Ultrasonic Actuator

Abstract

The present invention relates to an ultrasonic actuator in the form of a ring or a hollow cylinder, wherein n≥2 friction elements are arranged at the end surface thereof, and 2n excitation electrodes separated from each other by separation gaps are arranged at the outer circumference thereof, and each of the friction elements is arranged in the region of the separation gap, wherein two excitation electrodes are arranged between two friction elements adjacent to the circumference of the ultrasonic actuator and located on different end surfaces, so that when the ultrasonic actuator is electrically excited, the friction elements at the two end surfaces simultaneously perform a movement, and the movement is suitable for driving the driven element to rotate in the same direction. The present invention also relates to an ultrasonic motor having such an ultrasonic actuator and a holding device, in which the ultrasonic actuator is inserted.

Description

Technical Field

[0001] The present invention relates to an ultrasonic actuator according to claims 1 to 8 and an ultrasonic motor having such an ultrasonic actuator, and a holding device for holding the ultrasonic actuator according to claims 9 and 10. Background Art

[0002] DE102013224569B3 discloses a hollow cylindrical ultrasonic actuator, wherein friction elements are arranged on the upper end face and the lower end face thereof so that the friction elements are arranged not opposite to each other but staggered at a certain circumferential angle. Here, by applying voltage to electrodes arranged on the circumferential surface of the hollow cylinder, the friction elements can be moved independently from the upper end face and the lower end face, so that two elements to be driven by the ultrasonic actuator and in contact with the corresponding friction elements can move independently from each other.

[0003] DE 10 2017 114 667 B3 teaches a hollow cylindrical ultrasonic actuator, wherein friction elements arranged at the upper end surface and the lower end surface thereof are opposite to each other.

[0004] EP2845305B1 discloses an ultrasonic actuator in the form of a hollow cylinder, wherein friction elements are arranged on one or both of its end faces. In the case of friction elements on both end faces, the same number of friction elements are arranged on each end face, wherein the position of the friction elements on one end face relative to the circumference coincides with the position of the friction elements on the other end face relative to the circumference, so that the two friction elements are arranged opposite to each other on different end faces.

[0005] By arranging the friction elements on two end faces, these friction elements can be used simultaneously to drive the driven element. To this end, the friction element of the corresponding end face contacts the associated friction element, which in turn is connected to the shaft to be driven. In order to transmit sufficient driving force from the friction element to the associated friction element, the associated friction element is pressed against the friction element of the corresponding end face.

[0006] However, a disadvantage here is that the pressure acting on the ultrasonic actuator from both sides via the friction element leads to a reduction in the deformation caused by the electrical excitation in the ultrasonic actuator, which results in a reduction in the drive power of the corresponding ultrasonic motor.

[0007] Another disadvantage of the ultrasonic actuator known from EP 2 845 305 B1 is the formation of an unfavorable impedance spectrum, especially when a greater number of friction elements are used. In other words, a greater number of friction elements arranged at the end face causes a plurality of peaks to form in the impedance spectrum near the resonance frequency of the ultrasonic actuator, which results in the vibration or movement of the friction elements being asynchronous at the operating frequency and generating undesirable noise when operating the corresponding ultrasonic motor. Summary of the invention

[0008] Therefore, the object of the present invention is to provide an ultrasonic actuator in the form of a ring or a hollow cylinder, which can generate simultaneous or synchronous movement of friction elements arranged on two end faces, which movement is suitable for driving an element to be driven, which movement is only slightly weakened by external pressure acting on the friction elements or the ultrasonic actuator, and the ultrasonic actuator has a favorable impedance spectrum, especially when a larger number of friction elements are arranged on the ultrasonic actuator, so that no undesirable noise will occur in the corresponding ultrasonic motor when the ultrasonic actuator is operated.

[0009] This object is achieved by an ultrasonic actuator according to claim 1 , wherein the subsequent dependent claims describe at least advantageous developments.

[0010] The terms occasionally used in the following parts of the description, which essentially relate to the specification of geometric data such as angles, dimensions, positions, orientations or directions, are to be understood such that the corresponding geometric data may have a deviation of + / - 5% compared to the corresponding given geometric data, wherein the deviation is, for example, due to manufacturing tolerances or installation tolerances.

