitudes of these voltages are the same. The phases of these voltages U1 to lln are preferably around the angle +/-90 ⁰ (TT/2) or around the angle +/-120 ⁰ (2TT/3)) or another angle 2TT/n, which results from the number n is determined, which indicates the number of active standing wave generators 13 of which each traveling wave generator 12 consists, shifted from one another.

20 shows a possible embodiment of a generator 13 for a planar standing wave or a standing wave generator 13. This has a three-layer structure which consists of an excitation electrode 79, a general electrode 80 and a polarized piezoelectric ceramic layer 81 between them. The arrows shown in FIG. 20 indicate the direction of polarization of the piezoceramic layer 81.

21, the generator 13 has a multilayer structure with alternately arranged layers of the excitation electrode 79, the general electrode 80 and the piezoceramic 81 between them. The arrows in Fig. 21 indicate the polarization direction of the piezoceramic layers 81, whereby the polarization directions of adjacent generators 13 can be directed in the same direction or differently. With a multilayer structure of the generator 13 or the generators 13, the voltage supply to the ultrasonic motor according to the invention can take place with a lower voltage.

22 uses illustrations a) to d) to illustrate the formation of different waves in a polygonal plate of an ultrasonic motor according to the invention that is excited with the aid of an active generator. Illustrations a) to d) show the maximum deformations of the polygonal plate calculated using FEM with the corresponding wave formation. There can be a standing bending wave of the polygonal plate in its plane (Fig. 20a)), a longitudinal standing wave in the direction of the circumference of the polygonal plate (Fig. 20b)), a longitudinal wave in the direction of the diagonal of the polygonal plate (Fig. 20c)) or a longitudinal wave in the direction perpendicular to the side surfaces of the polygonal plate (Fig. 20d)). The Excitation of other planar modes is possible, as is the excitation of the above-mentioned standing waves of a higher order.

23 uses corresponding FEM calculations to illustrate possible standing waves or the resulting maximum deformations in the polygonal plate 4 of the ultrasonic motor shown in FIG plane (Fig. 21a)), a longitudinal standing wave in the direction of the circumference of the polygonal plate (Fig. 21b)), a longitudinal wave in the direction of the diagonal of the polygonal plate (Fig. 21c)), or a longitudinal wave in the direction perpendicular to side surfaces of the polygonal plate ( Fig. 21 d)) or excited. The excitation of other planar modes as well as the excitation of the above-mentioned standing waves of a higher order are also possible.

24 serves to explain the drive principle of the ultrasonic motors according to the invention shown in FIGS. 3 and 4. Here, in illustration a), the polygonal plate 4, into which the drive element 6 is inserted and connected to it, and the element 2 to be driven, which is in threaded engagement with the drive element 6, is shown in plan view. The points 82 lie on the inner peripheral surface 7 or the thread 8 of the drive element 6. When a traveling wave propagating in the direction of the arrow 83 is excited (rotating) in the ultrasonic actuator 1 or in the polygonal plate 4, the points 82 move on the closed round ones Movement trajectories 84. The movement trajectories 84 can also be elliptical, for example. The arrow 85 illustrates the direction of movement of the material points. The frictional contact between the drive element 6 and the element 2 to be driven, ie the thread contact or thread engagement, causes the element 2 to be driven to rotate in the direction indicated by arrow 26. The representation b) is the corresponding side view to the representation a) of Fig. 24. The arrow 27 indicates the direction of the longitudinal movement of the element 2 to be driven, which results from the rotation of the same. 25 illustrates a possible electrical connection of the ultrasonic actuator 1 or the polygonal plate 4 of the ultrasonic motor according to the invention according to FIG a movement of the element 2 to be driven via the changeover switch 25 to either the first or the second active standing wave generator 13. The frequency of the generator 17 corresponds to the frequency of the longitudinal standing wave to be excited in the polygonal plate 4 in the direction of its diagonal. The change in the direction of movement of the element 2 to be driven takes place by actuating the switch 25.

