Ultrasonic actuator and motor having the same

Abstract

The invention relates to an ultrasonic actuator (1) in the form of a plate (2), comprising a base (3), a cover surface (4) geometrically similar to the base, and a side surface (5) connecting the base and the cover surface to each other, wherein the plate comprises an electromagnetic material, electrodes (6, 6', 7, 7') for exciting periodic deformation of the plate are arranged on the base of the plate and on the cover surface of the plate opposite to the base, and the base (3) comprises at least two faces (8, 8') arranged parallel to each other and forming contact portions (50, 50') of the side surface (5), and the two faces of the base arranged parallel to each other together with a connecting line (9, 9') form a parallelogram (10) inscribed in the base, the connecting line connecting the corresponding end points of the parallel faces (8, 8'), wherein the parallelogram having an angle different from 90° is enclosed between adjacent faces. The invention also relates to a motor having such an ultrasonic actuator.

Description

Technical Field

[0001] The invention relates to an ultrasonic actuator in the form of a plate having a base, a cover surface geometrically similar to the base and a side or side surfaces interconnecting the base and the cover surface, wherein the plate has an electromechanical material and electrodes are arranged on the base of the plate and on the cover surface of the plate opposite the base for exciting periodic deformations of the plate, and the base has at least two sides arranged parallel to each other, the at least two sides defining contact portions of the side surfaces, the two sides of the base surface arranged parallel to each other forming a parallelogram inscribed in the base together with a connecting line interconnecting the respective end points of these sides arranged parallel to each other, as described in the preamble to claim 1. The invention further relates to a motor having such an ultrasonic actuator forming an ultrasonic motor. Background Art

[0002] In this context, the term "electromechanical material" used above and below is to be understood as a material which undergoes mechanical deformation when a voltage is applied and a corresponding electric field is generated. In particular, this includes materials with piezoelectric properties, such as piezoelectric ceramic materials, but also materials with electrostatic properties, for example.

[0003] These ultrasonic actuators or ultrasonic motors incorporating them can be used in miniaturized, inexpensive devices with low power consumption, such as micro cameras, lenses for mobile phones or smartphones, micro storage devices, and similar devices, where small size, high positioning accuracy, and low power consumption of the drive are required.

[0004] Ultrasonic actuators for ultrasonic motors are known from US 5 672 930 and US 5 665 918, which are designed as complex composite vibrators consisting of a resonant body to which a piezoelectric excitation plate is bonded. The disadvantage of these actuators is that they have a relatively complex structure and are expensive to manufacture. Therefore, they are excluded as cheap mass-produced products for use in miniaturized devices.

[0005] Furthermore, from document US 6 765 335 B2 an ultrasonic actuator for ultrasonic motors is known, in which the resonant body is formed as a piezoelectric plate having a rectangular shape. This ultrasonic actuator is characterized by a simple design and an easily controllable manufacturing technology, which is why it appears suitable as a low-cost mass product. However, the disadvantage of this ultrasonic actuator is visible in the fact that its operation requires relatively high electrical power, resulting in increased energy consumption. Therefore, this ultrasonic actuator is also excluded from use in micro devices with correspondingly required low energy consumption.

[0006] The ultrasonic actuator known from EP 2 153 476 B1 can indeed solve the above-mentioned problems, since it has a relatively simple design, at the same time has low electrical power consumption and high operational stability or safety. However, in the case of the ultrasonic actuator disclosed in EP 2 153 476 B1, the realization of a corresponding ultrasonic motor is associated with higher costs, in particular with regard to the construction of the armature of such a motor. In this case, it proves to be relatively expensive to achieve a constant contact force of the rotor on the ultrasonic actuator over the entire travel distance of the armature, which is necessary for permanently reliable operation. Summary of the invention

[0007] The object of the present invention is therefore to provide an ultrasonic actuator which, in addition to a simple design and low electrical energy consumption, has properties which allow a simple construction and a permanently reliable motor to be realized, which can be manufactured and assembled in an easy manner, especially in large quantities, and has good scalability or miniaturization.