[0011] The ultrasonic actuator according to the invention is made of an electromechanical material, and preferably of a piezoelectric material such as a piezoelectric ceramic (e.g. PZT). In addition, the ultrasonic actuator can also be made of an electrostrictive or magnetostrictive material. The ultrasonic actuator has a ring form or a hollow cylindrical form, and has an inner peripheral surface pointing radially inward and an outer peripheral surface pointing radially outward, a single common electrode being arranged at the inner peripheral surface, wherein the inner peripheral surface and the outer peripheral surface are connected to each other via two end surfaces. At each of the two end surfaces, at least one friction element in the form of a hemisphere, for example made of an oxide ceramic such as Al2O3, is arranged, so that at least n≥2 friction elements are arranged together at the two end surfaces. Other geometric shapes of the friction elements can also be envisaged.

[0012] 2n excitation electrodes are arranged on the outer circumferential surface of the ultrasonic actuator, wherein adjacent excitation electrodes are spaced apart from each other by separation gaps and are electrically insulated from each other by the separation gaps.

[0013] By applying a suitable voltage to the electrodes of the ultrasonic actuator or by applying multiple suitable voltages to the electrodes of the ultrasonic actuator, the electromechanical material can be excited to form periodic deformation, and the periodic deformation is transmitted to the friction element arranged on the ultrasonic actuator, wherein the corresponding movement path of the friction element can be used to drive one or more elements to be driven that are in contact with the friction element.

[0014] Here, each of the friction elements is arranged at a corresponding end surface in the region of the separation gap, wherein two excitation electrodes are arranged between friction elements that are adjacent to each other but located on different end surfaces relative to the circumference of the ultrasonic actuator, and a separation gap exists between the two excitation electrodes. These friction elements that are adjacent to each other but arranged on different end surfaces form opposing paired friction elements.

[0015] When the ultrasonic actuator is electrically excited, i.e., when one or more voltages are applied to the electrodes of the ultrasonic actuator, all friction elements arranged on the ultrasonic actuator, i.e., all friction elements arranged at one end surface and all friction elements arranged at another opposite end surface, perform a simultaneous or synchronous movement suitable for the same-direction rotational drive of the elements to be driven that are in contact with the friction elements. In other words, all friction elements vibrate so that the elements to be driven are driven in the same rotational direction due to their vibration paths.

[0016] It may be advantageous if the distance between the two friction elements of a opposing pair relative to the circumference of the ultrasonic actuator is the same for all pairs, so that two adjacent pairs of friction elements are arranged symmetrically to one another.

[0017] It may also be advantageous that both of the two end surfaces have recesses in the region of the separation gap between the two opposing paired excitation electrodes. It may be particularly advantageous that the recesses are arranged to be evenly distributed on the circumference of the ultrasonic actuator.

[0018] It may also be advantageous if the recess is groove-shaped and has, in particular, a substantially V-shape or U-shape in cross section.

[0019] It may also be advantageous if the groove-shaped recess has a radial orientation.

[0020] It may be advantageous if the excitation electrode has a shape having more than four corners and in particular an octagonal shape.

[0021] The present invention also relates to an ultrasonic motor having the aforementioned ultrasonic actuator and a holding device, wherein the ultrasonic actuator is inserted into the holding device. The holding device has an inner contact element, an outer contact element and two holding elements.

[0022] The inner contact element and the outer contact element are connected to each other through the two holding elements, wherein the inner contact element is in section contact with the inner peripheral surface of the ultrasonic actuator through a protruding portion, and the outer contact element is in section contact with the outer peripheral surface of the ultrasonic actuator through a protruding portion. In addition, the holding elements are in direct or indirect contact with the end surface of the ultrasonic actuator, wherein the holding elements clamp the ultrasonic actuator in the middle. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] The advantages and utility of the present invention will become more apparent from the following description of preferred embodiments with reference to the accompanying drawings. In the drawings:

[0024] Figure 1 and Figure 2 An embodiment of an ultrasonic actuator according to the present invention is shown;

[0025] Figure 3a and Figure 3b The expanded diagram shows the Figure 1 and Figure 2 Ultrasonic actuators;

[0026] Figure 4 a and Figure 4 b shows two other embodiments of the ultrasonic actuator according to the present invention;

[0027] Figure 5 a to Figure 5 d shows another embodiment of the ultrasonic actuator according to the present invention in different views;

[0028] Figure 6 An embodiment of an ultrasonic actuator having an octagonal excitation electrode according to the present invention is shown;