26 illustrates a further possible electrical connection of the ultrasonic actuator in the form of a polygonal plate 4 of the ultrasonic motor according to the invention according to FIG .to generate a movement of the element 2 to be driven via the changeover switch 25 to the first and second active generator for a standing wave 13. The frequencies of the generators 17 are equal to the frequency of the longitudinal standing wave to be excited in the polygonal plate 4 in the direction of its diagonal. The phase shift between the voltages U1, U2 and their amplitudes can take on any values. The change in the direction of movement of the element 2 to be driven takes place by actuating the switch 25. It is also possible to reverse the direction of movement by changing the phase shift between the voltages U1, U2 by ±90°.

It is also possible to connect the ultrasonic motor according to the invention shown in FIG. 3 to the electrical excitation device 3 using the circuit shown in FIG. 2) is and their amplitudes are equal. 27 illustrates a possible electrical connection of the ultrasonic actuator in the form of a polygonal plate 4 of the ultrasonic motor according to the invention according to FIG Generator 17 for exciting the polygonal plate 4 or for generating a movement of the element 2 to be driven via the changeover switch 25 to the three active standing wave generators 13. The frequencies of the generators 17 are equal to the frequency of the planar standing waves to be excited in the polygonal plate 4, shown in Fig. 23. The phase shift between the voltages U1, U2 for generating a traveling wave is 120 ° (2K/3) and their amplitudes are the same . The change in the direction of movement of the element 2 to be driven takes place by actuating the switch 25. It is also possible to reverse the direction of movement by changing the phase shift between the voltages U1, U2 by ±120°.

The creation of standing waves or eigenmodes in various geometric bodies is defined by boundary conditions. Features such as angles, surfaces, openings, etc. represent the most important boundary conditions for the appearance (ie the eigenform) of the standing waves (ie the modes) that occur in a geometric body. Therefore, the eigenmodes belonging to a geometric body are specific and characteristic of it. Planar eigenmodes of plates or disks represent a subset of standing waves in which the oscillation of the material points of the body occurs mainly in the plane of the plate. The oscillation amplitudes in a direction perpendicular to the large plate sides are at least an order of magnitude smaller than in the other two directions perpendicular to them and do not arise directly due to the wave process, but are caused by transverse contractions as a side effect of the waves propagating within the plane of the plate. Planar eigenmodes have a high coupling factor. Their piezoelectric excitation is very efficient, i.e. it A high proportion of the electrical energy is converted into the mechanical energy of the vibrations.

In the embodiment of the ultrasonic motor according to the invention according to FIG. 1, the piezoelectric ultrasonic actuator 1 designed as a polygonal plate 4 has two generators 13 for generating standing waves. The electrical excitation device 3 generates an alternating electrical voltage with a sine, triangular, rectangular or any other shape, the main harmonic of which corresponds to the resonance frequency or close to the resonance frequency of the first or second mode of the acoustic longitudinal standing wave, which is longitudinal to the diagonal 24 of the polygonal plate 4 spreads, lies. When connecting the excitation electrodes 20 and the reference electrode 21 of a generator 13 to the electrical excitation device 3 (see Figures 1 and 26), an acoustic longitudinal standing wave is generated in the polygonal plate 4, which propagates along its diagonal 20. The ultrasonic actuator 1 or the polygonal plate 4 begins to vibrate in the form shown in Figures 2a) and 2b). The point 22 lying below the intersection of the diagonals 24 on the inner peripheral surface of the polygonal plate 4 moves on an elliptical movement path 22 inclined at an angle a to the plane P2 (see Figures 2c) and 2d)). Since the drive element 6 is thin-walled and is acoustically rigidly connected to the polygonal plate 4, the nearby points on the thread surface also move along a tangential elliptical path. Because of the eccentric arrangement of the opening 5, this movement of the drive element 6 creates a friction force which gives the element 2 to be driven a torque.

