WO2021164799A1

WO2021164799A1 - Piezoelectric ultrasonic motor

Info

Publication number: WO2021164799A1
Application number: PCT/DE2020/100110
Authority: WO
Inventors: Alexej Wischnewski; Bülent Delibas; Maxim WISCHNEWSKI
Original assignee: Physik Instrumente (Pi) Gmbh & Co. Kg
Priority date: 2020-02-18
Filing date: 2020-02-18
Publication date: 2021-08-26

Abstract

The invention relates to an ultrasonic motor comprising: an ultrasonic actuator (1) in the form of a rectangular piezoelectric plate (2) having two main faces (12, 13), two side faces (14), two end faces (15) and generators (G1, G2, G3, G4) for acoustic standing waves, which generators are arranged in two or four regions of the piezoelectric plate, the piezoelectric plate being divided by one or three transverse planes running perpendicularly to the side faces of said plate and parallel to the end faces of said plate; at least one driven element (6); and an electric control device (27), at least one friction element (3) being arranged on the ultrasonic actuator (1) and being pressed against the at least one driven element (6); and also an electric control device. According to the invention, the generators (G1, G2, G3, G4) of the acoustic standing waves are at the same time generators of static rotary deformations (torsional deformations) or static longitudinal rotary deformations (longitudinal torsional deformations) or static longitudinal deformations of the region of the piezoelectric plate that is arranged below the friction element (3) between two adjacent generators, the static deformations occurring substantially in the plane arranged parallel to the main faces (12, 13) of the piezoelectric plate (2).

Description

description

Piezoelectric ultrasonic motor

The invention relates to a piezoelectric ultrasonic motor according to claim 1.

Ultrasonic motors can be used, for example, as a drive in tables for fine positioning for the semiconductor industry, in laser systems, in lenses for optical systems or in medical technology, where high adjusting or positioning speeds, high resolution and high holding forces of the driven elements are required .

Generic ultrasonic motors are known from the publications DE 102016 110771 B3, DE 102013 110356 A1, EP 1 747594 B1 and US 7598656 B2.

In these ultrasonic motors, acoustic standing waves are excited with the aid of appropriate generators to generate the movement of the friction element. The generators include an exciter electrode arranged over the full area on one of the main surfaces of the piezoelectric actuator plate and a full-area common electrode arranged on the other main surface of the piezoelectric actuator plate. The polarization direction of the piezoceramic of these generators runs from one main surface to the other main surface of the actuator plate.

The acoustic standing waves are excited in the actuator plate using the d31 charge constant.

A certain disadvantage of these ultrasonic motors is their resolution t, which is limited by the minimum step length. The minimum step length of ultrasonic motors is determined by the vibration properties of its vibration system, i.e. the mechanical quality of the actuator. In practice, the mechanical quality of an actuator under load ranges between 10 and 100 units. Such a quality limits the minimum stride length to 10 to 100 nm.

For specific applications, a resolution of 10 to 100 nm, as is achieved for currently known ultrasonic motors, is not sufficient. The range of application of previously known ultrasonic motors is therefore limited.

According to DE 102008012992 A, ultrasonic motors can also be equipped with static multilayer actuators to increase the resolution. This enables resolutions between 0.5 and 5 nm with a simultaneous reduction in the electrical voltage required for operation. However, multi-layer actuators have high-temperature-resistant electrodes that are absolutely necessary for the manufacturing process using sintering. These electrodes are made of expensive materials such as palladium, which makes the production of multi-layer actuators much more expensive. Furthermore, the material strength of sintered multilayer actuators is much lower than that of monolithic actuators due to the presence of internal electrodes. This is why multi-layer actuators can only be operated with lower power compared to monolithic actuators in ultrasonic mode.

From DE 102017 110081 A1 an ultrasonic motor is known in which the generator of acoustic standing waves is at the same time a generator of static longitudinal expansion. Such an actuator is able to achieve step sizes of less than 1 nm in static operation. At the same time, step sizes in dynamic operation are a few micrometers. The implementation of step sizes between a nanometer and a micrometer is not possible, because covering the mentioned step size range required a considerable increase in the electrical control voltage of the actuator. Such an increase in voltage would lead to voltage breakdowns occurring between the electrodes and the operation of the motor would become unreliable.

The object of the invention is therefore to provide a

Ultrasonic motor in which the step size operating range is expanded by overlapping static and dynamic modes. Another object of the invention is to reduce the required static electrical drive voltage of the motor as well as increasing the reliability of its operation by preventing the electrical voltage breakdown between the electrodes.

This object is achieved by an ultrasonic motor according to claim 1. The subsequent subclaims represent at least useful developments.

The ultrasonic motor according to the invention consisting of a

Ultrasonic actuator with a rectangular piezoelectric plate with generators for acoustic standing waves includes generators of acoustic standing waves, which are also generators of static torsional deformations or torsional deformations or static longitudinal torsional deformations or longitudinal torsional deformations or static longitudinal deformations of the area of the piezoelectric plate. The generators are arranged below the friction elements between two adjacent generators. The static torsional deformations generated by the generators using the d33 charge constant mainly take place in the plane parallel to the main surfaces of the piezoelectric plate. The twisting deformations that arise in the area of the friction element of the actuator plate lead to a tilting of the friction element and thereby enable a far greater advance of the driven element compared to longitudinal expansion with the same electrical control voltage.

Fig. 1 shows an embodiment of the invention

Ultrasonic motor. The ultrasonic motor consists of the ultrasonic actuator 1 in the form of a rectangular piezoelectric plate 2 which has a friction element 3 that is pressed against the friction layer 5 of the driven element 6 by means of the spring 4.