[0008] This object is solved by an ultrasonic actuator of the type mentioned at the outset, wherein, with respect to the parallelogram inscribed in the base, in each case between adjacent or adjacent or neighboring sides an angle deviating from 90° is included. In other words, in particular, the inscribed parallelogram is not a right-angled parallelogram.

[0009] Due to the specific shape of the inscribed parallelogram, the corresponding sides arranged parallel to each other do not completely overlap by shifting the normals along their corresponding sides, as in the case of a right-angled parallelogram. In other words, the normals that pass through the centers of the corresponding sides do not intersect, but are arranged parallel to each other and offset. In this case, if a force acts along the normal relative to the contact portion or contact surface formed by the corresponding sides of the side surface - for example, due to the running surface of the armature to be moved relative to the ultrasonic actuator being pressed against the contact portion or contact surface of the ultrasonic actuator - a torque that attempts to rotate the ultrasonic actuator is generated. The corresponding counter-torque acting on the running surface can be used to generate a defined contact force of a guide component or its guide portion, which is connected to the armature or is integral with the armature and abuts against the guide element of the guide device. In this way, the mechanical preload on the ultrasonic actuator required for the optimized operation of the corresponding ultrasonic motor and the above-mentioned contact pressure of the guide portion against the guide element (preferably a sliding guide) of the guide device can be simultaneously achieved via the running surface, which is, for example, a component of the armature.

[0010] In this respect, it may be advantageous if the larger inner angle of the inscribed parallelogram has a value between 93° and 105°, and preferably between 95° and 99°. Thus, the smaller inner angle of the inscribed parallelogram has a value between 87° and 75°, and preferably between 85° and 81°. By means of such a geometry of the inscribed parallelogram, in the case of such a corresponding ultrasonic motor in which the running surface of the armature is pressed against the contact of the ultrasonic actuator, a counter-torque which is advantageous for a permanently reliable operation of the ultrasonic motor can be applied to the guide device connected to the armature, whereas in the case of smaller values ​​of the larger inner angle, a torque or counter-torque sufficient for this purpose may no longer be achieved. At larger values ​​of the larger inner angle, less stable and less defined oscillations of the ultrasonic actuator are produced, resulting in lower positioning accuracy and less regular drive in the case of a corresponding ultrasonic motor.

[0011] It may be advantageous if the base or the covering surface arranged parallel thereto and geometrically similar (preferably identically shaped) is octagonal and that the inscribed parallelogram is adjoined on both sides by a trapezoid, preferably an isosceles trapezoid, in each case, and the base of each trapezoid coincides with the respective longer side of the inscribed parallelogram. The resulting prismatic shape of the ultrasonic actuator enables particularly efficient excitation of deformations that can be used to drive the armature with relatively low material costs.

[0012] In the case of an isosceles trapezoid, it may be advantageous if the length of the diagonal of the trapezoid is substantially equal to the distance between the side opposite the base or base of the trapezoid and the base of another trapezoid. These geometric ratios result in an ultrasonic actuator having a width less than twice its height and therefore a relatively small footprint, requiring less material. Furthermore, such geometric ratios of the ultrasonic actuator result in three dimensions being superimposed on the vibration mode used. One dimension of the vibration mode may be suppressed by external influences, but this does not lead to the disappearance of the vibration mode used. This increases the overall robustness of the motor against external influences and the mechanical environment of the actuator.

[0013] The present invention also relates to a motor having the above-mentioned ultrasonic actuator and comprising a mounting device for fixedly mounting the ultrasonic actuator and an armature that can move relative to the ultrasonic actuator and is in direct or indirect friction contact with the ultrasonic actuator, wherein the mounting device comprises at least four retaining parts that contact the ultrasonic actuator at different areas, two of which are mechanically rigid and form rigid retaining parts, and two of which have elastic properties and form elastic retaining parts.

[0014] In this case, it may be advantageous if both the rigid retaining portion and the elastic retaining portion are arranged obliquely relative to one another.

[0015] Furthermore, it may be advantageous if the mounting device comprises two further holding portions, each of which contacts an area of ​​the side surface of the ultrasonic actuator between areas of the side surface contacted by a respective rigid holding portion and a respective elastic holding portion.