An active standing wave generator 13 is sufficient to generate the movement of the element 2 to be driven. In order to realize a reversible movement of the element 2 to be driven, the ultrasonic motor shown in FIG. 1 has two generators 13 of acoustic standing waves, with only one of them being the active generator in operation for the respective direction of movement. Each generator 13 is connected with its connections 15 and 16 via the changeover switch 25 to the electrical excitation device 3, which includes an electrical generator 17 for the electrical alternating voltage U1. The generator 17 is intended to electrically excite the active generator 13. The change in the direction of movement of the element 2 to be driven takes place by switching the electrical excitation on the part of the generator 17 between the two active generators 13 using the switch 25. By operating the changeover switch 25, it is possible to apply the electrical voltage provided by the electrical excitation device 3 from the generator 17 to the first or second generator 13 and vice versa. By switching, the angle of inclination a of the movement path 23 of the drive element 6 is reversed. This leads to a reversal of direction 26, 27 of the element 2 to be driven. Single-phase control of the ultrasonic actuator 1 enables a particularly simple electronic circuit of the electrical excitation device 3.

However, it can also be advantageous to excite the ultrasonic motor according to the invention by means of a two-phase excitation device with any desired phase shift and different amplitudes, as is somewhat shown in FIG. Both standing wave generators 13 are active at the same time. The direction of movement of the element 2 to be driven is reversed by exchanging the excitation between the two active generators 13 using the switch 25. Furthermore, it is possible to influence the elliptical trajectory 23 of the contact point 22 in the frictional contact by changing the phase angle and the amplitudes of the electrical voltages U1, U2 and thus change the speed and torque of the ultrasonic motor. This two-phase excitation makes it possible to significantly increase the linearity of the movement speed of the element to be driven at low speeds of less than 1 micrometer/s.

The advantageous embodiments for an ultrasonic motor according to the invention shown in Figures 3 and 4 work as follows: on An electrical voltage U1, U2, lln is applied to each of the generators 13 of the planar standing wave by the generator 17. This voltage excites the corresponding generator 13, which in turn generates a planar standing wave of the corresponding order in the polygonal plate 4, in which the maximum of the oscillation amplitude of the polygonal plate 4 is located in the radial direction on the threaded surface 7 of the drive element 6 or adjacent to the threaded surface 7. The representations a) to d) of Figures 22 and 23 show the deformation images of the polygonal plate 4 when such a wave is generated in this embodiment variant of the ultrasonic motor. The shape of the deformation of the standing wave used is determined by the boundary conditions of the polygonal plate 4, ie by its outer surfaces, angles and its inner opening 5. The wave generated represents a planar standing wave in which the oscillation amplitude of the polygonal plate 4 in the axial direction is more than an order of magnitude smaller than the oscillation amplitude in the directions perpendicular to it, ie in the directions parallel to the large main sides. The vibrations of the material points mainly take place in the plane of the polygonal plate 4. When all generators 13, of which the generator 12 or the generators 12 consist or consist, are excited at the same time, a plane traveling wave propagates in the polygonal plate 4.

In practice, this means that depending on the sign of the phase shift between the standing waves, the deformation images of the polygonal plate 1 (see illustrations a) to d) of Figures 22 and 23) begin to rotate clockwise or counterclockwise.

When a planar traveling wave propagates in the direction indicated by arrow 83 according to FIG. 24 within the polygonal plate 4, the points 82 of the thread surface 7 of the thread 8 move on circular or elliptical movement paths 84 in the direction indicated by arrow 85 . Since the excited wave represents a planar wave, all points lying on top of each other have 82 (in the axial direction) along the inner circumferential surface 7 of the drive element 6 the same diameter of the movement paths 84.

Since the thread surface 7 of the drive element 6 is in contact with the thread surface 10 of the threaded rod 9 and these surfaces are pressed together, the circular movement of the points 82 leads to a rotation in the direction indicated by arrow 86 of the element 2 to be driven in the form of Threaded rod 9.

[00124] The peculiarity of the movement paths 84 of the points 82 significantly increases the efficiency of the frictional contact, since the maximum force with which the polygonal plate acts on the element 2 to be driven is determined by the maximum frictional force at rest between the surfaces 7 and 10. The rotation of the element 2 to be driven in the drive element 6 in the direction indicated by arrow 26 leads to its axial direction indicated by arrow 27 in FIG. 24, i.e. to a longitudinal displacement or longitudinal movement.