The piezoelectric plate 2 has two generators G1, G2 for the acoustic standing waves and the static torsional deformations or torsional deformations or static longitudinal rotary deformations or longitudinal torsional deformations or static longitudinal deformations. The driven element 6 is designed as a longitudinally displaceable body 7 in the form of a rod which is arranged in the housing 9 and mounted by means of the bearing 8. The arrows with the index V illustrate the directions of movement of the driven element 6.

It is conceivable that the displaceable body 7 is also designed as a plate, table or in some other similar form. The actuator 1 is held in the housing 9 with the aid of sound-absorbing stops 10.

Fig. 2 shows a further embodiment of the invention

Ultrasonic motor, in which the driven element 6 is designed as a rotating or rotating body 11 in the form of a ring. The rotating or rotating body 11 can, however, also be designed as a disk or a partial disk, as a partial ring, as a cylinder or partial cylinder, or as a ball or partial sphere.

3 and 4 show two embodiments of the invention

Ultrasonic motor in which the piezoelectric plate 2 of the actuator 1 has four generators G1, G2, G3, G4 for acoustic standing waves and the static torsional deformations or torsional deformations or static longitudinal rotary deformations or longitudinal torsional deformations or static longitudinal deformations.

5 shows an embodiment of the rectangular piezoelectric plate 2 of the actuator 1 of an ultrasonic motor according to the invention. The plate 2 consists entirely of piezoelectric ceramic. It has two main surfaces 12, 13, two side surfaces 14 and two end surfaces 15. The plate 2 has the length L, the width B and the thickness D.

The piezoelectric plate 2 is divided by the virtual transverse plane S into the two equal parts T1 and T2, in which the generators G1 and G2 are arranged. The plane S runs perpendicular to the main surfaces 12, 13, perpendicular to the side surfaces 14 and parallel to the end surfaces 15. The dotted line 16 in FIG. 5 represents the intersection of the plane S with the surfaces 12, 13 and 14.

In this embodiment, the ratio of the length L to the width B of the plate 2 (ie L / B) can be in the range of 2 to 3. With a given Length L determines the ratio L / B the optimal working frequency Fa for the ultrasonic motor according to the invention. The thickness of the piezoelectric plate 2 is preferably smaller than its width B.

Figures 17 and 18 of FIG. 6 show two different ones

Embodiments of the actuator 1 with two generators G1, G2 according to FIG. 5. The first embodiment according to FIG. The second embodiment according to FIG. 18 comprises two friction elements 3, which are each arranged in the central area of the respective side surface 14 of the piezoelectric plate 2 or in the area of the transverse plane S and thus opposite one another. In other words, the generators G1 and G2 are arranged below the friction element 3 and the friction elements 3, respectively.

7 shows a second embodiment of the rectangular piezoelectric plate 2 of the actuator 1 of an ultrasonic motor according to the invention. In this embodiment, the piezoelectric plate 2 is divided by the three virtual transverse planes S into four equal parts T1, T2, T3 and T4, in which the generators G1, G2, G3 and G4 are arranged accordingly. The transverse planes S run perpendicular to the main surfaces 12, 13, perpendicular to the side surfaces 14 and parallel to the end faces 15. The dotted lines 16 in FIGS.

In this second embodiment of the piezoelectric plate 2, the ratio of length L to width B (ie L / B) is in the range from 4 to 6. Here, too, it is advantageous if the thickness of the piezoelectric plate 2 is smaller than its width Are you.

Figures 19 and 20 of Fig. 8 show two embodiments of the actuator 1 with four generators G1, G2, G3 and G4 according to FIG. 7. The first embodiment according to Figure 19 comprises a friction element 3, which in the central area of one of the Side surfaces 14 of the plate 2 or in the area of the middle or central transverse plane S is arranged. The second embodiment according to Figure 20 has two Friction elements 3, which are each arranged in the central area of the respective side surface 14 of the plate 2 or in each case in the area of the middle or central transverse plane S and thus opposite one another.

FIGS. 9, 10, 11 and 12 illustrate the structural design of the generators G1, G2 for the acoustic standing waves and the static rotational deformations of a possible embodiment of the actuator 1 of an ultrasonic motor according to the invention.

9 shows the bottom view of the actuator 1. FIG. 10 shows the

Front view of the actuator 1. FIG. 11 shows the top view of the actuator 1. FIG. 12 shows the rear view of the actuator 1.

The generators of acoustic standing waves and static waves

Rotational deformations G1 and G2 of the actuator 1 are formed from strip-shaped excitation electrodes 21 and strip-shaped general electrodes 22 arranged alternately on the main surfaces 12 and 13 of the piezoelectric plate 2 and the piezoceramic arranged between them. The term “main surfaces 12, 13” is understood to mean the surfaces on which the strip-shaped electrodes 21, 22 of the generators G1, G2, G3 and G4 are located.

In FIGS. 9 and 11, the arrows with the index p indicate the

Polarization directions of the piezoceramic between the electrodes 21 and 22. Here, the polarization directions of adjacent layers of piezoceramic material delimited by the respective electrodes 21 and 22 are aligned opposite and anti-parallel to one another, the polarization directions running perpendicular to the strip-shaped electrodes 21 and 22.

The generator G1 consists of the strip-shaped excitation electrodes 21 and generally strip-shaped electrodes 22 arranged on the main surfaces 12 and 13 of the part T1 of the plate 2, and the piezoceramic arranged between the electrodes 21 and 22.

The generator G2 consists of the strip-shaped excitation electrodes 21 arranged on the main surfaces 12 and 13 of the part T2 of the plate 2 and the general strip-shaped electrodes 22, and the piezoceramic arranged between the electrodes 21 and 22.

The strip-shaped excitation electrodes 21 of the generator G1 have the connection 23. The strip-shaped excitation electrodes 21 of the generator G2 have the connection 24. The general strip-shaped electrodes 22 of the generators G1 and G2 have the connection 25.

