EP3465783A1

EP3465783A1 - Ultrasonic motor having a diagonally excitable actuator plate

Info

Publication number: EP3465783A1
Application number: EP17733346.5A
Authority: EP
Inventors: Wladimir Wischnewskiy; Alexej Wischnewski
Original assignee: Physik Instrumente PI GmbH and Co KG
Current assignee: Physik Instrumente PI GmbH and Co KG
Priority date: 2016-06-01
Filing date: 2017-05-31
Publication date: 2019-04-10
Also published as: JP2019517767A; WO2017206992A1; CN109314176A; CN109314176B; DE102016110124B4; US11043908B2; US20190140559A1; JP6785318B2; DE102016110124A1

Abstract

The invention relates to an ultrasonic motor, comprising an ultrasonic actuator (1) in the form of a rectangular piezoelectric plate (2), which has two generators (23, 24) for acoustic standing waves and on which at least two friction elements (3) are arranged, an element to be driven, and an electric excitation device. The piezoelectric plate of the actuator is divided into two pairs of sections lying diagonally opposite by two virtual planes (S1, S2), which extend perpendicularly to each other and which extend through the center line of the main surfaces of the actuator, wherein each of the generators (23; 24) consists of two parts (25+26; 27+28), which can be operated in an antiphase manner and each of which is arranged in a diagonal section of the piezoelectric plate, and the friction elements (3) are arranged on one or two end faces (10) of the piezoelectric plate (2).

Description

ULTRASONIC MOTOR WITH DIAGONALLY RECALLABLE ACTUATOR PLATE

The invention relates to an ultrasonic motor according to claim 1.

From DE 10 2014 209 419 B3 an ultrasonic motor is known, in

which the ultrasonic actuator as a rectangular piezoelectric plate with generators for acoustic diagonal waves and two

Friction elements is executed on it. The generators of the acoustic waves of this engine consist of two electrically connected parts. This leads to an increase of the electrical excitation voltage of the motor by two times. In addition, the well-known

Construction by a significant difference in the shape of the trajectory of the friction elements, which in turn has an increased abrasion of its friction contact result and leads to a reduction in the life of the motor. In addition, the difference in the shape of the trajectories of the friction elements causes a high unevenness of the movement of the driven

Elements at low movement speeds. All this together narrows the field of application of this engine.

The object of the invention is therefore to provide an ultrasonic motor which can be operated with a lower electrical excitation voltage, which has a reduced abrasion within the friction contact, and which has a longer service life and improved

Having uniformity of movement of the driven element at low speeds.

This object is achieved by an ultrasonic motor according to claim 1, wherein the subsequent dependent claims represent at least expedient developments.

In the following, the terms 'ultrasonic actuator' and 'actuator' in

used synonymously.

It is assumed that an ultrasonic motor, the one

Ultrasound actuator in the form of a rectangular piezoelectric plate having two major surfaces in terms of area and the two major surfaces interconnecting side surfaces, wherein the Ultrasonic actuator has two generators for generating acoustic standing waves and at least two arranged on at least one of the side surfaces friction elements. Furthermore, the ultrasonic motor has a driven element and an electrical exciter device.

The piezoelectric plate of the actuator can by two to each other

perpendicular virtual planes passing through the centerline of its major faces are divided into two pairs of diagonally opposite sections, each of the generators consisting of two antiphase operable parts, each arranged in a diagonal section of the piezoelectric plate, and the friction elements a side surface, which represents an end face, or are arranged on two opposite end faces.

It may be advantageous that the piezoelectric plate has the shape of a square or a parallelepiped.

Likewise, it may be advantageous that the generators of the acoustic standing waves have a three-layer or a multi-layer structure, consisting of layers of exciter electrodes, of layers

common electrodes and layers of piezoelectric ceramic between them.