[0016] In one embodiment, the motor can be configured such that the armature comprises two elongated and parallel running surfaces which directly or indirectly contact the ultrasonic actuator at the contact portion and clamp the ultrasonic actuator between them. Due to the clamping force introduced via the contact portion, a torque acts on the ultrasonic actuator due to its specific geometry, whereby the ultrasonic actuator is pressed with corresponding portions of the side surfaces against corresponding rigid retaining portions of the mounting device.

[0017] In this case, it may be advantageous if the armature comprises a guide component having at least two guide sections spaced apart from one another, which engage with a guide element or a guide section so as to enable a sliding movement. In the case of a guide element, the guide element is present separately, whereas in the case of a guide section, the guide section is preferably an integral part of the mounting device. The guide section is preferably formed integrally with the guide component, and the guide component is preferably formed integrally with the armature.

[0018] The following is a description of embodiments of an ultrasonic actuator and a corresponding motor according to the present invention with respect to corresponding drawings, wherein the same reference numerals refer to the same parts of different drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 : A top view of the base of the ultrasonic actuator according to the present invention.

[0020] Figure 2A , Figure 2B :according to Figure 1 Different perspective views of an ultrasonic actuator.

[0021] Figure 3 : Based on Figure 1 and a perspective view of an embodiment of a motor of an ultrasonic actuator of FIG. 2 .

[0022] Figure 4 :Used according to Figure 3 The motor of the ultrasonic actuator is mounted on the device.

[0023] Figure 5 :according to Figure 3 Side view of the motor.

[0024] Figure 6 : Based on Figure 1 and a perspective view of an embodiment of a motor of an ultrasonic actuator of FIG. 2 . DETAILED DESCRIPTION

[0025] Figure 1 The base 3 of the ultrasonic actuator 1 according to the present invention is shown in a plan view. The base 3 has the shape of an octagonal plate 2 or an octagonal prism, so that the base 3 is opposite to the base 3 and Figure 1 The cover surface not visible in the figure has the same shape as the base 3, and the side surface 5 connecting the base 3 and the cover surface to each other is arranged perpendicular to both the base 3 and the cover surface. However, embodiments of the ultrasonic actuator 1 are also conceivable, in which the shape of the base 3 and the cover surface are different from each other but have geometrical similarities, so that the side surface 5 is not arranged perpendicular to the base 3 or the cover surface.

[0026] The octagonal shape of the base 3 and the corresponding prismatic shape of the ultrasonic actuator result in a side surface 5 having eight sections distinguishable from one another, wherein the side edges 8 and 8' form contact portions 50 and 50' of the side surface 5. The contact portions 50 and 50' are provided for direct or indirect contact with an element of a corresponding ultrasonic motor to be driven by the ultrasonic actuator.

[0027] The two shorter sides of the base 3 (i.e., the sides 8 and 8') are arranged parallel to each other and spaced apart from each other, and by moving the sides along their respective side normals, the sides 8 and 8' cannot completely overlap. In other words, the sides 8 and 8' (as seen in their extension direction) are arranged to be offset from each other. In a corresponding manner, two connecting lines 9 and 9' that connect the corresponding end points of the sides 8 and 8' respectively to each other produce a parallelogram 10 inscribed in the base 3, which is not rectangular or in which adjacent or adjoining sides enclose an angle between them that deviates from 90°. In this case, the two larger angles 11 of the parallelogram are 97°, resulting in a smaller angle of the parallelogram of 83°.

[0028] On both sides of the inscribed parallelogram 10, relative to the base 3, adjoin respective isosceles trapezoids 12, 12', the respective bases 13, 13' of which coincide with the respective long sides of the inscribed parallelogram 10, which correspond to the respective connecting lines 9, 9'. The length of each diagonal 14 of a trapezoid 12, 12' is substantially equal to the shortest distance 15 between the side 16, 16' of the trapezoid opposite the base 13, 13' and the base 13, 13' of the respective other trapezoid 12, 12'. In the present case, the sides 16, 16', which also represent the shorter sides of the shape of the base 3, are arranged parallel to the bases 13, 13' of the respective trapezoid 12, 12'.