FIGS. 13, 14, 15 and 16 illustrate the structural design of the generators for the acoustic standing waves and the static longitudinal deformations G1, G2 of a further possible embodiment of the actuator 1 of an ultrasonic motor according to the invention. 13 shows the bottom view of the actuator 1, FIG. 14 shows the front view of the actuator 1, FIG. 15 shows the top view of the actuator 1 and FIG. 16 shows the rear view of the actuator 1.

The generators of acoustic standing waves and static waves

Longitudinal deformations G1 and G2 of the actuator 1 consist of the strip-shaped excitation electrodes 21 arranged alternately on the main surfaces 12 and 13 of the plate 2 and the strip-shaped general electrodes 22, and the piezoceramic arranged between them.

In FIGS. 13 and 15, the arrows with the index p indicate the

Polarization directions of the piezoceramic arranged in each case between the electrodes 21 and 22. Here, the polarization directions of adjacent layers of piezoceramic material delimited by the respective electrodes 21 and 22 are aligned opposite and anti-parallel to one another, the polarization directions running perpendicular to the strip-shaped electrodes 21 and 22.

The generator G1 consists of the strip-shaped excitation electrodes 21, the generally strip-shaped electrodes 22, arranged on the main surfaces 12 and 13 of the part T1 of the plate 2, and the piezoceramic arranged between the electrodes 21 and 22.

The generator G2 consists of the strip-shaped electrodes 21 and 21 arranged on the main surfaces 12 and 13 of the part T2 of the plate 2 the generally strip-shaped electrodes 22, and the piezoceramic arranged between the electrodes 21 and 22.

Figures 17, 18, 19 and 20 illustrate the structural design of the generators for the acoustic standing waves and the static longitudinal deformations G1, G2 of a further possible embodiment of the actuator 1 of an ultrasonic motor according to the invention.

17 shows the view from below of the actuator 1, FIG. 18 shows the

Front view of the actuator 1, FIG. 19 shows the top view of the actuator 1, and FIG. 20 shows the rear view of the actuator 1.

The generators of acoustic standing waves and static waves

Longitudinal rotational deformations G1 and G2 of the actuator 1 consist of the strip-shaped excitation electrodes 21 arranged alternately on the main surfaces 12 and 13 of the plate 2 and the strip-shaped general electrodes 22, and the piezoceramic arranged between them.

In FIGS. 17 and 19, the arrows with the index p indicate the

Polarization directions of the piezoceramic between the electrodes 21 and 22. The generators G1, G2 have different polarization directions for the ceramic between the electrodes 21 and 22, the polarization directions running perpendicular to the strip-shaped electrodes 21 and 22.

The generator G1 consists of the strip-shaped excitation electrodes 21 arranged on the main surfaces 12 and 13 of the part T1 of the plate 2 and the general strip-shaped electrodes 22, as well as the piezoceramic arranged between the electrodes 21 and 22.

The generator G2 consists of the strip-shaped electrodes 21 arranged on the main surfaces 12 and 13 of the part T2 of the plate 2, the generally strip-shaped electrodes 22, and the piezoceramic arranged between the electrodes 21 and 22.

The strip-shaped excitation electrodes 21 of the generator G1 have the connection 23. The strip-shaped excitation electrodes 21 of the generator G2 have the connection 24. The general strip-shaped electrodes

22 of the generators G1 and G2 have connection 25.

FIGS. 21, 22, 23 and 24 illustrate the structural design of an actuator of an ultrasonic motor according to the invention with four generators G1, G2, G3, G4 for acoustic standing waves and static longitudinal deformations.

21 shows the bottom view, FIG. 22 shows the front view, FIG.

23 shows the top view and FIG. 24 shows the rear view of the actuator 1.

The polarization directions of the piezoceramic of the gerators G1, G2, G3 and G4 between the electrodes 21 and 22 are directed opposite to one another, the polarization directions each running perpendicular to the strip-shaped electrodes 21 and 22.

In the actuator 1, the excitation electrodes 21 of the generator G3 have the connection 26 and the excitation electrodes 21 of the generator G4 have the connection 28.

In this embodiment of the generators, the strip-shaped electrodes 21, 22 run parallel to one another and also parallel to the plane S and parallel to the surfaces 15 and perpendicular to the surfaces 14.

25 shows the top view and FIG. 26 the bottom view of an actuator 1 of an ultrasonic motor according to the invention with two generators G1 and G2, in which the strip-shaped electrodes 21, 22 are parallel to one another and inclined to the transverse plane S at angles α and -a (Minus a) run.

27 shows the top view and FIG. 28 shows the bottom view of an actuator 1 of an ultrasonic motor according to the invention with four generators G1, G2, G3 and G4, the strip-shaped electrodes 21, 22 being parallel to one another and inclined to the transverse plane S at an angle a and -a (Minus a) run, and the strip-shaped electrodes 21, 22 run parallel to one another and inclined to the transverse plane S at the angle a and -a (minus a).

In the exemplary embodiments of the actuator 1 according to FIGS. 25 to 28, the angle of inclination α can be in the range from 0 to 45 °.

According to the invention, the generators G1, G2, G3 and G4 of the actuator 1 have the following special design features.

The distance k (see FIG. 9) between the adjacent strip-shaped excitation electrodes 21 and the general strip-shaped excitation electrodes 22 may be equal to or smaller than half the thickness D of the piezoelectric plate 2.

The width m (see FIG. 9) of the strip-shaped excitation electrodes 21, 22 can range between 0.1 and 1 mm.

The strip-shaped electrodes 21, 22 can be placed on the flake surfaces 12, 13 of the plate 2 by means of chemical deposition of nickel, or by thermal deposition of chromium, copper or nickel in a vacuum, or by ion plasma sputtering of chromium, copper, nickel, Gold or other similar processes.

[057] The structure or shape of the strip-shaped electrodes 21, 22 can be produced by laser milling, by chemical-lithographic etching, in the spray method over a mask or by other similar methods.