[0029] Figure 7 A holding device having an ultrasonic actuator mounted therein is shown;

[0030] Figure 8 The exploded diagram shows the Figure 7 A holding device and an ultrasonic actuator;

[0031] Fig. 9 Shows that according to Figure 1 and Figure 2 The ultrasonic actuator according to the present invention and the Figure 7 or Figure 8 The holding device of the ultrasonic motor. DETAILED DESCRIPTION

[0032] according to Figure 1 and Figure 2 The ultrasonic actuator 1 according to the present invention has a hollow cylindrical shape, wherein a single common electrode 7 is arranged on the inner peripheral surface (2) pointing radially inward, and the single common electrode 7 almost completely covers the inner peripheral surface 2. Twelve excitation electrodes 8 in a substantially square shape are arranged on the outer peripheral surface 3 pointing radially outward and evenly distributed on the circumference of the hollow cylinder, wherein adjacent excitation electrodes are separated from each other by separation gaps 9 and are electrically insulated from each other by the separation gaps 9. Figure 1 and Figure 2 The excitation electrodes 8 shown with hatching in FIG. 8 are shown with hatching only for reasons of illustration and clarity, but in other respects they are identical to the excitation electrodes 8 not shown with hatching.

[0033] The inner circumference 2 and the outer circumference 3 are connected to each other by two flat end faces 4 and 5 arranged opposite to each other. It is conceivable that one of the two end faces is not flat but has an inclination, or that both end faces are not flat but have an inclination. In other words, it is conceivable that the ultrasonic actuator according to the present invention is Figure 1 and Figure 2 Unlike the embodiment shown in , one or both end surfaces 4 and 5 are not arranged at right angles to the inner circumference 2 and the outer circumference 3 .

[0034] On each of the two end faces 4 and 5, three hemispherical friction elements 6 made of Al2O3 are arranged evenly distributed on the circumference, wherein these friction elements 6 are connected to the piezoelectric ceramic material of the ultrasonic actuator in a material-fitting manner. However, it is also conceivable that the friction elements 6 are arranged at the end faces by a form-fitting connection, for example by embedding or inserting the spherical friction elements into complementary recesses at the end faces.

[0035] The ultrasonic actuator comprises a total of six friction elements 6. Each friction element 6 is arranged in the region of a separation gap 9 between adjacent excitation electrodes 8.

[0036] Two excitation electrodes 8 are arranged between two friction elements 6 adjacent to each other but located on different end faces 4, 5 relative to the circumference of the ultrasonic actuator 1. In this case, the corresponding friction elements 6 adjacent to each other and located on different end faces 4, 5 relative to the circumference of the ultrasonic actuator 1 form a matching pair 10, such as Figure 2 shown.

[0037] The distance between the two friction elements 6 of a mating pair 10 relative to the circumference of the ultrasonic actuator 1 is the same for all two mating pairs 10 , so that two adjacent mating pairs 10 of friction elements 6 are arranged symmetrically to one another relative to the circumference.

[0038] The two end faces 4 and 5 each have a groove-shaped recess 11 in the region of the separation gap 9 between the two excitation electrodes 8 of a mating pair 10, so that in the present case each of the two end faces 4 and 5 comprises six recesses 11 evenly distributed over the circumference, wherein Figure 1 and Figure 2 The six recesses 11 on the upper end surface 4 are in contact with Figure 1 and Figure 2 The six recesses 11 of the lower end surface 5 are arranged at the same circumferential position. In other words, the recesses 11 are arranged in pairs opposite to each other. Here, all the groove-shaped recesses 11 are arranged substantially perpendicular to the inner circumferential surface 2 and perpendicular to the outer circumferential surface 3.

[0039] This specific arrangement of the friction elements 6 and the excitation electrodes 8 relative to each other enables the friction elements 6 of the two end faces 4 and 5, i.e., all the friction elements of the ultrasonic actuator 1, to perform simultaneous or synchronous movement when the ultrasonic actuator 1 is electrically excited, i.e., when one or more voltages are applied to the electrodes 7 and 8, which results in rotational drive of the element to be driven that is in contact with the friction elements.