[0029] Due to the fact that the inscribed parallelogram 10 is not a right parallelogram, side normals extending from the center points of the sides 16, 16' opposite and parallel to the bases 13, 13' of the respective right trapezoids do not intersect but extend parallel and spaced apart from each other.

[0030] Figure 2A The perspective view mainly pointing to the base 3 shows the Figure 1 Ultrasonic actuator 1. Two identically formed electrodes 6 and 6' arranged in a mirror image of each other are located on an octagonal base 3 and are separated from each other by an intermediate gap and are electrically insulated from each other. In addition to the contact portions 50 and 50' formed by the side edges 8 and 8' of the base 3, the longer sides of the base 3 form parts 52, 52', 54 and 54' of the side surface 5, and the two remaining shorter sides 16 and 16' of the base 3 form or define parts 56 and 56' of the side surface 5.

[0031] Figure 2B Shown in different perspectives Figure 1 , so that mainly the cover surface 4 can be seen here. Just as on the base 3, two mirror-image electrodes 7 and 7' of identical shape are located on the cover surface 4, which are also spaced apart from each other by a separation gap in between and are therefore electrically insulated from each other. The two electrodes 7 and 7' of the cover surface are arranged mirror-image to the two electrodes 6 and 6' mounted on the base 3, respectively. It is conceivable that more than two electrodes are arranged on the base 3 and the cover surface 4, respectively. Furthermore, it is conceivable that the number of electrodes on the base is different from the number of electrodes on the cover surface; for example, two electrodes can be arranged on the base and only one electrode can be arranged on the cover surface.

[0032] The contact portions 50 and 50' represent the corresponding surfaces of the ultrasonic actuator 1 and may be in direct contact with an element to be moved or adjusted relative to the ultrasonic actuator 1, such as an armature. However, since direct contact may lead to increased wear of the electromechanical material of the ultrasonic actuator 1, which generally has rather poor friction properties, it is preferred that friction elements are provided at the contact portions 50 and 50', with optimized friction and wear properties. In the presence of friction elements arranged at the contact portions 50 and 50', indirect contact is then achieved between the contact portions 50 and 50' of the ultrasonic actuator and the element to be moved or adjusted relative to the ultrasonic actuator 1.

[0033] Figure 3 is a perspective view of a potential embodiment of an electric machine 100, implemented as having Figure 1 2 and the linear drive of the ultrasonic actuator 1. Here, the ultrasonic actuator is inserted into a mounting device 110, which itself is mounted in a Figure 3The ultrasonic actuator is connected in an invisible manner to a higher-level fixing element (e.g. a base) so that a fixed mounting of the ultrasonic actuator is achieved.

[0034] The armature 120 is in the form of a spatial structure sheet, arranged to move in the opposite direction to the ultrasonic actuator or to be movable relative to the ultrasonic actuator, and has two elongated running surfaces 122, 122' formed integrally therewith and arranged parallel to each other, and the running surfaces 122, 122' are connected to the contact parts 50, 50' of the ultrasonic actuator via friction elements ( Figure 3 (not visible in Figure 2) indirectly contacts the ultrasonic actuator.

[0035] Due to its special design, the armature 120 has in particular specific elastic properties, with which the running surfaces 122, 122' are pressed or pressed with a defined force against the friction elements or contact portions 50, 50' after the mounting device 110 has been inserted into the armature 120. This force ensures, on the one hand, that the ultrasonic actuator is subjected to the preload required for a reliable and defined operation and, on the other hand - due to the geometry of the ultrasonic actuator according to the invention - that the ultrasonic actuator is subjected to a torque in the counterclockwise direction, thereby pressing it firmly against the mounting device 110 so that the ultrasonic actuator is firmly held therein.