The number of strip-shaped electrodes 21, 22 on the surfaces 12 and 13 is only limited by the technological manufacturing possibilities.

In the above-described embodiments of the generators G1, G2, G3 and G4 with the strip-shaped exciter and general electrodes 21, 22, the piezoelectric charge constant d33 is used to excite acoustic standing waves.

29 shows a possible electrical circuit for operating an ultrasonic motor according to the invention with an actuator 1 with two generators G1, G2. The circuit consists of the coupling capacitors C1, C2 and the isolating resistors R1, R2. The capacitance of the coupling capacitors is equal to or greater than the capacitance C0 of the actuator 1 between the connections 23, 25 or 24.25 of the generators G1, G2. The isolating resistances R1, R2 are 5 to 10 times greater than that of the impedance X0 of the capacitance CO, where X0 = 1 / 6.28FaCo and Fa represents the operating frequency of the ultrasonic motor.

30 shows the block circuit of an embodiment for the electrical control device 27 of an ultrasonic motor according to the invention with two generators G1, G2 by means of electrical single-phase voltage. The circuit consists of the single-phase generator 29 for the electrical alternating voltage U1 at the output 30, the switch 31 with the connections 32, 33, 34, the generator 35 for static control of the electrical voltage Es at the output 36, the linear amplifiers 37 and 38 of the static electrical Voltage with the outputs 39, 40, at which the static electrical voltages E1 and E2 are applied, and the controller 41 with the input 42. All components of the electrical control device 27 have the common connection 43.

The invention provides that the control for the ultrasonic motor with the electrical control device 27 can take place in a static or dynamic manner.

The dynamic control of the illustrated ultrasonic motor with two generators G1, G2 is considered first.

In the dynamic control of this motor, single-phase and two-phase control are conceivable.

In the dynamic single-phase control of the motor, the generator 29 provides the electrical single-phase alternating voltage U1, the frequency Fg of which is equal to or close to the frequency Fa.

On the one hand, the voltage U1 is applied via the connection 32 of the changeover switch 31 and the capacitor C1 to the connection 23 of the excitation electrodes 21 of the generator G1. On the other hand, the voltage U1 is applied via the general connection 43 to the connection 25 of the general electrodes 22 of the generator G1.

The voltage U1 dynamically excites the generator G1, as a result of which the generator G1 in the actuator 1 generates the second mode of an acoustic standing wave propagating along the length L and along the width B. [068] FIGS. 31 and 32 illustrate the maximum deformations of the actuator 1, simulated using FEM calculations, when the second mode of an acoustic standing wave with the frequency fa, generated by the generator G1, propagates in it. This wave is an asymmetrical volume standing wave.

30, the changeover switch 31 is in the contact position with the connection 34, the electrical voltage U1 is applied via the capacitor C2 to the connection 24 of the electrodes 21 of the generator G2, whereby this generator is controlled dynamically.

The generator G2 excites a shaft in the actuator 1, whose FEM

Calculations of simulated maximum deformations are shown in Figures 33 and 34. The wave is a mirror image of the wave generated by the generator G1.

35 shows the electrical circuit of the actuator 1 with two generators G1, G2 for two-phase control of the motor.

36 shows the block circuit of the electrical control device 27 for a motor with two generators G1, G2 for an electrical two-phase voltage.

In the case of dynamic two-phase control, the generator 44 generates the electrical alternating voltages U1 and U2 of the same frequency Fg at the connections 45, 46, which is equal to the frequency Fa or is close to this frequency. The voltages U1 and U2 are shifted to one another by the angle f, which can be in the range from zero to plus or minus 180 °.

[074] The voltages U1 and U2 pass through the at the same time

Capacitors C1 and C2 to the connections 23 and 24 of the electrodes 21 and via the general connection 43 to the connections 25 of the electrodes 22 of the generators G1 and G2.

Due to the applied voltages U1 and U2, the generators G1 and G2 generate two acoustic standing waves in the actuator 1, the respective maximum deformations of which are shown in FIGS. 31 and 32 or 33 and 34. The waves generated are shifted to one another by the time t, where t is equal to f / 360 ° Fg. In the following, the dynamic control for the ultrasonic motor according to the invention, in which the actuator 1 has four generators G1, G2, G3 and G4, is considered.

37 shows a possible electrical circuit for

Two-phase control of an ultrasonic motor according to the invention with an actuator 1 with four generators G1, G2, G3 and G4, while FIG. 38 shows a possible block circuit of the electrical control device 27 of an ultrasonic motor according to the invention with an actuator with four generators G1, G2, G3 and G4 for its two-phase control .

In the case of dynamic single-phase control, the generator 29 provides an electrical single-phase alternating voltage U1, the frequency Fg of which is equal to the frequency fa or is close to this frequency.

On the one hand, the voltage U1 is applied via the connection 32 of the switch 31 and the capacitors C1, C3 to the connections 23, 26 of the excitation electrodes 21 of the generators G1, G3 and, on the other hand, the voltage U1 is applied via the general connection 43 the connection 25 of the general electrodes 22 of the generators G1, G3.

The voltage U1 dynamically excites the generators G1, G3, as a result of which the generators G1, G3 in the actuator 1 generate the fourth mode of an acoustic standing wave that propagates along its length L and along its width B.

FIGS. 39 and 40 show the shape of the maximum deformations of the actuator 1 when the fourth mode of an acoustic standing wave of the frequency Fa propagates in it, generated by the generators G1, G3. This wave is an asymmetrical volume standing wave. If the changeover switch 31 is in the contact position with the connection 34 (see Fig.

38), the electrical voltage U1 is applied via the capacitors C2, C4 to the connections 24, 28 of the electrodes 21 of the generators G2, G4, as a result of which they are dynamically excited. The generators G2, G4 generate a wave in the actuator 1, the shape of which with maximum deformations is shown in FIGS. 41, 42. This wave is a mirror image of the wave generated by the generators G1, G3, the shape of which is shown with maximum deformation in FIGS. 39 and 40.

