WO2023241759A1 - Moteur à ultrasons - Google Patents

Moteur à ultrasons Download PDF

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Publication number
WO2023241759A1
WO2023241759A1 PCT/DE2023/100444 DE2023100444W WO2023241759A1 WO 2023241759 A1 WO2023241759 A1 WO 2023241759A1 DE 2023100444 W DE2023100444 W DE 2023100444W WO 2023241759 A1 WO2023241759 A1 WO 2023241759A1
Authority
WO
WIPO (PCT)
Prior art keywords
ultrasonic motor
motor according
ultrasonic
driven
polygonal plate
Prior art date
Application number
PCT/DE2023/100444
Other languages
German (de)
English (en)
Inventor
Alexej Wischnewski
Original Assignee
Physik Instrumente (Pi) Gmbh & Co. Kg
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Physik Instrumente (Pi) Gmbh & Co. Kg filed Critical Physik Instrumente (Pi) Gmbh & Co. Kg
Publication of WO2023241759A1 publication Critical patent/WO2023241759A1/fr

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Classifications

    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02N—ELECTRIC MACHINES NOT OTHERWISE PROVIDED FOR
    • H02N2/00—Electric machines in general using piezoelectric effect, electrostriction or magnetostriction
    • H02N2/0095—Electric machines in general using piezoelectric effect, electrostriction or magnetostriction producing combined linear and rotary motion, e.g. multi-direction positioners
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02N—ELECTRIC MACHINES NOT OTHERWISE PROVIDED FOR
    • H02N2/00—Electric machines in general using piezoelectric effect, electrostriction or magnetostriction
    • H02N2/10—Electric machines in general using piezoelectric effect, electrostriction or magnetostriction producing rotary motion, e.g. rotary motors
    • H02N2/12—Constructional details
    • H02N2/123—Mechanical transmission means, e.g. for gearing
    • H02N2/126—Mechanical transmission means, e.g. for gearing for conversion into linear motion
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02N—ELECTRIC MACHINES NOT OTHERWISE PROVIDED FOR
    • H02N2/00—Electric machines in general using piezoelectric effect, electrostriction or magnetostriction
    • H02N2/10—Electric machines in general using piezoelectric effect, electrostriction or magnetostriction producing rotary motion, e.g. rotary motors
    • H02N2/16—Electric machines in general using piezoelectric effect, electrostriction or magnetostriction producing rotary motion, e.g. rotary motors using travelling waves, i.e. Rayleigh surface waves
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02N—ELECTRIC MACHINES NOT OTHERWISE PROVIDED FOR
    • H02N2/00—Electric machines in general using piezoelectric effect, electrostriction or magnetostriction
    • H02N2/10—Electric machines in general using piezoelectric effect, electrostriction or magnetostriction producing rotary motion, e.g. rotary motors
    • H02N2/16—Electric machines in general using piezoelectric effect, electrostriction or magnetostriction producing rotary motion, e.g. rotary motors using travelling waves, i.e. Rayleigh surface waves
    • H02N2/163—Motors with ring stator

Definitions

  • the invention relates to an ultrasonic motor.
  • Piezoelectric friction contact drives are known from the prior art, in which the friction contact is designed in the form of a threaded engagement. They can be used, for example, as spindle drives in various types of mechanisms, such as in linear drives, in precise closure and metering systems, in valves, in precise cutting drives, in control drives, in precise positioning devices, such as in technological coordinate tables, in multi-coordinate positioning devices, in tripods or hexapods , in optical laser systems and similar devices, and in precision medical devices, e.g. pumps, syringes, insulin pumps or devices for bone lengthening.
  • spindle drives in various types of mechanisms, such as in linear drives, in precise closure and metering systems, in valves, in precise cutting drives, in control drives, in precise positioning devices, such as in technological coordinate tables, in multi-coordinate positioning devices, in tripods or hexapods , in optical laser systems and similar devices, and in precision medical devices, e.g. pumps, syringes, insulin pumps or devices for
  • Lasers are used in many areas of technology, be it in metrology, medical technology, metal processing, etc.
  • the laser beam is usually precisely directed or guided with the help of tilting mirrors.
  • the required precision of laser beam steering is achieved with the help of micrometer screws. These are often operated manually.
  • manual adjustment of the tilting mirrors is not possible or undesirable, for example within a vacuum chamber, in a lithography machine or a tachymeter.
  • Piezoelectric friction contact drives are often used for automatic positioning of the tilting mirrors.
  • an element to be driven i.e. the rotor or rotor
  • the actuator is connected or coupled to the actuator by a frictional contact, with a targeted deformation or movement of the actuator caused by electrical control being transmitted to the element to be driven by means of the frictional contact.
  • the applicant's DE 102009 049 719 A1 describes a plate-shaped actuator which is on its top side as well as on its The bottom has two electrodes spaced apart by a separation area, the electrodes on the top being arranged offset from the electrodes on the bottom.