Furthermore, it may be advantageous that by the generators for

standing acoustic waves in the actuator of the ultrasonic motor diagonal acoustic standing waves can be generated, which propagate in the direction of one or both diagonals of one of the main surfaces of the piezoelectric plate.

Furthermore, it may be advantageous that the electrical exciter device of the actuator has a switch for connecting the one or the other generator for acoustic waves with the actuator controlled by the electrical voltage.

In addition, it may be advantageous that the electrical

Exciter device has a block which is an electrical

Additional voltage generated to excite the second generator acoustic waves. It may be advantageous that the block is the phase of

changes electrical voltage in proportion to the phase of the primary electric voltage.

In addition, it may be advantageous that the block the amplitude of the

electrical additional voltage changes.

[0015] FIG.

Fig. 1: embodiment of an ultrasonic motor according to the invention

FIG. 2: Ultrasonic actuator of the ultrasonic motor according to FIG. 1 in FIG

perspective view

3 shows different views of the ultrasonic actuator according to FIG. 1 in the illustrations 17 to 20

Fig. 4: embodiment of an ultrasonic actuator of an inventive

ultrasonic motor

Fig. 5: embodiment and internal structure of an ultrasonic actuator of an ultrasonic motor according to the invention

Fig. 6: embodiment and internal structure of an ultrasonic actuator of an ultrasonic motor according to the invention

FIG. 7 shows two different connecting diagrams (illustrations 52 and

55) for connecting the ultrasonic actuator of an inventive

Ultrasonic motor with an electrical excitation device

8: Representations 57 and 58: Ansteuer- or excitation principle of

Ultrasonic actuator according to the connection diagram according to illustration 52 of FIG.

7; Figures 59 and 60: Driving principle of the

Ultrasonic actuator according to the connection diagram according to illustration 55 of FIG. 7 FIG. 9: Calculated or simulated maximum deformations of a

Training of standing waves in him excited ultrasound actuator of an ultrasonic motor according to the invention

FIG. 10 shows the movement paths of the ultrasound actuators of an ultrasound motor according to the invention. FIG

friction

11 shows an embodiment of an ultrasonic motor according to the invention. FIG. 1 shows a possible embodiment of an ultrasonic motor according to the invention, comprising an ultrasonic actuator 1 in the form of a rectangular piezoelectric plate 2 having two major surfaces in terms of area and four side surfaces connecting the two major surfaces, wherein two spaced apart at one of the side surfaces, which is an end face of the Ultraschallaktors

Friction elements 3 are arranged such that each of the

Friction elements adjacent to the end face of each adjacent side surface of the Ultraschallaktors. The actuator 1 is held or mounted in a housing 4 via holders 5. The friction elements 3 are pressed against the friction layer 6 of the driven element 7, which is mounted linearly movable or displaceable on ball bearings 8.

Fig. 2 shows the piezoelectric plate 2 of the actuator 1 of Fig. 1 in detail.

The plate 2 has a length L, a width B and a thickness D. It has the side surfaces 9, the end surfaces 10 and the largest in terms of area

Main surfaces 11. The end surfaces 10 are those side surfaces which, in the assembled state of the ultrasonic motor, are turned towards or away from the element 7 to be driven and on which the friction elements 3 are arranged.

If the length L is equal to the width B, the plate has the shape of a square. If the length L is not equal to the width B, the plate has the shape of a parallelepiped. The plate 1 can be divided into the two pairs of diagonally opposite sections 12, 13 and 14, 15 by two mutually perpendicular virtual planes S1 and S2. The planes S1 and S2 pass through the normal of the center lines 16 of the main surfaces 11 and perpendicular to them.

3 shows the front view of the plate 2 of the actuator 1 of Fig. 1 and Fig. 2. The representations 18 and 19 of Fig. 3 show the bottom view and the top view of the plate 2, while representation 20 of Fig. 3 shows the rear view of the plate 2. Along the two diagonal 21 and 22, the corresponding two pairs of diagonal sections 12, 13 and 14, 15 are arranged. The piezoelectric plate 2 comprises two generators 23 and 24 for generating standing acoustic waves, wherein each of the generators 23 and 24 consists of the two antiphase driven parts 25, 26 and 27, 28. The part 25 belongs to Section 12, Part 26 belongs to Section 13, Part 27 belongs to Section 14 and Part 28 belongs to Section 15.