[0036] The torque thus applied to the ultrasonic actuator causes a clockwise counter torque acting on the armature 120. Designed integrally with the armature 120 are two guides 125 and 125' and two support portions 126 and 126', the two guides 125 and 125' being spaced apart from each other and having different shapes, and the two support portions 126 to 126' being arranged opposite to each other and at Figure 3 It is also conceivable to provide the guides 125, 125' and / or the bearings 126, 126' as separate components, which are connected to the armature 120, for example by screws or an adhesive connection.

[0037] The guides 125, 125' are in sliding engagement with two round rod-shaped guide elements 130, 130' made of steel and arranged parallel to each other. It is also conceivable to use guide elements 130, 130' made of ceramic. The guide part 124 with its guides forms a sliding guide together with the guide elements 130, 130', which is used to compensate for the friction that has been generated by the shape of the running surfaces 122, 122' and their contact with the friction elements of the ultrasonic actuator, so that the linear movement of the armature 120 is more precise.

[0038] The counter torque acting on the armature 120 ensures that the guides 125 and 125' are Figure 3The upper guide element 130 in the middle is in limited contact. The guide parts 125 and 125' each have a hole through which the guide element 130 protrudes. The cross-section of the guide parts 125, 125' is not circular, but each has a V-shaped area, the two side wings of which are used to support the guide element 130. Although Figure 3 In the case of the left guide portion 125, the V-shaped portion points downward, but in Figure 3 In the case of the right guide 125' in FIG. 1 , the V-shaped portion points upwards. The counter-torque acting on the armature 120 now causes the V-shaped portion of the guide 125, 125' or their flanks to support the guide element 130 with a defined force, so that at the same time, a defined mutual alignment occurs between the guide element 130 and the guide 125, 125'.

[0039] The force with which the flanks or legs of the V-shaped portion of the guides 125, 125' press against the guide element 130 can be influenced by the forces acting on the ultrasonic actuator 1 via the running surfaces 122, 122' of the armature 120, which forces depend mainly on the elastic properties of the metal sheet of the armature 120 and the geometry of the ultrasonic actuator. The higher these forces and the resultant torque acting on the ultrasonic actuator, the greater the corresponding counter-torque acting on the armature. Now, the further the guides 125, 125' are spaced apart from each other, the smaller the contact force of the flanks or legs of the V-shaped region of the guides 125, 125' against the guide element 130 due to the increased rod length. Therefore, the adjustment of these contact forces can also be achieved by the spacing of the guides 125, 125'.

[0040] A sliding bearing or sliding guide formed in this way is easy to assemble, relatively simple to implement and therefore overall cost-effective. The contact force can be tailored so that in particular low friction resistance is generated, against which the ultrasonic actuator must work. At the same time, such a sliding guide can withstand high mechanical loads and exhibit high operating precision.

[0041] Figure 4 In a separate way therefore as a basis Figure 3 The details of the motor are shown only according to Figure 1 2 is inserted into the mounting device 110. The mounting device 110 made of polyetheretherketone (PEEK) has a total of six holding parts 111, 111', 112, 112', 113, 113', which contact the ultrasonic actuator at different parts 52, 52', 54, 54', 56, 56' of the side surface 5 of the ultrasonic actuator, thereby firmly clamping or holding the ultrasonic actuator. Other materials for the mounting device 110 are also conceivable, in particular polymer materials, such as polyoxymethylene (POM) or polyamide (PA).

[0042] The two holding portions contacting the ultrasonic actuator at the longer side surface portions 52', 54 of the ultrasonic actuator are designed to be mechanically less elastic, thus being rigid and forming corresponding rigid holding portions 111, 111', while the two other holding portions contacting the ultrasonic actuator at the same longer but different side surface portions 52, 54' are mechanically elastic, thus having elastic properties and forming corresponding elastic contact portions 112, 112'. The holding portions 113, 113' contact the ultrasonic actuator at the shorter side surface portions 56, 56' and also have low mechanical elasticity.