  • an ultrasonic motor which has a rectangular piezoelectric ultrasonic actuator on which two friction elements are arranged at a distance from one another, and the ultrasonic actuator is divided in the form of a plate into two pairs of diagonally opposite sections, wherein a part of an acoustic standing wave generator is arranged in each of the diagonal sections, and a total of two generators are present, each consisting of two parts that can be operated in antiphase.
  • US 2005/0275318 A1 discloses a stacked piezoelectric transducer in which the electrodes arranged on the respective surfaces of the individual layers have a design that differs from one another, which takes into account the different expansion behavior of the transducer along the stacking direction.
  • WO 2022/176560 A1 teaches a rotary ultrasonic motor in which a shaft to be driven is operatively connected to a rotor via a spring element, the rotor being driven via a vibrator in which traveling waves are generated.
  • the piezo actuator cannot drive the screw faster than a few 10 kHz, because when a certain frequency is exceeded, the static friction between the actuator and the screw changes into sliding friction, which results in a relative movement or sliding comes between the actuator and the screw without the screw being driven and simply standing still.
  • US 4,734,610 A discloses a vibrating shaft motor having a circular vibrating member which has a thread and which is coupled to a unit which generates a traveling wave in the vibrating member, this traveling wave propagating along a circumferential direction of the vibrating member.
  • a movable part is in effective contact with the vibration part and engages with its correspondingly designed thread in the thread of the vibration part.
  • DE 4438 876 B4 describes a piezoelectric motor with a stator on which a piezoelectric oscillator is arranged, and with a rotor, the rotor being in effective contact with the piezoelectric oscillator.
  • the piezoelectric oscillator has three ultrasonic wave generators.
  • a piezoelectric ultrasonic motor with a threaded contact or with a threaded engagement between a driving element and an element to be driven is known from US Pat. No. 4,734,610 A.
  • the driving element is designed as a thin-walled nut made of metal and the element to be driven is designed as a threaded rod, the nut and the threaded rod being in frictional engagement.
  • Thin piezoelectric discs are glued to the end faces of the nut.
  • the mother takes on the task of the acoustic resonator, and the piezoelectric disks form the surfaces for the exciters of the acoustic traveling wave in the thin-walled mother.
  • the publication US 6 940 209 B2 discloses a piezoelectric ultrasonic motor with a threaded contact or with a threaded engagement between a driving element and an element to be driven.
  • the driving element is a metal tube on which piezoelectric exciter plates are arranged.
  • the element to be driven is designed as a threaded rod and is in frictional engagement with the threaded insert.
  • the metal tube represents an acoustic resonator, and the piezoelectric excitation plates arranged on it generate an elastic traveling wave in the tube, which is aligned longitudinally to the axial axis of the tube. The traveling wave is transmitted to the threaded insert, and the threaded or frictional contact between the threaded insert and the threaded rod results in a rotation of the threaded rod and thus ultimately a linear movement of the threaded rod.
  • the ultrasonic motor comprises at least one one-piece annular piezoelectric ultrasonic actuator with at least one generator for generating a plane acoustic traveling wave, a substantially annular contact element with an outer and inner circumferential surface and an element to be driven.
  • the contact element is completely surrounded by the actuator on its outer peripheral surface.
  • the contact element is provided with a thread on its inner peripheral surface and is in threaded engagement with the element to be driven which is provided with an external thread.
  • the flat acoustic traveling wave created by electrical excitation in the actuator is transmitted to the contact element, so that the element to be driven rotates.
  • a disadvantage of the drive according to DE 10 2010 022 812 B4 is the fact that in order to counteract the torque developed by the motor during operation, the actuator is clamped on its outer peripheral surface with the aid of a holding element or is glued into it. This causes the actuator to be strongly damped, which means that the oscillation amplitude of the contact element becomes smaller and the torque and speed decrease. Therefore, the ultrasonic motor known from DE 10 2010 022 812 B4 requires a relatively high electrical voltage to operate, as a result of which the actuator becomes warm and the efficiency of the motor decreases.
  • Another disadvantage of the ultrasonic motor according to DE102010 022 812 B4 is a low reliability of the adhesive connection of the contact element to the piezoelectric actuator when the diameter of the contact element is large.
  • the contact element is glued into the piezoelectric actuator.
  • the size of the outer circumferential surface becomes critical for an adhesive connection.
  • the object of the invention is therefore to provide an ultrasonic motor which overcomes the disadvantages of the ultrasonic motors known from the prior art and which in particular has a high level of efficiency and can therefore be operated with a comparatively low electrical voltage, so that it can be operated during is heated only slightly or not at all during operation, which ensures high operational reliability. Furthermore, it is an object of the invention to provide an ultrasonic motor that can be operated with a simply constructed and therefore more cost-effective electrical excitation device.