43 shows a possible electrical circuit for a

Two-phase control of an ultrasonic motor according to the invention with an actuator 1 with four generators G1, G2, G3, G4, while FIG. 44 shows a possible block circuit of the electrical control device 27 of an ultrasonic motor according to the invention with an actuator with four generators G1, G2, G3, G4 for its two-phase control .

In a dynamic two-phase control, the generator 44 provides the electrical alternating voltages U1 and U2 of the same frequency Fg at its connections 45, 46, which is equal to the frequency fa or is close to this frequency. The voltages U1 and U2 are shifted to one another by the angle f, which can be in the range from zero to plus or minus 180 °.

The voltages U1 and U2 reach the connections 23, 26 and 24, 28 of the electrodes 21 via the capacitors C1, C3 and C2, C4 and via the general connection 43 to the connections 25 of the electrodes 22 of the generators G1, G3 and G2, G4.

Due to the applied voltages U1 and U2, the generators G1, G3 and G2, G4 generate two acoustic standing waves in the actuator 1, the form of maximum deformations of which is shown in FIGS. 39 and 40 and in FIGS. 41 and 42. The waves generated are shifted from one another by the time t, which is equal to f / 360 ° Fg.

The generation of the acoustic standing waves in the actuators 1, the generators G1 to G4 of which have electrodes 21, 22 inclined by the angle α (corresponding to FIGS. 25 to 28), is carried out in the same way as for the generators G1 to G4 parallel to the transverse plane S arranged electrodes 21, 22.

If inclined electrodes 21, 22 are used, the acoustic standing waves differ somewhat in terms of their shape from those in FIGS. 31 to 34 and the forms shown in FIGS. 39 to 42, but this does not change the essence of the invention.

45 illustrates the frictional contact of the friction element 3 with the friction layer 5 and the driven element 6. Via the friction surface 47, the points of which contact the friction layer 5, the friction element 3 is in contact with the friction layer 5 5 and the frictional force forming the friction surface 47, an operative connection is created between the two. The point 48 represents one of the points belonging to the friction surface 47.

The figures 50, 52, 55, 56, 58, 60, 62, 64, 66, 68 of FIG. 46 show possible trajectories of the point 48. In the case of a single-phase excitation of the actuator 1 (see FIGS. 29 to 32) the works ultrasonic motor according to the invention as follows:

If an acoustic standing wave (see FIGS. 29 to 32 or FIGS. 37 to 40) is generated by the generator G1 or the generators G1, G3 in the actuator 1, the point 48 moves on the inclined trajectory 49 shown in position 50 the friction element 3 causes the driven element 6 to move in the direction shown in FIG. 45 with arrows with the index V.

If a mirror-image acoustic standing wave (see FIGS. 29, 30, 33, 34 or FIGS. 37, 38, 39, 40) is generated by the generator G2 or the generators G2, G4 in the actuator 1, the point 48 moves on the linear movement path 51, which is inclined in the opposite direction (see Figure 52).

As a result, the friction element 3 causes the driven element 6 to move in the opposite direction shown in FIG. 45 with arrows with the index -V.

With two-phase excitation of the two generators G1 and G2 (see FIGS. 35 and 36) or the four generators G1, G3 and G2, G4 (see FIGS. 43 and 44), two acoustic standing waves are generated in the actuator 1 at the same time. Figures 31 to 34 or Figures 39 to 42 show the shapes of the waves generated. Due to the propagation of the acoustic standing waves in the actuator 1, the points of the friction surface 47 of the friction element 3 and accordingly the point 48 can be on inclined elliptical movement paths 53, 54 (shown in Figures 55, 56) or on circular movement paths 57 (shown in Figure 58) or on linear vertical trajectories 59 (shown in Figure 60) or on linear longitudinal trajectories 61 (shown in Figure 62) or on vertical elliptical trajectories 63 (shown in Figure 64) or on horizontal elliptical trajectories 65 (shown in Figure 66 ) or move on asymmetrical movement paths 67 (shown in Figure 68).

The shape of the movement path is determined by the dimensions of the plate 2 of the actuator 1 and the phase or time shift between the acoustic standing waves propagating in the actuator 1. When the material points 48 of the friction surface 47 move on the movement paths 49, 51, 53, 54, 57, 63, 65, 67, the actuator 1 transmits a force to the driven element 5, whereby the driven element 5 moves or develops its maximum force .

The stated shapes of movement paths of the material points of the friction surface 47 make it possible to implement different modes of operation for the ultrasonic motor according to the invention.

The movement paths 59 and 61 make it possible to reduce the friction between the friction layer 5 and the friction surface 47.

In a dynamic control of the motor according to the invention, the maximum step length of the driven element 5 is not restricted. The minimum step length of the driven element 5 is determined by the roughness of the friction layer 5 and the friction surface 47. In the best case, the step length is between 0.1 and 0.05 pm, which determines the resolving power of the motor.

The static control of the motor according to the invention takes place as follows:

First, the dynamic control is turned off. Come one

Single-phase control device 27 is used, the changeover switch 31 is in the Contact position with the connection 33 (see Figures 30, 38) brought.

In this position of the switch 31, the generators G1, G2, G3, G4 are not dynamically excited, i. H. no electrical voltage U1 reaches the electrodes 21, 22 (see FIGS. 29, 37).

If a two-phase control device 27 is used, the generator 44 is switched off (see FIGS. 36, 44). The voltage amplitudes U1 and U2 are zero and the generators G1, G2, G3, G4 are not dynamically excited.

The generator for the static voltage 35 provides at its output 36 a static control voltage Es, which can change in the range of + Es ... 0 ... -Es. This voltage is amplified by the linear amplifiers 37, 38. As a result, the static voltage E1 is present at the output 39 of the amplifier 37, which voltage can change in the range from + E ... 0 ...- E. The inverted static voltage E2, which can change in the range from -E ... 0 ... + E, acts at the output 40 of the amplifier 38.