[0043] The force F acting on the two friction elements 20 from the running surfaces 122, 122' of the armature 120 is Figure 4 , as also with the torque M acting on the ultrasonic actuator 1 from it, it attempts to rotate the ultrasonic actuator counterclockwise. Due to this torque M, the side portions 52' and 54 are pressed more strongly against the rigid contact portions 111 and 111', whereby the rigid contact portions 111 and 111' are therefore more firmly supported. At the same time, the side surface portions 52 and 54' attempt to move away from the elastic contact portions 112, 112' due to the acting torque M, but their elastic properties ensure constant contact with these side surface portions 52 and 54', so that the pressing force of the elastic contact portions 112, 112' on the side surface portions 52 and 54' is independent of the acting torque M.

[0044] Figure 5 The side view shows the Figure 3 Here, the cross-sectional shapes of the guide portions 125, 125' and the support portion 126 and their engagement with the guide elements 130, 130' are particularly shown. Figure 5 The forward facing guide portion 125 in the embodiment has a downwardly facing V-shaped portion, and the guide element 130 rests on or is supported by two flanks or legs of the V-shaped portion. Figure 5The only partially visible rearward-facing guide portion 125' has an upward-facing V-shaped portion, and the guide element 130 also rests on the two flanks or legs of the V-shaped portion. The counter-torque acting on the armature (caused by the torque acting on the ultrasonic actuator via the armature) is therefore used to press the guide element 130 and simultaneously align the guide element 130 in the guide portions 125, 125'. Opposite the guide portions 125 and 125', there are corresponding bearing portions 126, 126', although only the forward-facing bearing portion 126 is visible. This has a right-angled, groove-shaped recess, in which the guide element 130' is mounted with a certain gap. The bearing portion 126' has a cross-sectional geometry that is identical to the cross-sectional geometry of the bearing portion 126. The bearing portions 126 to 126' are used to prevent the bearing portion 124 of the armature 120 fixedly connected thereto from rotating around the guide element 130.

[0045] Figure 6 is a perspective view of another potential embodiment of the motor 100, implemented as having Figure 1 and the linear drive of the ultrasonic actuator 1 of FIG. 2 . Figure 3 or Figure 4 The mounting device 110 of the same construction comprises an elongated guide portion 116, 116' formed integrally therewith, the guide portion 116, 116' supporting a guide portion 125, 125' in the form of a bent rod or an inclined rod, the guide portion 125, 125' being formed integrally with an armature 120 in the form of a spatial structural metal plate, Figure 6 Only the guide 125 can be seen. By replacing the guides 116, 116' formed integrally with the support device 110 Figure 3 and Figure 5 The function of the guide element 130 in the embodiment allows a more compact design of the motor with the ultrasonic actuator according to the invention, which has fewer components and is also easier and faster to assemble.

[0046] List of reference numerals:

[0047] 1: Ultrasonic actuator

[0048] 2: Board

[0049] 3: Base (of plate 2)

[0050] 4: Covering surface (of plate 2)

[0051] 5: Side surface (of plate 2)

[0052] 6, 6': Electrode

[0053] 7, 7': Electrode

[0054] 8, 8': Side (of base 3)

[0055] 9, 9': Connecting line

[0056] 10: Parallelogram (inscribed in base 3)

[0057] 11: The larger interior angle (of the inscribed parallelogram 10)

[0058] 12, 12': Trapezoidal (of base 3)

[0059] 13, 13': The base of (trapezoid 12, 12')

[0060] 14: Diagonal of (trapezoid 12, 12')

[0061] 15: distance between the sides 16, 16' of the trapezoids 12, 12' opposite to the bases 13, 13' and the base of the other trapezoid

[0062] 16, 16': Sides (opposite to the bases 13, 13' of trapezoids 12, 12')

[0063] 20: Friction element

[0064] 50: Contact portion (of side surface 5)

[0065] 52, 52': part (of the side surface 5)

[0066] 54, 54': part (of the side surface 5)

[0067] 56, 56': part (of the side surface 5)

[0068] 100: Motor

[0069] 110: (Motor 100) mounting equipment

[0070] 111, 111': Rigid holding portion (holding device 110)

[0071] 112, 112': elastic holding portion (holding device 110)

[0072] 113, 113': Holding portion (holding device 110)

[0073] 116, 116': Guide portion (holding device 110)

[0074] 120: Armature

[0075] 122, 122': running surface (of the armature 120)