  • the ultrasonic motor according to the invention has at least one piezoelectric ultrasonic actuator, which comprises or contains at least one generator for generating a planar acoustic traveling wave. Furthermore, the ultrasonic motor according to the invention has a drive element and an element to be driven by the drive element, the drive element having a threaded inner peripheral surface and thus an internal thread, as well as a Has outer circumferential surface, and wherein the drive element is inserted into the ultrasonic actuator and preferably glued into it such that an inner circumferential surface of the ultrasonic actuator surrounds or surrounds the drive element on its outer circumferential surface.
  • the element to be driven has an external thread which engages with the internal thread of the drive element and through the thread engagement the planar acoustic traveling wave generated by the generator of the ultrasonic actuator can be transferred from the ultrasonic actuator to the drive element, whereby a rotation of the element to be driven can be caused .
  • the actuator of the ultrasonic motor according to the invention is designed as a polygonal plate or polygonal disk, i.e. as a plate or disk whose thickness is significantly smaller than its remaining dimensions, the plate or disk having a polygonal shape.
  • the polygonal plate or disk has two large main surfaces and at least three smaller side surfaces or peripheral surfaces connecting the two main surfaces. Due to the polygonal shape of the actuator and the resulting eigenmodes for standing waves, it is particularly possible to fasten the actuator or the polygonal plate in a holder with low losses and without strong damping.
  • the ultrasonic actuator or the polygonal plate has at least one active generator for generating a planar acoustic standing wave.
  • the specific standing waves that can be generated in this way have the advantage that the maximum of their vibration amplitudes in the radial and circumferential directions is present essentially on the thread surface or in the area of the thread surface of the drive element inserted into the actuator and coupled to it, so that the drive energy of the drive element is extremely efficient can be transferred to the element to be driven which is in threaded engagement with it.
  • the contour of the polygonal plate has the shape of a triangle with three side or circumferential surfaces or a square or a rectangle each with four side or circumferential surfaces or a pentagon with five side or circumferential surfaces or a hexagon with six side or peripheral surfaces or an octagon with eight side or peripheral surfaces.
  • the actuator can be held on the corresponding side surfaces with low losses.
  • a contour of the polygonal plate with more than eight side or peripheral surfaces is also conceivable.
  • the ultrasonic actuator or the polygonal plate has only one active generator of acoustic standing waves. This enables the use of a simple single-phase electrical excitation device for electrical excitation of the ultrasonic actuator.
  • the ultrasonic actuator or the polygonal plate can also have two active generators, through whose simultaneous excitation a planar acoustic standing wave can be generated in it.
  • the trajectory of a friction contact point of the drive element can be changed and the movement properties of the part to be driven can thus be influenced.
  • planar acoustic traveling wave can also be advantageous for the planar acoustic traveling wave to be generated by superimposing two or more than two planar ones Standing waves of the same frequency can be produced. This results in a particularly effective and reliable drive of the element to be driven.
  • longitudinal standing waves can be generated in the polygonal plate along its circumference or along one of its diagonals or along a direction that runs perpendicular to the side or circumferential surfaces.
  • a bend in the plane about the axial axis can be stimulated in the polygonal plate.
  • further planar standing waves can be excited in the polygonal plate. Such standing waves have a particularly high coupling factor.
  • the drive element is a disk with a round, triangular, square, square, pentagonal, hexagonal, octagonal or an n-sided polygonal contour.
  • the drive element can have recesses in the form of openings or slots, whereby the openings can be round or elongated openings.
  • the drive element can be formed from individual segments. This makes it possible to reduce the mechanical stresses on the contact surface between the drive element and the ultrasonic actuator or the polygonal plate when the ultrasonic actuator heats up or when there are large vibration amplitudes on the ultrasonic actuator, which increases the operational reliability of the motor.
  • the recesses are filled with a sound-absorbing material, whereby parasitic vibrations of the ultrasonic actuator or the polygonal plate are effectively dampened, resulting in a more effective drive via the Frictional contact between the drive element and the element to be driven is achieved.
  • an elastic contour element preferably made of a metallic or a ceramic material, is arranged on the side or peripheral surfaces of the polygonal plate.
  • the use of such an elastic element, which compresses the ultrasonic actuator, increases the strength of the ultrasonic actuator. This makes it possible to apply higher power to the actuator, which results in a higher movement speed of the element to be driven.
  • the element to be driven is designed as a solid or as a hollow threaded rod with at least one longitudinal opening or at least one slot, which preferably runs in the axial direction. This reduces the start and stop times of the ultrasonic motor, as well as its amplitudes of parasitic oscillations.
  • the element to be driven is designed as a hollow threaded rod, it can be advantageous if the corresponding cavity in the element to be driven is filled with a sound-absorbing material. This makes it possible to reduce the parasitic vibrations that arise in the element to be driven, thereby improving the engine function.
  • the ultrasonic motor can have a pressing device with which the element to be driven is pressed against the drive element and which acts on the element to be driven in a direction that runs longitudinally to the vertical axis of the ultrasonic actuator. This ensures reliable operation of the ultrasonic motor.