[0040] The above content can be found in particular in Figure 3a and Figure 3b These figures show in expanded form the Figure 1 and Figure 2 This diagram is better suited to showing how all friction elements 6 arranged at the two end faces 4 and 5 move under suitable electrical control of the ultrasonic actuator according to the invention. Figure 3a and Figure 3b The only difference is the opposite vibration direction of the friction element 6, which leads to the opposite rotational movement of the element to be driven in contact with the friction element 6 (in Figure 3a and Figure 3b (not shown). Figure 3a and Figure 3b Not shown in Figure 1 and Figure 2 The recessed portion 11 of the ultrasonic actuator is shown in order to keep the illustration as simple as possible.

[0041] from Figure 3aIt can be seen in FIG. 1 that when the excitation electrode 8 shown by the hatching of the ultrasonic actuator 1 is appropriately electrically controlled, the three friction elements 6 arranged at the upper end face 4 move in the same direction and synchronously in an oscillating motion path or trajectory that is inclined to the end face 4 and is substantially linear, as indicated by the double arrows shown. At the same time, the three friction elements 6 arranged at the lower end face 5 move in the same direction and synchronously in an oscillating motion path or trajectory that is inclined to the end face 5 and is substantially linear, wherein the motion path or trajectory is arranged to be substantially opposite to the trajectory of the friction elements 6 arranged at the end face 4 (also indicated by the double arrows shown). In other words, the trajectory of the friction elements arranged at the upper end face 4 encloses a smaller and a larger angle with the end face 4, and the two angles are substantially the same as the corresponding angles enclosed by the trajectory of the friction elements 6 arranged at the lower end face 5 with the end face 5.

[0042] By means of the friction elements 6 arranged on the two end faces 4 and 5 Figure 3a The trajectory shown can generate a driven element (at Figure 3a and Figure 3b In contrast, the friction elements 6 arranged on the two end faces 4 and 5 can be used to achieve a rotational movement in the counterclockwise direction. Figure 3b The excitation electrode 8 shown by the hatched line is appropriately electrically controlled to generate Figure 3b The opposite trajectory shown in generates a movement of the element to be driven in contact with the friction element 6 which corresponds to a clockwise rotational movement.

[0043] and Figure 3a and Figure 3b Different from the linear trajectory indicated by the double arrows in the figure, an elliptical or circular trajectory is also suitable.

[0044] Figure 4 Figure 1 shows an embodiment of an ultrasonic actuator 1 according to the present invention, in which only one friction element 6 is arranged on each of the two end faces 4 and 5. Here, the friction elements 6 are arranged diametrically opposite to each other, that is, there is an angular distance of substantially 180° between the two friction elements relative to the circumference of the hollow cylinder. The ultrasonic actuator also has four identical excitation electrodes 8 uniformly arranged on the outer circumference of the hollow cylinder and each separated from each other by a separation gap 9. Each of the two end faces 4 and 5 has two groove-shaped recesses 11 arranged diametrically opposite to each other and positioned identically relative to the circumference of the hollow cylinder.

[0045] exist Figure 4 Another embodiment of the ultrasonic actuator according to the present invention is shown in FIG. Figure 4Unlike the ultrasonic actuator shown in a, each end face is provided with two friction elements 6 arranged radially opposite to each other. The angular distance between adjacent friction elements arranged on different end faces relative to the circumference of the hollow cylinder is substantially 90°. A total of eight identical excitation electrodes 8 are arranged on the outer circumferential surface 3 of the ultrasonic actuator 1. Each of the end faces 3 and 4 has four groove-shaped recesses 11 evenly distributed on the circumference.

[0046] Figure 5 Another embodiment of an ultrasonic actuator 1 according to the invention is shown in different views in FIGS. (a) to (d), wherein: Figure 5 (a) shows an ultrasonic actuator in a stereoscopic view, Figure 5 (b) shows a top view from the bottom or in the direction of the end face 5, Figure 5 (c) shows a side view, and Figure 5 (d) shows a top view of the upper side or the direction toward the upper end face 4. In this ultrasonic actuator, different numbers of friction elements 6 are arranged on the two end faces 4 and 5. Figure 5 In the figure, three friction elements 6 are arranged on the upper end face 4 and are unevenly distributed on the circumference. In the figure, only two friction elements 6 are arranged on the lower end face 5, which are not arranged radially opposite to each other, so that there is also an uneven distribution of the friction elements 6 on the circumference of the end face 5. This results in a total of four matching pairs 10 of friction elements 6. Ten identical excitation electrodes 8 that are spaced apart from each other are arranged on the outer circumference 3 of the hollow cylindrical ultrasonic actuator 1.