In the ultrasonic motor according to the invention, the generators of the acoustic standing waves G1, G2, G3, G4 also form the generators for the static rotational deformations of the piezoelectric plate 2 of the actuator 1. Therefore, the static control of the ultrasonic motor takes place with the help of the generators G1, G2 or of the generators G1, G2, G3, G4. It does this as follows.

On the one hand, the voltage E1 is applied via the resistors R1 and R4 to the connections 23 and 28 of the excitation electrodes 21 of the generators G1 and G4. On the other hand, the voltage E1 is applied via the general connections 43 to the connections 25 of the general electrodes 22 of the generators G1 and G4.

On the one hand, the voltage E2 is applied via the resistors R2 and R3 to the connections 24 and 26 of the excitation electrodes 21 of the generators G2 and G3. On the other hand, the voltage E1 is applied via the general connections 43 to the connections 25 of the general electrodes 22 of the generators G2 and G3.

47 illustrates the actuator 1 with two generators G1 and G2 in a position in which the static voltages E1 and E2 are zero. In In this case, all areas between the electrodes 21 and 22 of the generators G1, G2 are not deformed, are equal to one another and equal to k, the friction element 3 is - with respect to the plane S - arranged symmetrically in its central position.

48 uses an FEM calculation to illustrate the actuator 1 with two generators G1 and G2 in a position in which the static voltage E1 is equal to -E and the static voltage E2 is equal to + E. In this case, the areas between the electrodes 21 and 22 of the generators G1 (see FIG. 48) are compressed and are equal to k-x, where x is the magnitude for the elementary compression.

The areas between the electrodes 21 and 22 of the generators G2

(see Fig. 40) are stretched and are equal to k + x, where x is the magnitude value for the elementary stretching.

In the area of the piezoceramic under the friction element, a rotational deformation or torsion of the plate material occurs in a plane which is arranged essentially parallel to the main sides of the actuator plate, as shown in FIG. 48 with the arrow 83. In this case, the friction element 3 experiences a counterclockwise rotating or tilting movement. The points 48 of the friction surface 47 of the friction element 3 are shifted to the left by the amount d = nx, based on the transverse plane S, where d is greater, the greater the number of distances n between the electrodes 21 and 22 of the generator G1 or of the generator G2. The advance of the points 48 of the friction surface 47 of the friction element 3 is greater than the advance of the points lying on the base surface of the friction element. The generated tilting of the friction element enables a far greater advance of the driven element in comparison to an advance caused by longitudinal expansions. The higher the friction element, the greater the feed generated due to its tilting.

49 uses an FEM calculation to illustrate the actuator 1 with two generators G1 and G2 in a position in which the static voltage E1 is equal to -E and the static voltage E2 is equal to + E. In this case, all areas between the electrodes 21 and 22 of the generators G1 (see FIG. 49) are stretched and equal to k + x.

The distances between the electrodes 21 and 22 of the generators G2 (FIG. 49) are compressed and equal to k-x.

In the area of the piezoceramic under the friction element, a rotational deformation or torsion of the plate material occurs in a plane which is arranged essentially parallel to the main sides of the actuator plate, as shown in FIG. 49 with the arrow 83. In this case, the friction element 3 experiences a clockwise rotating or tilting movement. The points 48 of the friction surface 47 of the friction element 3 are shifted to the right by the amount d = nx with respect to the transverse plane S, where n is the number of distances between the electrodes 21 and 22 of the generator G1 or the generator G2. The advance of the points 48 of the friction surface 47 of the friction element 3 is greater than the advance of the points lying on the base surface of the friction element. The generated tilting of the friction element enables a far greater advance of the driven element in comparison to an advance caused by longitudinal expansions. The higher the friction element, the greater the feed generated when it is tilted.

50 clearly shows the actuator 1 with two generators G1 and G2 and FIG. 53 shows the actuator 1 with four generators G1, G2, G3 G4 in a position in which the static voltages E1 and E2 are zero. In this case, all areas between the electrodes 21 and 22 of the generators G1, G2, G3, G4 are not deformed, are equal to one another and equal to k, the friction element 3 is arranged symmetrically in its central position with respect to the plane S.

51 clearly shows the actuator 1 with two generators G1 and G2; FIG. 54 shows the actuator 1 with four generators G1, G2, G3 G4 in a position in which the static voltage E1 is equal to -E and the static stress E2 is equal to + E. In this case, the areas between the electrodes 21 and 22 of the generators G1 (see Fig. 51) or G1, G4 (see Fig. 54) are compressed and are equal to kx, where x is the magnitude for the elementary compression.

The areas between the electrodes 21 and 22 of the generators G2 (see FIG. 51) or G2, G3 (see FIG. 54) are stretched and are equal to k + x, where x is the value for the elementary stretching.

In this case, the friction element 3 - with respect to the transverse plane S - is shifted to the left by the amount x = nx, where n is the number of distances between the electrodes 21 and 22 of the generator G1 or the generators G1, G3.

52 clearly shows the actuator 1 with two generators G1 and G2, and FIG. 55 shows the actuator 1 with four generators G1, G2, G3 G4 in a position in which the static voltage E1 is equal to + E and the static voltage E2 is equal to -E.

In this case, all areas between the electrodes 21 and 22 of the generators G1 (see FIG. 52) or G1, G4 (see FIG. 55) are stretched and equal to k + x, while the distances between the electrodes 21 and 22 of the generators G2 (see Fig. 52) or generators G2, G3 (see Fig. 55) are compressed and equal to k + x.

In this case, the friction element 3 - based on the transverse plane S - is shifted to the right by the amount x = nx, where n is the number of distances between the electrodes 21 and 22 of the generator G1 or the generators G1, G3.