  • the pressing device is designed as part of the element to be driven or is arranged in it. This leads to a simplified construction and enables particularly compact dimensions of the ultrasonic motor.
  • the ultrasonic actuator is held on its outer peripheral surfaces. This makes it possible to achieve a particularly simple and loss-free holder.
  • the ultrasonic motor can have a fastening device for the ultrasonic actuator or the polygonal plate, the fastening device comprising acoustic resonance elements with the aid of which the ultrasonic actuator can be connected to a base plate or to a motor housing.
  • the acoustic resonance elements can reduce the mechanical losses at the fastening points.
  • each of the generators of planar standing waves may prove advantageous for each of the generators of planar standing waves to have a three-layer structure consisting of an excitation electrode, a common electrode and a piezoelectric material arranged between the two electrodes between them, or a multilayer or multilayer structure in which the electrode layers and the layers of the piezoelectric material are arranged alternately.
  • the multilayer or multilayer structure allows the electrical excitation voltage to be reduced.
  • Fig. 6 Ultrasonic actuator of an ultrasonic motor according to the invention with a hexagonal shape or contour and a drive element with a circular contour inserted therein
  • Fig. 8 Ultrasonic actuator of an ultrasonic motor according to the invention with a hexagonal contour and a drive element inserted therein with a hexagonal contour and elastic contour elements
  • Figs. 10, 11 Sectional views to illustrate possible engagement geometries between the element to be driven and the drive element of an ultrasonic motor according to the invention
  • Figs. 14, 15 Ultrasonic motors according to the invention with different embodiments for holding the ultrasonic actuator
  • Fig. 20 Embodiment of a generator for generating standing waves in the ultrasonic actuator of an ultrasonic motor according to the invention with a single piezoelectric layer
  • Fig. 21 Embodiment of a generator for generating standing waves in the ultrasonic actuator of an ultrasonic motor according to the invention with a multi-layer structure
  • Fig. 24 Illustrations explaining the functional principle of the ultrasonic motor according to the invention according to the Figs. 3 and Fig.4, where representation a) corresponds to a top view, and representation b) corresponds to a side view
  • FIG. 25 Electrical circuit of the ultrasonic motor according to the invention according to FIG. 1 for a single-phase excitation
  • Fig. 26 Electrical circuit of the ultrasonic motor according to the invention according to FIG. 1 or FIG. 27: Electrical circuit of the ultrasonic motor according to the invention according to FIG. 4 for three-phase excitation
  • the ultrasonic motor according to the invention has an ultrasonic actuator 1 and an element 2 to be driven.
  • the ultrasonic actuator 1 in the form of a rectangular disk or plate is made of a piezoelectric ceramic and corresponds to a polygonal plate or disk 4.
  • the polygonal plate 4 has an eccentrically arranged opening or opening 5, on the inner peripheral surface of the opening or the Breakthrough 5 has a thin-walled drive element 6 compared to the diagonal dimensions of the ultrasonic actuator 1.
  • the drive element 6 and the opening 5 have a round shape, although an n-polygonal shape is also conceivable.
  • the polygonal plate 4 is separated by two mutually perpendicular cutting planes P1, P2, which pass through the middle of the opposite outer peripheral or side surfaces 18.
  • the opening 5 is arranged asymmetrically with respect to the cutting plane P1 and symmetrically with respect to the cutting plane P2. It is conceivable that the polygonal plate 4 could also be made of another piezoelectric material, e.g. B. a single crystal material.
  • the inner peripheral surface 7 of the drive element 6 has a thread, not shown, with a thread height q.
  • the element 2 to be driven is designed as a solid or solid threaded rod or threaded rod 9 with a thread 11 on its outer peripheral surface 10, the thread 11 also having a thread height q.
  • the element 2 to be driven is screwed into the drive element 6.
  • the thread on the inner peripheral surface 7 of the drive element 6 and the thread 11 on the outer peripheral surface 10 of the element 2 to be driven form a friction contact.
  • the polygonal plate or disk 4 of the ultrasonic actuator 1 shown in FIG. 1 has an active generator 13 for a planar standing wave.
  • An active generator for a planar standing wave is to be understood as meaning a generator which is actually electrically excited during operation of the actuator by means of an electrical excitation device 3 and only this active generator generates a planar acoustic standing wave.
  • a planar standing wave is to be understood as meaning a wave that propagates in the plane of the polygonal plate, the oscillation amplitude of the material particles of the polygonal plate being at least one order of magnitude smaller in the axial direction than in the directions of the plate plane.
  • the point 22 indicates a small area on the inner peripheral surface of the polygonal plate 4, which, when the active generator 13 is excited, passes through an elliptical trajectory 23 shown in FIG.
  • Each of the two generators 13 is connected with its connections 15 and 16 via a changeover switch 25 to the electrical excitation device 3, which consists of an electrical generator 17 for an electrical alternating voltage U1.
  • the alternating electrical voltage generator 17 is intended to electrically excite the active generator 13.