In the construction of the plate 2 shown in Fig. 3, the generators have

23 and 24 a three-layer structure. Each part 25, 26 and 27, 28 of the generators 23 and 24 comprises a layer with a common electrode 29, a layer with an excitation electrode 30, 31 and a layer of piezoelectric ceramic 32 between them. The electrodes 29, 30, 31 are arranged on the main surfaces of the plate 2. The entire piezoceramic of the plate 2 is polarized in the direction shown in FIG. 3 by arrows with the index p. The common electrodes 29 of the generators 23 and 24 have the terminals 33, the

Exciting electrodes 30 of the generator 23 have the terminals 34 and the excitation electrodes 31 of the generator 24 have the terminals 35.

4 shows in the illustrations 36 to 39, another constructive design of an ultrasonic actuator 1 of an inventive

Ultrasonic motor with three-layer structure of the generators 23, 24 for the diagonal acoustic standing waves. The illustration 36 shows the front view, the illustrations 37 and 38 respectively show the bottom view and the top view, and the illustration 39 shows the rear view. In this constructive embodiment of the ultrasonic actuator, the common electrodes 29 of the generators 23 and 24 are interconnected.

Representation 40 of Fig. 5 shows the top view of an ultrasonic actuator 1, in which the generators 23 and 24 have a multilayer structure and constitute multi-layer generators. The illustration 41 shows the corresponding side view of such an ultrasonic actuator. The illustrations 42, 45 and 43, 44 show the structure of the antiphase driven parts 25, 26 and 27, 28 of the multi-layer generators 23 and

24 of diagonal acoustic standing waves. Each part 25, 26 and 27, 28 consists of alternating layers of excitation electrodes 30 and 31, layers of common electrodes 29 and piezoceramic layers 32 between them. Fig. 6 shows a further constructive embodiment of an ultrasonic actuator of an ultrasonic motor according to the invention with multi-layer generators

23 and 24 for generating diagonal standing acoustic waves. Figure 46 shows the top view of such an ultrasonic actuator while

Figure 47 shows the side view of the ultrasonic actuator. The

Representations 48, 51 and 49, 50 show the structure of the antiphase driven parts 25, 26 and 27, 28 of the multi-layer generators 23 and

24 for diagonal acoustic standing waves. As in the embodiment of the ultrasonic actuator according to FIG. 5, here the electrode layers 29, 30, 31 are arranged parallel to the main surfaces 11 of the plate 2.

The representation 52 of FIG. 7 shows a first connection diagram for

Connecting the piezoelectric plate 2 of the ultrasonic actuator 1 of an ultrasonic motor according to the invention with the electrical

Excitation device 53. The electrical excitation device 53 generates the alternating electrical voltage U1 whose frequency is equal to the

Resonant frequency of the second mode of the acoustic standing wave which propagates along or is close to the diagonal 22 or 21 of the piezoelectric plate 2. The voltage U1 is applied via the switch 54 to the common electrodes 29 and to the

Excitation electrodes 31 or 30 of the generators 24 or 23 laid. In the case of the ultrasonic motor according to the invention, the parts 27, 28 and 25, 26 of the generators 24 and 23 are designed or driven in antiphase to generate the second mode of the diagonal acoustic wave. The parts are connected to each other in parallel with the voltage U1.