[0076] 125, 125': guide portion (of the armature 120)

[0077] 126, 126': Supporting portion (of the armature 120)

[0078] 130, 130': Guide element

Claims

1. An ultrasonic actuator (1) in the form of a plate (2) having a base (3), a cover surface (4) geometrically similar to the base, and side surfaces (5) interconnecting the base and the cover surface, wherein: The plate comprises an electromechanical material, and electrodes (6, 6', 7, 7') are arranged on a base of the plate and on a covering surface of the plate opposite to the base for exciting periodic deformation of the plate, and the base (3) comprises two side edges (8, 8'), the two side edges are arranged parallel to each other and form a contact portion (50, 50') of the side surface (5), and the two side edges of the base arranged parallel to each other together with a connecting line (9, 9') form a parallelogram (10) inscribed in the base, the connecting line interconnecting the corresponding end points of the side edges (8, 8') arranged parallel to each other, characterized in that in the inscribed parallelogram (10), an angle different from 90° is defined between adjacent edges, wherein The base (3) is octagonal, and a trapezoid (12, 12') adjoins each longer side of the inscribed parallelogram (10), and the base (13, 13') of each trapezoid (12, 12') coincides with the corresponding longer side of the inscribed parallelogram (10), Each trapezoid (12, 12') is an isosceles trapezoid, and The length of each diagonal (14) of the trapezoid (12, 12') is substantially equal to the distance (15) between the side (16, 16') of the trapezoid (12, 12') opposite to the base (13, 13') and the base (13, 13') of the corresponding other trapezoid (12, 12').

2. The ultrasonic actuator (1) according to claim 1, characterized in that: The greater internal angle (11) of the inscribed parallelogram has a value between 93° and 105°.

3. A motor (100) comprising an ultrasonic actuator (1) according to any one of the preceding claims, the motor (100) comprising a mounting device (110) for fixedly holding the ultrasonic actuator (1) and an armature (120) capable of moving relative to the ultrasonic actuator (1) and in frictional contact with the ultrasonic actuator (1).

4. The electric machine (100) according to claim 3, characterized in that: The mounting device (110) comprises four retaining parts (111, 111', 112, 112', 113, 113') in contact with the ultrasonic actuator (1) at the longer part (52, 52', 54, 54') of the side surface (5), two of which are mechanically rigid and form rigid retaining parts (111, 111'), and two retaining parts have elastic properties and form elastic retaining parts (112, 112').

5. The electric machine (100) according to claim 4, characterized in that: The mounting device (110) comprises two further retaining portions (113, 113'), each of which contacts a portion (56, 56') of the side surface (5) of the ultrasonic actuator (1) between areas of the side surface (5) contacted by a respective rigid retaining portion (111, 111') and a respective elastic retaining portion (112, 112').

6. The electric machine (100) according to claim 3, characterized in that: The armature (120) is in the form of a spatial structure sheet and comprises two elongated and mutually parallel running surfaces (122, 122'), the running surfaces directly or indirectly contacting the ultrasonic actuator (1) at the contact portion (50, 50') of the ultrasonic actuator (1), clamping the ultrasonic actuator (1) between the running surfaces in such a way that a torque acts on the ultrasonic actuator (1), and the portion (52, 52', 54, 54') of the side surface (5) in contact with the rigid contact portion is pressed against the rigid contact portion by means of the running surfaces.

7. The electric machine (100) according to claim 3, characterized in that: The armature (120) comprises at least two guide parts (125, 125') spaced apart from each other, and two round rod-shaped guide elements (130, 130') arranged parallel to each other pass through holes of the guide parts (125, 125') so as to enable sliding relative movement between the guide parts (125, 125') and the guide elements (130, 130').

8. The electric machine (100) according to claim 3, characterized in that The armature (120) includes at least two guide portions (125, 125') spaced apart from each other, the guide portions (125, 125') contacting guide portions (116, 116') of the mounting device (110) formed integrally therewith, so as to enable sliding relative movement between the guide portions (125, 125') and the guide portions (116, 116') of the mounting device (110).

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