In all cases, the expansion and compression of the piezoceramic between the electrodes 21 and 22 takes place due to the reverse piezo effect, the magnitude of the elementary expansion or the elementary compression being determined by the piezoelectric charge constant d33.

By the continuous simultaneous change of the electrical

Tension E1 in the range from + E via zero to -E and the tension E2 from -E via zero to + E, it is possible for the friction element 3 to be static to tilt the value X to the left or right of its middle position or to move the friction surface.

56 illustrates the actuator 1 with two generators G1 and G2 in a position in which the static voltages E1 and E2 are zero. In this case, all areas between the electrodes 21 and 22 of the generators G1, G2 are not deformed, are equal to one another and equal to k, the friction element 3 is symmetrically arranged in its central position relative to the plane S.

57 illustrates, by means of an FEM calculation, the actuator 1 with two generators G1 and G2 in a position in which the static voltage E1 is equal to -E and the static voltage E2 is equal to + E. In this case, the areas between the electrodes 21 and 22 of the generators G1 (see Fig. 57) are compressed and are equal to kx, where x is the magnitude value for the elementary compression, while the areas between the electrodes 21 and 22 of the generators G2 ( see Fig. 58) and are equal to k + x, where x is the size value for the elementary elongation.

In the area of the piezoceramic below the friction element, a longitudinal torsional deformation or a longitudinal torsional deformation of the plate material occurs in a plane which is arranged essentially parallel to the main sides of the actuator plate, as shown in FIG. 57 with the arrow 82. In this case, the friction element 3 experiences a counterclockwise rotating or tilting movement. The points 48 of the friction surface 47 of the friction element 3 are shifted to the left by the amount d = nx, based on the transverse plane S, where d is greater, the greater the number of distances n between the electrodes 21 and 22 of the generator G1 or of the generator G2. The advance of the points 48 of the friction surface 47 of the friction element 3 is greater than the advance of the points lying on the base surface of the friction element. The generated tilting of the friction element enables a far greater advance of the driven element in comparison to an advance caused by longitudinal expansions. The higher it is The friction element is, the greater the feed generated when it is tilted.

58 uses an FEM calculation to illustrate the actuator 1 with two generators G1 and G2 in a position in which the static voltage E1 is equal to -E and the static voltage E2 is equal to + E. In this case, all areas between the electrodes 21 and 22 of the generators G1 (see FIG. 58) are stretched and equal to k + x. The distances between the electrodes 21 and 22 of the generators G2 (see FIG. 58) are compressed and equal to k-x.

In the area of the piezoceramic below the friction element, a longitudinal torsional deformation or a longitudinal torsional deformation of the plate material occurs in a plane which is arranged essentially parallel to the main sides of the actuator plate, as shown in FIG is. In this case, the friction element 3 experiences a clockwise rotating or tilting movement. The points 48 of the friction surface 47 of the friction element 3 are shifted to the right by the amount d = nx, relative to the plane S, where n is the number of distances between the electrodes 21 and 22 of the generator G1 or the generator G2. The advance of the points 48 of the friction surface 47 of the friction element 3 is greater than the advance of the points lying on the base surface of the friction element. The generated tilting of the friction element enables a far greater advance of the driven element in comparison to an advance caused by longitudinal expansions. The higher the friction element, the greater the feed generated when it is tilted.

The maximum displacement X is determined by the maximum values of the voltages E1, E2 and is limited by the level of the breakdown voltage between the electrodes 21 and 22. The actual maximum value is in the range of about 10 nm. There is no lower limit to the value. 59 illustrates the frictional contact of the friction element 3 with the friction layer 5 of the driven element 6 in the case of a static control of the motor according to the invention.

With both static and dynamic control of the motor according to the invention, all material points of the friction surface 47 of the friction element 3 are pressed against the friction layer 5 of the driven element 6.

When the friction element 3 is shifted to the left (see FIGS. 48, 51, 54, 57) or to the right (see FIGS. 49, 52, 55, 58) - in relation to its middle position (see FIGS. 47, 50, 53, 56) - the material points of the friction surface 47 move on an approximately linear 69 or curved 70 movement path (see FIG. 59) and move the driven element 6 to the left or right due to the friction.

The maximum displacement of the driven element 6 is + X or -X (+/- 10nm), while the minimum displacement of the friction element or the resolving power of the proposed motor are not limited.

FIGS. 71 and 72 of FIG. 60 show embodiments of sound-absorbing stops 10 which fix the actuator 1.

The stops 10 shown in Figure 71 have a thin, oscillating wall 75 which is in contact with the end face 15 of the piezoelectric plate 2 of the actuator 1. The wall 2 oscillates together with the surface 15, and this practically without damping of the actuator 1.

The stops 10 shown in Figure 72 have oscillating wings 75 which are in contact with the end face 15. The wings 75 oscillate together with the surface 15, and this practically without damping the actuator 1.

The stop 10 shown in Figure 73 has a frame 77 oscillating with it and a support 78 oscillating with it. All stops have fastening openings 79. The actuator 1 is arranged between two stops 10 (see FIGS. 1, 2, 3, 4). If the friction element 3 wears out, the actuator 1 can move parallel to itself in the direction of the driven element 6 due to the force of the spring 4. If the driven element 6 has a slight uneven running, it is possible for the actuator 1 to oscillate around its middle position. In both cases, the surfaces 15 of the actuator 1 “slide” with minimal friction on the surfaces of the mountings 10 (see FIGS. 1, 2, 3, 4).

To reduce friction, the brackets 10 can have balls or rollers 80 and the surface 15 can have a protective covering 81, see Figure 73. In this embodiment, the end faces 15 of the actuator 1 roll on the balls or rollers over the surfaces of the brackets 10.