[0047] Figure 6 Another embodiment of the ultrasonic actuator 1 according to the present invention is shown. Figure 1 and Figure 2 The embodiment shown is different and has an octagonal excitation electrode 8. Due to this shape of the excitation electrode 8, in particular the area of ​​the electromechanical material of the hollow cylindrical ring remains free and not covered with the electrode, and the vibration amplitude of the ultrasonic actuator that is excited to apply the periodic deformation is relatively large. The ultrasonic actuator designed in this way requires less electrical energy and can therefore be operated more efficiently. In addition Figure 6 In addition to the octagonal shape of the excitation electrodes shown, other shapes are also conceivable, in which the end region between two adjacent excitation electrodes facing the respective end face remains uncovered by the electrode. For this purpose, for example, round or rounded excitation electrodes or oval excitation electrodes are also suitable.

[0048] and Figure 1 and Figure 2 Compared with the embodiment shown, the only other distinguishing feature is the recesses at the end faces 4 and 5, which are formed according to Figure 6 It does not exist in ultrasonic actuators.

[0049] Figure 7 and Figure 8 The holding device 12 for the ultrasonic actuator according to the invention is shown in different illustrations, wherein in this case, according to Figure 1 and Figure 2 The ultrasonic actuator is mounted or inserted in the holding device. The holding device 12 has an inner contact element 13, an outer contact element 14 and two folding elements 15 and 16. Here, the inner and outer contact elements 13 and 14 are made of plastic, preferably polyetheretherketone (PEEK), while the two holding elements 15 and 16 are made of metal with elastic properties, preferably spring steel.

[0050] The substantially hollow cylindrical internal contact element 13 partially contacts the inner circumference of the ultrasonic actuator 1 through protrusions 22 evenly distributed on the circumference, while the substantially hollow cylindrical external contact element surrounding the ultrasonic actuator at its outer circumference partially contacts the outer circumference of the ultrasonic actuator through protrusions 23. The protrusions 22 and 23 of the internal and external contact elements 13 and 14 contact the ultrasonic actuator at the position or area of ​​the vibration node of the ultrasonic actuator that undergoes periodic deformation during operation.

[0051] The ultrasonic actuator 1 is already supported or held by the projections 22 and 23 of the inner and outer contact elements 13 and 14 in such a way that lateral displacement of the ultrasonic actuator in a plane is largely prohibited. However, in order to also additionally protect the ultrasonic actuator against rotational displacement and in particular against axial displacement, the inner contact element 13 and the outer contact element 14 are connected to each other by two holding elements 15 and 16 arranged parallel to each other and constructed identically. The holding elements 15 and 16 here have two essentially circular annular parts 17 and 18 arranged concentrically to each other and a web part 19 connecting the annular parts 17 and 18 to each other.

[0052] Figure 7 The upper holding element 15 is arranged to face the end surface 4 of the ultrasonic actuator or close to the end surface 4, and Figure 7 The lower holding element 16 in the embodiment faces the end face 5 of the ultrasonic actuator. The holding elements 15 and 16 are connected to the inner and outer contact elements 13 and 14 by means of fastening means 21 in the form of screws, wherein the inner annular portion 17 is screwed to the inner contact element 13 at a plurality of positions evenly distributed on the circumference, and the outer annular portion 18 is screwed to the outer contact element 14 at a plurality of positions evenly distributed on the circumference.

[0053] The web portion 19 connecting the inner annular portion 17 and the outer annular portion 18 to each other indirectly contacts the respectively assigned end face 4 or 5 via an intermediate element 20 made of a rubber-like material. On the one hand, the intermediate element 20 prevents the holding elements 15 and 16 made of metal from directly contacting the electromechanical material of the ultrasonic actuator, which would lead to wear of the electromechanical material due to the vibration of the ultrasonic actuator. On the other hand, the rubber-like material of the intermediate element 20 provides a relatively high friction coefficient for the pairing between the intermediate element / web portion of the holding element and the intermediate element / end face of the ultrasonic actuator, thereby effectively coping with attempts to make the ultrasonic actuator perform rotational movement or displacement.

[0054] The intermediate element 20 includes an annular portion 201 and a plurality of lug portions 202 integrally formed with the annular portion 201 , wherein the lug portions 202 are evenly distributed on the circumference of the annular portion 201 and are arranged in a radial orientation.