The change in the direction of propagation of the traveling wave leads to a change in the direction of rotation of the element 2 to be driven and to a change in the axial direction, i.e. the longitudinal displacement.

Since the drive element 6 is thin-walled, that is, its thickness t is significantly smaller than the width of the polygonal plate 4 in the radial direction, the vibration of the ultrasonic actuator 1 is only slightly disturbed or changed by the drive element connected to it. Therefore, the electromechanical coupling coefficient of the ultrasonic actuator is determined by the electromechanical coupling coefficient of the polygonal plate 4. This means that the electromechanical coupling coefficient of the ultrasonic actuator 1 is maximized in the ultrasonic motor according to the invention. This significantly increases its vibration speed and thus the maximum possible load on the ultrasonic actuator 1, which also results in an increased holding force of the ultrasonic motor according to the invention. [00127] List of reference symbols

1 ultrasonic actuator

2 element to be driven

3 electrical excitation device

4 polygonal plate

5 breakthrough or opening (of the polygonal plate 4)

6 drive element

7 inner circumferential surface (of the drive element 6)

8 threads (the inner peripheral surface 7)

9 threaded rod

10 outer peripheral surface (of the threaded rod 9)

11 threads (the threaded rod 9)

12 Generator (a planar acoustic traveling wave)

13 active generator (a planar acoustic standing wave)

14 vertical axis (of the polygonal plate 4)

15, 16 connection (of the generator 13)

17 generator of an electrical alternating voltage

18 side surface (of the polygonal plate 4)

19 Main surface (of the polygonal plate 4)

20 excitation electrode (of the generator 13)

21 general or reference electrode

22 point (on the inner peripheral surface of the polygonal plate 4)

23 elliptical trajectory (of point 22)

24 diagonal (of polygonal plate 4)

25 electrical changeover switch (for the direction of movement of the element 2 to be driven)

26 Direction of rotation (of the element 2 to be driven)

27 feed direction (of the element 2 to be driven)

41 peripheral surface (of the drive element 6)

42-44 openings or breakthroughs (of the drive element 6)

45 slot (of the drive element 6)

46 segment (of the drive element 6)

47 elastic contour element Cavity (of the element 2 to be driven), 61 sound-absorbing rod

Layer of sound-absorbing material

Fixing opening (of the sound-absorbing rod 61)

Longitudinal opening (of the element 2 to be driven)

Slot (of the element to be driven 2)

Pressing device

Leaf spring elastic ring

Motor housing

Shaped spring, elastically deflectable leg (of the one to be driven

elements 2)

support

Part (of the motor housing 67)

holder

Holding element (of the holder 72)

Resonance element

base plate

Excitation electrode (of the generator 13) common electrode (of the generator 13) piezoceramic layer

Point (on the inner peripheral surface 7)

Arrow (to indicate the direction of propagation of the plane traveling wave)

Trajectory (of point 82)

Arrow (to indicate the direction of movement of point 82 on trajectory 84)

Arrow (to indicate the direction of rotation of the element to be driven 2)

Arrow (to mark the longitudinal direction of the element to be driven 2)

Claims

Expectations

Claim 1 Ultrasonic motor, comprising at least one piezoelectric ultrasonic actuator (1) with at least one generator (12) for generating a planar acoustic traveling wave, an element (2) to be driven with an external thread (11) and a drive element (6) with a thread ( 8) provided inner circumferential surface (7) and an outer circumferential surface, the drive element being inserted into the ultrasonic actuator (1), so that it surrounds the drive element (6) via an inner circumferential surface on its outer circumferential surface, the element to be driven (2) and the drive element (6) are in threaded engagement and the planar acoustic traveling wave can be transferred from the ultrasonic actuator (1) to the drive element (6), so that a rotation of the element (2) to be driven can be caused, and the ultrasonic actuator (1) has at least one active generator ( 13) for generating a planar acoustic standing wave, the maximum of the vibration speed of which is present in the area of the inner peripheral surface of the ultrasonic actuator (1), characterized in that the ultrasonic actuator (1) has the shape of a polygonal plate (4) with two large main surfaces (19) and has at least three smaller side surfaces (18) connecting the two main surfaces (19).