  • Changing the direction of movement 26 or 27 of the element 2 to be driven takes place by switching the electrical excitation device 3 between the two active generators 13 using the switch 25.
  • the single-phase control of the ultrasonic actuator 1 enables a simple electronic switching of the electrical excitation device 3.
  • FIG. 2 illustrates in representations a) and b) instantaneous deformations of the polygonal plate at /2 and 3JI/2 of its oscillation period when an active generator 13 is excited, calculated using FEM.
  • the point 22 located on the inner peripheral surface 7 passes through an elliptical Trajectory 23.
  • the polygonal plate 4 of the ultrasonic motor shown in Fig. 1 is illustrated for the realization of a reversible movement of the element 2 to be driven.
  • the first generator 13 (see Fig. 2c)) is connected to the excitation device 3 for a first direction of movement.
  • the elliptical trajectory of the point 22 runs tangentially to the opening 5 and at an angle a to the cutting plane P2.
  • the second generator 13 is connected to the excitation device 3, so that the elliptical trajectory changes its inclination mirror-symmetrically with respect to the section plane P2 (Fig. 2d)).
  • FIG. 2e illustrates the polygonal plate 4 of the ultrasonic motor shown in FIG. 1, with the first generator 13 and the second generator 13 being active at the same time.
  • both generators are supplied with two electrical voltages at the same time.
  • the possible trajectories of point 22 are indicated by dashed ellipses.
  • the ultrasonic actuator 1 of an ultrasonic motor according to the invention is designed here as a square (Fig. 3) or hexagonal (Fig. 4) polygonal plate 4 made of a piezoelectric ceramic, which has an opening or a breakthrough 5 , with a thin-walled drive element 6 sitting on the inner peripheral surface of the polygonal plate 4 compared to the diagonal dimensions of the ultrasonic actuator 1.
  • the polygonal plate 4 could also be made of another piezoelectric material, e.g. B. a single-crystalline material.
  • the drive element here has a round shape, although an n-polygonal shape is also possible.
  • the polygonal plate 4 of the ultrasonic motor comprises at least one generator 12 for a planar traveling wave, which is formed from two or more than two active generators 13 for planar standing waves.
  • the ultrasonic motor shown in Fig. 3 contains two active generators 13. They are spatially arranged offset from one another by 90°.
  • the generators 13 are part of the polygonal plate 4 or are designed integrally with it, so that no acoustic boundary is formed between them, ie the acoustic waves pass freely and without reflection at the geometric boundary from one generator 13 into an adjacent generator 13.
  • Each of the generators 13 is connected with its connections 15 and 16 to the electrical excitation device 3, which consists of two or more than two electrical generators 17 for alternating electrical voltages U1...Un.
  • the generators 17 are intended for electrically exciting the generators 13 of the planar standing waves. For reasons of clarity, only two generators 17 for the electrical alternating voltages U1 and U2 are shown in FIG. The generators are rotated relative to each other about the vertical axis 14 of the ultrasonic actuator 1 in such a way that the planar standing waves generated by them are shifted by A/4, ie by 90°, relative to one another.
  • the two generators 17 of the electrical excitation device 3 each provide an electrical alternating voltage, the frequency of which essentially corresponds to the resonance frequency of the plane acoustic standing waves generated, the phase of each voltage being shifted by plus 90° or minus 90° relative to one another, and the amplitudes of the electrical voltages are equal.
  • the two-phase control of the generator 12 or the generators 13 enables a relatively simple electronic circuit of the electrical excitation device 3.
  • the ultrasonic motor shown in FIG. 4 differs from the ultrasonic motor shown in FIG.
  • the generators are rotated relative to each other about the vertical axis 14 of the ultrasonic actuator 1 in such a way that the plane standing waves generated by them are shifted by A/3, ie by 120°, relative to each other.
  • the three generators 17 of the electrical excitation device 3 each provide an electrical alternating voltage, the frequency of which essentially corresponds to the resonance frequency of the plane acoustic standing waves generated, the phase of each voltage being shifted by 120 ° relative to one another and the amplitude of the electrical voltages are equal.
  • the contour of the polygonal plate 4 of the ultrasonic motors according to the invention shown in FIGS. 2 and 3 can also be a triangle, a pentagon or an n-polygon.
  • the polygonal plate 4 shows different embodiments of the polygonal plate 4 of an ultrasonic motor according to the invention in illustrations 28 to 33.
  • the polygonal plate has two large main surfaces 19 and at least three outer peripheral or side surface surfaces 18.
  • the polygonal plate can be triangular (see illustration 28), square (see illustration 29), rectangular (see illustration 30), pentagonal (see illustration 31), hexagonal (see illustration 32) or octagonal (see illustration 33). or have a different type of n-sided polygonal contour.
  • the pointed corners of the polygonal plate shown in FIG. 5 can be separated or rounded.
  • the drive element 6 shows the ultrasonic actuator 1 in the form of a hexagonal or hexagonal polygonal plate 4 of the ultrasonic motor according to FIG. 4.