61 shows a possibility of fastening the actuator 1 for the motor according to the invention, in which the actuator 1 has a support 83 firmly connected to the surface 14 of the plate 2. With this fastening, the actuator 1 rotates about the support 83 in the direction of the driven element 6 or swings about its middle position. The advantage of this construction is that the actuator 1 wedges in one of the effective directions of the pretensioning force of the motor, as a result of which it guides the driven element 6 with absolute precision.

62 shows an engine construction with two actuators 1. In this one

Motor, both actuators 1 are wedged by the opposing biasing forces of the motor.

With the proposed invention it is possible to increase the resolving power of ultrasonic motors to the extent that it can be measured with existing devices. By replacing ultrasonic motors with static multilayer actuators with the ultrasonic motor according to the invention, it is possible to reduce the costs of high-precision devices and to expand the field of application of ultrasonic motors.

List of reference symbols:

1: ultrasonic actuator

2: piezoelectric plate

3: friction element

4: spring : Friction layer: driven element: displaceable body: bearing: housing 0: stop 1: embodiment of the driven element 6 as rotating or rotating body 2, 13: main surfaces 4: side surfaces 5: end surfaces 6: intersection of plane S 7, 18: embodiments of the ultrasonic actuator 1 with two

Generators G1, G2 9, 20: embodiments of the ultrasonic actuator 1 with four

Generators G1, G2, G3, G4 1: excitation electrode 2: general electrode 3: connection (of generator G1) 4: connection (of generator G2) 5: connection of general electrode (s) 22 6: connection of excitation electrode (s) 21 7: electrical control device 8: connection of the excitation electrode (s) (of the generator G4) 9: single-phase generator 0: output of the single-phase generator 29 1: changeover switch 2-34: changeover switch connections 5: generator (for static control of the electrical

Voltage) 6: output of generator 35 7, 38: linear amplifier 9, 40: outputs of linear amplifier 37, 38 41: controller

42: Controller input

43: common connection of the electrical

Control device 27

44: Generator (for electrical alternating voltages)

45, 46: Connections of the generator 44

47: friction surface

48: Point of the friction surface 47

49-70: trajectories of point 48

71-74: different embodiments for the stop 10

75: swinging wall

76: swinging wing

77: swinging frame

78: vibrating beam

79: Fixing openings

80: roles

81: protective covering

82. Arrow to clarify the deformation

83: support

84: arrow indicating the direction of rotation

G1-G4: Generators of acoustic standing waves and static waves

Deformations (of the ultrasonic actuator 1)

Claims

Expectations

Claim 1. Ultrasonic motor comprising an ultrasonic actuator (1) in the form of a rectangular piezoelectric plate (2) with two main surfaces (12, 13), two side surfaces (14), two end surfaces (15) and generators arranged in two or four areas of the piezoelectric plate (G1, G2, G3, G4) for acoustic standing waves, the piezoelectric plate being divided by one or three transverse planes perpendicular to its side faces and parallel to its end faces, and further comprising at least one driven element (6) and an electrical control device (27 ), with at least one friction element (3) being arranged on the ultrasonic actuator (1), which is pressed against the at least one driven element (6), characterized in that the generators (G1, G2, G3, G4) of the acoustic standing waves are also generators static torsional deformations or static longitudinal torsional deformations or static longitudinal deformations of those areas of the represent piezoelectric plate, which are each arranged below the friction element (3) between two adjacent generators, the static deformations taking place essentially in a plane arranged parallel to the main surfaces (12, 13) of the piezoelectric plate (2).

Claim 2. Ultrasonic motor according to claim 1, characterized in that the generators (G1, G2, G3, G4) of the acoustic standing waves and the static deformations as strip-shaped excitation electrodes (21) and general strip-shaped electrodes arranged alternately on the main surfaces (12, 13) (22) are executed, wherein the strip-shaped electrodes (21, 22) run parallel or at an angle or perpendicular to the side surfaces (14) of the piezoelectric plate (2) and the polarization directions of the piezoelectric plate between the strip-shaped electrodes (21, 22 ) run perpendicular to these.

Claim 3. Ultrasonic motor according to claim 1 or 2, characterized in that by one or two generators (G1, G2) for acoustic standing waves in the piezoelectric plate (2) the second or fourth mode of a acoustic standing wave is generated, which propagates along the length L and along the width B of the piezoelectric plate (2).

Claim 4. Ultrasonic motor according to one of the preceding claims, characterized in that a friction element (3) is arranged centrally on one of the side surfaces (14) of the piezoelectric plate (2) or in each case a friction element (3) is arranged centrally on each of the two side surfaces (14 ) of the piezoelectric plate are arranged.

Claim 5. Ultrasonic motor according to one of the preceding claims, characterized in that the ratio of length to width of the piezoelectric plate (2) is in the range from 2 to 3 or from 4 to 6.

Claim 6. Ultrasonic motor according to one of the preceding claims, characterized in that the thickness D of the piezoelectric plate (2) is smaller than its width B.

Claim 7. Ultrasonic motor according to one of the preceding claims, characterized in that a distance k between adjacent excitation electrodes (21) and general strip-shaped electrodes (22) is equal to or smaller than half the thickness D of the piezoelectric plate (2).

Claim 8. Ultrasonic motor according to one of the preceding claims, characterized in that the driven element (6) is designed as a longitudinally displaceable body or as a rotary body (11).

Claim 9. Ultrasonic motor according to one of the preceding claims, characterized in that the electrical control device (27) provides an electrical single-phase voltage, which excite one or two generators for acoustic standing waves and two static electrical voltages, the static two or four generators for acoustic standing waves and deform static longitudinal deformations.

Claim 10. Ultrasonic motor according to one of the preceding claims, characterized in that the electrical control device (27) provides an electrical two-phase voltage, which simultaneously excites two or four generators for acoustic standing waves and two static electrical voltages, the statically two or four generators of acoustic standing waves and deform from static torsional deformations.