Claim 2 Ultrasonic motor according to claim 1, characterized in that the contour of the polygonal plate (4) has the shape of a triangle or a square or a rectangle or a pentagon or a hexagon or an octagon.

Claim 3 Ultrasonic motor according to claim 1 or 2, characterized in that the planar acoustic standing wave can be generated by simultaneously controlling two active generators (13) of the ultrasonic actuator.

Claim 4 Ultrasonic motor according to one of the preceding claims, characterized in that the planar acoustic traveling wave can be generated by superimposing at least two planar acoustic standing waves of the same frequency.

Claim 5 Ultrasonic motor according to one of the preceding claims, characterized in that in the polygonal plate (4) longitudinal Standing waves can be excited along their circumference or along one of their diagonals or along a direction perpendicular to one of their side surfaces.

Claim 6 Ultrasonic motor according to one of the preceding claims, characterized in that the polygonal plate (4) can be excited by longitudinal standing waves in such a way that a bend in the plane of the polygonal plate about the axial axis results.

Claim 7 Ultrasonic motor according to one of the preceding claims, characterized in that the drive element (6) has the shape of a ring or has a ring-like shape, the contour of which corresponds to an n-sided polygon with n>2, where n corresponds to a natural number.

Claim 8 Ultrasonic motor according to one of the preceding claims, characterized in that the drive element (6) has recesses in the form of openings (36, 37, 38) or slots (39).

Claim 9 Ultrasonic motor according to claim 8, characterized in that the recesses are filled with a sound-absorbing material.

Claim 10 Ultrasonic motor according to one of the preceding claims, characterized in that the drive element (6) is formed from individual segments (40).

Claim 11 Ultrasonic motor according to one of the preceding claims, characterized in that an elastic contour element is arranged on the side surfaces (18) of the polygonal plate (4).

Claim 12 Ultrasonic motor according to one of the preceding claims, characterized in that the element (2) to be driven is designed as a threaded rod which has at least one longitudinal opening (62) or at least one slot (63).

Claim 13 Ultrasonic motor according to claim 12, characterized in that the at least one longitudinal opening (62) or the at least one slot (63) runs parallel to the longitudinal axis of the threaded rod.

Claim 14 Ultrasonic motor according to claim 12, characterized in that the threaded rod is hollow and the corresponding cavity (57) is filled with a sound-absorbing material. Claim 15 Ultrasonic motor according to one of the preceding claims, characterized in that it has a pressing device (64) with which the element to be driven (2) is pressed against the drive element (6) and which acts on the element to be driven (2) in one direction , which runs along a vertical axis of the polygonal plate (4).

Claim 16 Ultrasonic motor according to claim 15, characterized in that the pressing device (64) is part of the element (2) to be driven or is arranged on it.

Claim 17 Ultrasonic motor according to one of the preceding claims, characterized in that the polygonal plate (4) is designed to be held via its side surfaces (18).

Claim 18 Ultrasonic motor according to one of the preceding claims, characterized in that the element (6) to be driven has at least one acoustic resonance element (74) which serves to hold the polygonal plate (4).

Claim 19 Ultrasonic motor according to one of claims 1 to 17, characterized in that it has a holder (72) with a holding element (73) for the polygonal plate (4), the holder (72) having at least one acoustic resonance element (74), through which the polygonal plate (4) is connected to a base plate (75) or to a motor housing (67).

Claim 20 Ultrasonic motor according to one of the preceding claims, characterized in that the at least one active generator for generating a planar acoustic standing wave (13) either has a three-layer structure with an excitation electrode (79), a common electrode (80) and a common electrode between the excitation electrode and the common one Electrode arranged piezoelectric material, or has a multilayer structure, in which layers of excitation electrodes, general electrodes and layers of piezoelectric material arranged between them are arranged alternately.