  • the drive element 6 with a round contour is inserted into this.
  • P denotes the diameter of the circle C connecting all vertices of the polygonal plate
  • S denotes the circumference of the circle C.
  • the thickness of the ultrasonic actuator 1 or the polygonal plate 4 between the main surfaces 19 is h.
  • H denotes the radial distance between the inner circumferential surface 7 of the drive element 6 and the circle C.
  • D denotes the diameter based on the inner circumferential surface 7 of the drive element 6
  • L denotes the circumference based on the inner circumferential surface 7 of the drive element 6.
  • the sizes D and L refer each to the corresponding dimension that is present at half the thread height q (see Fig. 10 and Fig. 11).
  • the thickness h of the ultrasonic actuator 1 is chosen so that it is less than H/3.
  • the wall thickness t of the drive element 6 is smaller than H/8. It is particularly advantageous if S is a multiple of H.
  • the thin-walled drive element 6 is made of a hard, abrasion-resistant material whose hardness and abrasion resistance exceeds the hardness and abrasion resistance of the piezoelectric material of the ultrasonic actuator. Examples of such materials are heat-treated steel, oxide ceramics based on alumina, zirconium oxide, sialon, silicon nitride, metal ceramics based on tungsten carbide and titanium carbide.
  • the thin-walled drive element 6 is directly bonded to the ultrasonic actuator using an organic adhesive (e.g. epoxy resin).
  • the adhesive can contain solid non-organic components such as: B. contain oxide ceramic particles, metal particles or metal ceramic particles.
  • the drive element 6 can be indirectly connected to the ultrasonic actuator via an intermediate element (not shown in FIG. 6).
  • This intermediate element preferably has a thickness k, where k is less than 0.1 H. It is advantageous if the intermediate element consists of a material whose modulus of elasticity and coefficient of thermal expansion correspond approximately to the modulus of elasticity and the coefficient of thermal expansion of the piezoelectric material of the ultrasonic actuator. An example of such a material is a special oxide or metal ceramic.
  • the intermediate element can be made by a cohesive material Connection, realized via a slightly melting glass, can be connected to the polygonal plate 4 of the ultrasonic actuator 1.
  • the drive element 6 is designed as a ring or hollow cylinder with circular outer and inner circumferential surfaces according to illustration 34, while according to illustration 35 it has an outer contour with eight of each other distinguishable surfaces 41 has a hexagonal contour or shape.
  • the drive element has round openings or recesses or openings 42 (representation 36) or elongated openings or openings 43, 44 (representations 37 and 38).
  • the drive element 6 can also have slots 45 which are not continuous as shown in illustration 39 of FIG. 7. According to illustration 40 of FIG. 7, the slots can also be continuous, so that the drive element 6 consists of individual ring or hollow cylinder segments. It is conceivable that the openings or openings 42, 43, 44 or the slots 45 are filled with a sound-absorbing material.
  • FIG. 8 shows an ultrasonic actuator of an ultrasonic motor according to the invention in the form of a polygonal plate 4 having six outer circumferential or side surfaces 18 according to illustration 32 of FIG. 5 or according to FIG. 6, in which a drive element 6 with an eight Having outer peripheral surfaces, ie a hexagonal shape as shown in illustration 35 of FIG. 7 is used.
  • the polygonal plate 4 On its outer circumferential or side surfaces 18, the polygonal plate 4 is provided with an elastic contour element 47, which tensions or biases the polygonal plate 4 in the radial direction.
  • the elastic contour element 47 has a thickness d that is less than 0.1 H (see Fig. 6) and is made of steel.
  • the elastic contour element 47 can also be made of oxide ceramic, aluminum oxide or another hard ceramic.
  • FIG. 9 shows different embodiments for an element 2 to be driven of an ultrasonic motor according to the invention in illustrations 48 to 55.
  • the element to be driven is designed as a fully threaded rod made of a hard and abrasion-resistant material (e.g. heat-treated steel, oxide or metal ceramic).
  • a hard and abrasion-resistant material e.g. heat-treated steel, oxide or metal ceramic.
  • FIGS. 49-52 and 55 of FIG. 9 it is possible to design the element to be driven as a hollow threaded rod, with the corresponding inner opening or cavity 57 having a round shape.
  • other geometries of the inner opening are also conceivable (e.g. a polygonal shape).
  • a rod 58 made of a sound-absorbing material can be inserted into the cavity 57 of the hollow threaded rod 2 as shown in illustration 50 of FIG. 9.
  • This rod 58 is made of an elastic material such as. B. Rubber.
  • the elastic material can be filled with hard particles such as B. be filled with metal particles.
  • the rod 58 is made of a viscoelastic material, e.g. B. a thermoplastic material, the viscoelastic material containing particles, e.g. B. can be filled with metal and / or rubber particles.
  • the rod 58 can also be made of a hard porous material, such as. B. made of porous oxide ceramic, the pores of which have a filled with viscous material.