Representation 55 of FIG. 7 shows a second connection diagram for

Connecting the piezoelectric plate 2 of the actuator 1 a

according to the invention with the electric motor

Excitation device 53, wherein the electrical excitation device 53 with a block 56 an additional electrical voltage U2 with the same

Frequency like the voltage U1 provided. Depending on the selected operating regime of the motor, the voltage U2 can be phase-shifted with respect to the voltage U1, namely by an angle in the range of zero to plus or minus 180 °. During engine operation this angle can be varied. In addition, the amplitude and the voltage U2 can be changed.

The representations 57, 58 and 59, 60 of Fig. 8 show the top view of the actuator 1 according to FIG. 2 or 3 or as shown in FIG. 5 or 6. Die

Friction elements 3 are each arranged on one of the two end faces 10 of the ultrasonic actuator 1. In Fig. 8, the antiphase nature of the parts of the generators 25, 26 and 27, 28 is indicated by the index +/-. By the term antiphase of the parts 25, 26 and 27, 28 is meant that each of the parts causes a deformation in the plate 2 which is opposite in relation to the other part.

The illustrations in FIG. 8 serve to explain the two principles for exciting the actuator 1 by the corresponding connection diagrams illustrated in FIG. 7. In the first principle, during operation of the motor by means of the electrical voltage U1, only one generator, i. either only the generator 24 (representation 58 in FIG. 8), or only the generator 23

(Representation 57 in Fig. 8) driven. The switching of the voltage takes place with the aid of the change-over switch 54 (see illustration 52 in FIG. 7). In this case, generates the excited by the voltage U1 generator 24 or

Generator 23 in the actuator 1, the second mode of the diagonal acoustic standing wave, which propagates along the diagonal 22 or 21 of the plate 2. In the second case (illustration 59, 60 in FIG

Motors using the voltages U1 and U2 both at the same time

Generators 24 and 23 energized. Each of the generators 24 and 23 generates in the actuator 1 a diagonal acoustic standing wave which propagates along its diagonal 22 or 21 of the plate 2. In this case, the operating regime of the engine corresponds to the connection diagram shown in FIG. 55 in FIG. In Fig. 8, the parts 27, 28 and 25, 25 of the

controlled generators 24 and 23 hatched for both connection schemes marked.

The representations 61 and 62 of FIG. 9 show the calculated or

simulated maximum deformation of the actuator 1, when it is generated in a diagonal acoustic standing wave, which propagates along the diagonal 22 of the piezoelectric plate 2. At the same time the wave becomes generated by the generator 24. The points 63 and 64 shown on the working surfaces of the friction elements 3 of the actuator 1 cooperate in the sense of a frictional connection with the friction surface 6 of the element 7 to be driven.

In a generated by the voltage U1 and along the diagonal 22 (representation 52 in Fig. 7) extending diagonal acoustic standing wave move the material points 63 and 64 of

Working surfaces of the friction elements 3 on the elliptical

Trajectories 65 and 66, shown in Fig. 10. The respective

Direction of movement is indicated by arrows. Since in the excitation of the generator 24, the part used by the generator 23 of the

piezoelectric plate 2 is not electrically activated (see illustration 58, Fig. 8), the plate 2 is asymmetrically loaded by this part. Such a load on the plate 2 leads to compensation in the

Movement paths 65 and 66, shown in Fig. 10. Under compensation of the movement paths 65 and 66 is understood that the

Dimensions of the elliptical trajectories 65 and 66 for their respective two diameters and inclination angle of

Trajectories 65 and 66 in relation to the friction layer 6 are practically equal.

The movement of all material points of the working surfaces of the

Friction elements 3 on the elliptical trajectories leads to the emergence of the force F, which acts on the part of the actuator 1 to be driven element 7 and this set in motion. Upon actuation of the changeover switch 54, the voltage U1 energizes the generator 23, whereby in the actuator 1 a along the diagonal 21 propagating acoustic

Standing wave is generated. In such a wave, the

Movement direction of the material points of the surface of the

Friction elements 3 in the opposite direction. This leads to the reversal of the direction of movement of the element to be driven in the direction shown by the arrow.