[0055] The web parts 19 of the two retaining elements 15 and 16 are arranged so that they are located substantially in the same position as in the Figure 7 Here, the width of the web portion 19 is smaller than the width of the recess 11, so that the corresponding part of the deformable intermediate element 20 is at least partially pressed into the corresponding recess 11 through the web portion 19, and the resulting mechanical intervention compensates the rotational displacement of the ultrasonic actuator during operation in an optimal manner.

[0056] The intermediate element 20 also ensures that a sufficient retaining force or compression force can be applied to the ultrasonic actuator via the corresponding web portion 20 in the axial direction, i.e. in the direction of the corresponding end face of the ultrasonic actuator, since even in the case of small manufacturing tolerances, the contact between the corresponding web portion 19 and the associated end F9 face 4 or 5 of the ultrasonic actuator 1 is ensured by the intermediate element.

[0057] Figure 8 The exploded diagram shows the Figure 7 The various parts of the arrangement of the holding device and the ultrasonic actuator. In particular, it can be Figure 8 The intermediate element 20 can be seen in FIG. 1 , which is an integral or one-piece construction and has an annular portion 201 and lug portions 202 which are evenly distributed over the circumference of the annular portion and extend away from the annular portion 201 in the radial direction.

[0058] Reference Figure 8It is also possible to see better the projections 22 of the inner contact element 13 and the projections 23 of the outer contact element 14. The projections 22 and 23 are each evenly distributed over the circumference, wherein the inner contact element 13 has six projections 22 formed integrally therewith and pointing radially outwards, and the outer contact element 14 has twelve projections 23 formed integrally therewith and pointing radially inwards.

[0059] Fig. 9 Shows that according to Figure 1 and Figure 2 The ultrasonic motor of the ultrasonic actuator 1 according to the present invention is inserted into the Figure 7 and Figure 8 In the retaining device 12 according to the present invention, the friction ring 104 is in contact with the friction element 6 on the end surface and is pressed against the corresponding friction element 6 through the spring washer 106.

[0060] The holding device 12 is fixedly connected to the housing 102 of the ultrasonic motor 100, while the spring washer 106 is connected to a section of a drive shaft 108 of the ultrasonic motor 100. The drive shaft 108 is rotatably supported relative to the housing 102 via a bearing element 110 in the form of a ball bearing.

[0061] During operation of the ultrasonic motor 100, the periodic movement of the friction elements 6 arranged at the two end faces of the ultrasonic actuator 1 causes the two friction rings 104 to be driven in the same direction, and the movement is transmitted to the drive shaft 108 through the fixed connection between the friction ring 104 and the spring washer 106 and the simultaneous fixed connection between the spring washer 106 and the drive shaft 108, thereby realizing the rotational drive of the drive shaft 108.

[0062] Description of reference numerals:

[0063] 1 Ultrasonic Actuator

[0064] 2 Inner circumference (of ultrasonic actuator 1)

[0065] 3 Outer peripheral surface (of ultrasonic actuator 1)

[0066] 4, 5 End surface (of ultrasonic actuator 1)

[0067] 6 Friction element

[0068] 7 Common electrode

[0069] 8 Excitation electrodes

[0070] 9 Separation gap

[0071] 10 (friction element 6) matching pair

[0072] 11 Recessed portion (of ultrasonic actuator 1)

[0073] 12. Holding device

[0074] 13 Internal contact element (of holding device 12)

[0075] 14 External contact element (of the holding device 12)

[0076] 15, 16 Retaining element (of the retaining device 12)

[0077] 17 Inner annular portion (of retaining elements 15, 16)

[0078] 18 Outer annular portion (of retaining elements 15, 16)

[0079] 19 Web portion (of retaining elements 15, 16)

[0080] 20 Intermediate components

[0081] 21 Fastening device

[0082] 22 protruding portion (of the internal contact element 13)

[0083] 23 Projecting portion (of external contact element 14)

[0084] 100 Ultrasonic motor

[0085] 102 Housing (of ultrasonic motor 100)

[0086] 104 Friction ring (of ultrasonic motor 100)

[0087] 106 Spring washer (of ultrasonic motor 100)

[0088] 108 (Drive shaft of ultrasonic motor 100)

[0089] 110 Bearing element (of ultrasonic motor 100)

[0090] 201 annular portion (of the intermediate element 20)