  • the rod 58 can, for example, also be made of a hard material such as steel, oxide ceramic, metal ceramic, with a layer of sound-absorbing material (e.g. rubber, epoxy resin or similar) being arranged between the rod 58 and the element 2 to be driven.
  • a layer of sound-absorbing material e.g. rubber, epoxy resin or similar
  • the rod 58 like the element 2 to be driven, is designed as a hollow rod, and the rod 58 has an axially arranged opening 60 in which a further sound-absorbing rod 61 is located, between the rod 58 and the sound-absorbing rod 61 a layer 59 of a sound-absorbing material is arranged.
  • the element to be driven which is designed as a hollow threaded rod, can have 2 longitudinal openings 62 or longitudinal slots 63.
  • the element 2 to be driven which is designed as a fully threaded rod, can have one or more longitudinal slots 63.
  • the thread 10 shows a possible thread engagement between a drive element 6 and an element 2 to be driven of an ultrasonic motor according to the invention.
  • the thread 8 provided on the drive element 6 and the thread 11 provided on the element 2 to be driven have an isosceles triangular shape.
  • the thread pitch can be 0.1mm to a few mm per thread, while the thread height is q.
  • threads 8, 11 show a further possible thread engagement between a drive element 6 and an element 2 to be driven of an ultrasonic motor according to the invention.
  • Both threads 8, 11 have a non-isosceles triangular shape.
  • the surface of threads 8 and 11 be provided with a solid, abrasion-resistant material layer.
  • layers made of CrN, CrCN, (Cr, W)N, (Cr, AI)N, NbN-CrN, TiN, TiCN, (Ti, AI)N or V2O5 are suitable for this.
  • the element 2 to be driven of an ultrasonic motor according to the invention is pressed against the drive element 6 with the aid of a pressing device 64, having a leaf spring 65.
  • the element 2 to be driven can also be pressed against the drive element 6 with the aid of a helical spring, which acts on the element 2 to be driven along the vertical axis 14 of the ultrasonic actuator or the polygonal plate 1.
  • the ultrasonic actuator 1 or the polygonal plate 4 is supported and held by an elastic ring 66 located on a motor housing 67.
  • the elastic ring 66 supports the ultrasonic actuator 1 at the points of minimum vibration speeds of the large main surfaces 19, whereby the mechanical losses in the elastic ring 66 are reduced.
  • the elastic ring 66 is made of rubber, but can also be made of polyurethane or Teflon.
  • the ultrasonic motor according to the invention shown there has an ultrasonic actuator 1 or a polygonal plate 4 with a hexagonal contour, which is held on its outer peripheral or side surfaces 18 via a holder 72.
  • the holder 72 has a thin hexagonal holding element 73 into which the ultrasonic actuator 1 is pressed or glued.
  • the holder 72 has projections or acoustic resonance elements 74, with the help of which the holding element 73 is connected to a base plate 75.
  • the drive element 6 has projections or acoustic resonance elements 74.
  • the projections or resonance elements 74 of the drive element 6 are connected to the base plate 75. Fastening the ultrasonic actuator 1 via the drive element 6 with the help of the projections 74 also increases the rigidity of the ultrasonic motor significantly.
  • FIG. 17 shows an exploded view of an ultrasonic motor according to the invention, in which a square-shaped ultrasonic actuator 1 is combined with a drive element 6 as shown in illustration 78 of FIG. 16, the drive element 6 having projections or resonance elements 74, which in turn are connected to the base plate 75 are connected.
  • the ultrasonic motor according to the invention shown there has several ultrasonic actuators 1 or polygonal plates 4 on.
  • the four ultrasonic actuators 1 or polygonal plates 4 are connected to one another via the resonance elements 74, each of the resonance elements 74 in turn being connected to the drive element 6. It is conceivable, instead of the four ultrasonic actuators 1 shown here, to use only two or three, or even more than four ultrasonic actuators 1 or polygonal plates 4 for the ultrasonic motor according to the invention.
  • FIG. 19 shows a schematic top view of an ultrasonic actuator 1 or a polygonal plate 4 of an ultrasonic motor according to the invention with an n-polygonal contour for the arrangement of the generators 12 for the planar traveling wave and the active standing wave generators 13 for a planar standing wave.
  • the generators 12 - relative to the vertical axis 14 - are relative to each other by the wavelength A, i.e. H. shifted by the angle 2TT.
  • the standing wave generators 13 To generate a traveling wave in each of the generators 12 with the aid of two standing waves, the standing wave generators 13 must be shifted relative to one another - based on the vertical axis 14 of the ultrasonic actuator 1 - by the angle A/4 or TT/2.
  • the standing wave generators 13 in each of the generators 12 must be shifted relative to one another - based on the vertical axis 14 of the ultrasonic actuator 1 - by the angle A/n or 2TT/n.
  • the traveling and standing waves they generate are also shifted from one another by the angle A/n or 2TT/n.