With simultaneous control of the generator 24 by the voltage U1 and the generator 23 by the additional voltage U2 or the Generator 23 by the voltage U1 and the generator 24 by the additional voltage U2 same circular movement paths 67 of the material points of the friction elements 3 can be realized. This can be done by selecting the appropriate amplitude and phase of the

Voltage U2 can be achieved. In this case, the direction of movement of the driven element 7 by reversing the

Phase shift angle between the voltages U2 and U1 are changed.

FIG. 11 shows a further embodiment of an ultrasonic motor according to the invention, in which the ultrasonic actuator 1 has two additional ones

Friction elements 68 and an additional driven element 70 with the friction layer 69 contains.

[0044] List of Reference Numerals:

1: Ultrasonic actuator

2: piezoelectric plate

3: friction element

4: housing

5: holder

6: Friction layer

7: element to be driven

8: ball bearings

9: side surface

10: face

1 1: Main area

12,13,14,15: Diagonal sections

16: middle lines

21, 22: Diagonal

23, 24: generators of diagonal acoustic standing waves

25, 26: parts of the generator 23 driven in antiphase

27, 28: parts of the generator 24 driven in antiphase

29: layer of the common electrode

30: layer of the excitation electrode of the generator 23

31: layer of the exciter electrode of the generator 24 : Piezoceramic layer

: Output of the common electrode 29: output of the excitation electrode 30

: Output of the excitation electrode 31

: electrical excitation device

: Switch

: Phase and / or voltage control unit

Claims

claims

Claim 1. Ultrasonic motor comprising an ultrasonic actuator (1) in the form of a rectangular piezoelectric plate (2), an electrical excitation device (53) and a driven element (7), wherein the ultrasonic actuator two generators (23, 24) for generating acoustic standing waves and at least two friction elements (3) arranged on it and intended to make contact with the element to be driven, characterized in that the ultrasonic actuator (1) is defined by two virtual planes (S1, S2) perpendicular to each other through the center lines (16) of its main surfaces ( 11), is divided into two pairs of diagonally opposite sections, each of the generators (23, 24) consisting of two antiphase operable parts (25, 26, 27, 28) each arranged in a different diagonal section, and the friction elements (3) on one of the end faces of the ultrasonic actuator or on two opposite

End faces (10) of the piezoelectric plate (2) are arranged.

Claim 2. Ultrasonic motor according to claim 1, characterized in that the piezoelectric plate (2) has the shape of a square or a

Has parallelepipeds.

Claim 3. Ultrasonic motor according to claim 1 or 2, characterized in that the generators (23, 24) of the standing acoustic waves have a three-layer or a multi-layer structure with at least one layer of exciter electrodes (30, 31), at least one layer of a common electrode or of common electrodes (29) and at least one layer of piezoelectric ceramic (32) arranged between adjacent electrode layers.

Claim 4. Ultrasonic motor according to one of the preceding claims,

characterized in that by the generators (23, 24) for acoustic standing waves in the ultrasonic actuator (1) of the ultrasonic motor diagonal acoustic standing waves can be generated, extending in the direction of one or both diagonals (21, 22) of one of the main surfaces (11) of the piezoelectric plate (2).

Claim 5. Ultrasonic motor according to one of the preceding claims,

characterized in that the electrical excitation device (53) of the ultrasonic actuator (1) has a changeover switch (54) for connecting one or the other generator (23, 24) for acoustic waves with the controlled by the electrical voltage ultrasonic actuator (1).

Claim 6. Ultrasonic motor according to one of claims 1 to 4, characterized

in that the electrical excitation device (53) has a block which generates an additional electrical voltage for exciting the second acoustic wave generator.

Claim 7. Ultrasonic motor according to claim 6, characterized in that the block changes the phase of the additional electrical voltage in relation to the phase of the primary electric voltage.

Claim 8. Ultrasonic motor according to claim 6 or 7, characterized in that the block changes the amplitude of the electrical additional voltage.