[0091] 202 Lug portion (of the intermediate element 20)

Claims

1. An ultrasonic actuator (1) in the form of a ring or a hollow cylinder made of an electromechanical material, comprising: an inner peripheral surface (2) pointing radially inward, an outer peripheral surface (3) pointing radially outward, and two end surfaces (4, 5) connecting the inner peripheral surface and the outer peripheral surface, wherein at least one friction element (6) is arranged on each of the two end surfaces (4, 5), so that the ultrasonic actuator (1) includes a total of n friction elements (6), wherein n ≥ 2, and a common electrode (7) is arranged at the inner peripheral surface (2), and 2n excitation electrodes (8) are arranged on the outer peripheral surface (3), in, Adjacent excitation electrodes (8) are separated from each other by a separation gap (9), and each friction element (6) is arranged in the area of ​​the separation gap (9), wherein two excitation electrodes (8) are arranged between two friction elements (6) that are adjacent to the circumference of the ultrasonic actuator (1) and located on different end faces (4, 5) to form a matching pair (10), and when the ultrasonic actuator (1) is electrically excited, the friction elements (6) on the two end faces (4, 5) simultaneously perform movement, and the movement is suitable for the same-direction rotational drive of the element to be driven that is in contact with the friction element.

2. The ultrasonic actuator (1) according to claim 1, It is characterized in that For all mating pairs (10), the distance between the two friction elements (6) of the mating pair (10) relative to the circumference of the ultrasonic actuator (2) is the same, so that two adjacent mating pairs (10) of friction elements (6) are arranged symmetrically to each other.

3. The ultrasonic actuator (1) according to claim 1, It is characterized in that The two end faces (4, 5) each have a recess (11) in the region of the separation gap (9) between the two excitation electrodes (8) of a mating pair (10).

4. The ultrasonic actuator (1) according to claim 3, It is characterized in that The recesses (11) are arranged to be evenly distributed on the circumference of the ultrasonic actuator (1).

5. The ultrasonic actuator (1) according to claim 3, It is characterized in that The recess (11) is groove-shaped.

6. The ultrasonic actuator (1) according to claim 5, It is characterized in that The groove-shaped recess (1) has a substantially V-shaped or U-shaped cross section.

7. The ultrasonic actuator (1) according to claim 5, It is characterized in that The groove-shaped recess (11) is arranged substantially perpendicular to the inner peripheral surface (2) and perpendicular to the outer peripheral surface (3).

8. The ultrasonic actuator (1) according to claim 1, It is characterized in that The excitation electrode (8) has a shape having more than four corners.

9. The ultrasonic actuator (1) according to claim 8, It is characterized in that The excitation electrode (8) has an octagonal shape.

10. An ultrasonic motor (100) comprising an ultrasonic actuator (1) according to any one of claims 1 to 9 and a holding device (12), in, The ultrasonic motor is inserted into the holding device, and the holding device (12) has an inner contact element (13), an outer contact element (14), two holding elements (15, 16) and two intermediate elements (20), wherein the retaining element (15, 16) comprises two substantially circular annular portions (17, 18) arranged concentrically with each other and a web portion (19) connecting the annular portions (17, 18) to each other, wherein the intermediate element (20) comprises an annular portion (201) and a plurality of lug portions (202) integrally formed with the annular portion (201), wherein the lug portions (202) are evenly distributed on the circumference of the annular portion (201) and are arranged in a radial orientation, wherein the web portions (19) of the two retaining elements (15, 16) are arranged such that their positions substantially coincide with the positions of the recesses (11) of the ultrasonic actuator, wherein the width of the web portion (19) is smaller than the width of the recesses (11), so that the corresponding portion of the deformable intermediate element (20) is at least partially pressed into the corresponding recess (11) by the web portion (19), and the mechanical intervention thus produced counteracts the rotational displacement of the ultrasonic actuator during operation in an optimized manner, The internal contact element (13) and the external contact element (14) are connected to each other via the two retaining elements (15, 16), and the internal contact element (13) is partially in contact with the inner peripheral surface (2) of the ultrasonic actuator (1), and the external contact element (14) is partially in contact with the outer peripheral surface (3) of the ultrasonic actuator (1), and furthermore, the retaining elements (15, 16) are in contact with the end surfaces (4, 5) of the ultrasonic actuator (1) and clamp the ultrasonic actuator (1) in the middle.

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