  • each generator for a planar traveling wave or in each traveling wave generator 12 the active generators for a planar standing wave or the standing wave generators 13 of one and the same standing wave can be in phase or out of phase with one another.
  • the electrical alternating voltages U1 to Un generated by the generators 17, not shown in FIG. have a trapezoidal shape or any other shape. It is advantageous if the amplitudes of these voltages are the same.
  • the phases of these voltages U1 to lln are preferably around the angle +/-90 0 (TT/2) or around the angle +/-120 0 (2TT/3)) or another angle 2TT/n, which results from the number n is determined, which indicates the number of active standing wave generators 13 of which each traveling wave generator 12 consists, shifted from one another.
  • FIG. 20 shows a possible embodiment of a generator 13 for a planar standing wave or a standing wave generator 13.
  • This has a three-layer structure which consists of an excitation electrode 79, a general electrode 80 and a polarized piezoelectric ceramic layer 81 between them.
  • the arrows shown in FIG. 20 indicate the direction of polarization of the piezoceramic layer 81.
  • the generator 13 has a multilayer structure with alternately arranged layers of the excitation electrode 79, the general electrode 80 and the piezoceramic 81 between them.
  • the arrows in Fig. 21 indicate the polarization direction of the piezoceramic layers 81, whereby the polarization directions of adjacent generators 13 can be directed in the same direction or differently.
  • the voltage supply to the ultrasonic motor according to the invention can take place with a lower voltage.
  • Illustrations a) to d) show the maximum deformations of the polygonal plate calculated using FEM with the corresponding wave formation.
  • the Excitation of other planar modes is possible, as is the excitation of the above-mentioned standing waves of a higher order.
  • the frictional contact between the drive element 6 and the element 2 to be driven causes the element 2 to be driven to rotate in the direction indicated by arrow 26.
  • the representation b) is the corresponding side view to the representation a) of Fig. 24.
  • the arrow 27 indicates the direction of the longitudinal movement of the element 2 to be driven, which results from the rotation of the same.
  • 25 illustrates a possible electrical connection of the ultrasonic actuator 1 or the polygonal plate 4 of the ultrasonic motor according to the invention according to FIG a movement of the element 2 to be driven via the changeover switch 25 to either the first or the second active standing wave generator 13.
  • the frequency of the generator 17 corresponds to the frequency of the longitudinal standing wave to be excited in the polygonal plate 4 in the direction of its diagonal.
  • the change in the direction of movement of the element 2 to be driven takes place by actuating the switch 25.
  • the phase shift between the voltages U1, U2 for generating a traveling wave is 120 ° (2K/3) and their amplitudes are the same .
  • the change in the direction of movement of the element 2 to be driven takes place by actuating the switch 25. It is also possible to reverse the direction of movement by changing the phase shift between the voltages U1, U2 by ⁇ 120°.
  • standing waves or eigenmodes in various geometric bodies is defined by boundary conditions.
  • Features such as angles, surfaces, openings, etc. represent the most important boundary conditions for the appearance (ie the eigenform) of the standing waves (ie the modes) that occur in a geometric body. Therefore, the eigenmodes belonging to a geometric body are specific and characteristic of it.
  • Planar eigenmodes of plates or disks represent a subset of standing waves in which the oscillation of the material points of the body occurs mainly in the plane of the plate.
  • the oscillation amplitudes in a direction perpendicular to the large plate sides are at least an order of magnitude smaller than in the other two directions perpendicular to them and do not arise directly due to the wave process, but are caused by transverse contractions as a side effect of the waves propagating within the plane of the plate.
  • Planar eigenmodes have a high coupling factor.
  • Their piezoelectric excitation is very efficient, i.e. it A high proportion of the electrical energy is converted into the mechanical energy of the vibrations.
  • the piezoelectric ultrasonic actuator 1 designed as a polygonal plate 4 has two generators 13 for generating standing waves.
  • the electrical excitation device 3 generates an alternating electrical voltage with a sine, triangular, rectangular or any other shape, the main harmonic of which corresponds to the resonance frequency or close to the resonance frequency of the first or second mode of the acoustic longitudinal standing wave, which is longitudinal to the diagonal 24 of the polygonal plate 4 spreads, lies.
  • an acoustic longitudinal standing wave is generated in the polygonal plate 4, which propagates along its diagonal 20.
  • the ultrasonic actuator 1 or the polygonal plate 4 begins to vibrate in the form shown in Figures 2a) and 2b).
  • the point 22 lying below the intersection of the diagonals 24 on the inner peripheral surface of the polygonal plate 4 moves on an elliptical movement path 22 inclined at an angle a to the plane P2 (see Figures 2c) and 2d)).
  • the drive element 6 Since the drive element 6 is thin-walled and is acoustically rigidly connected to the polygonal plate 4, the nearby points on the thread surface also move along a tangential elliptical path. Because of the eccentric arrangement of the opening 5, this movement of the drive element 6 creates a friction force which gives the element 2 to be driven a torque.
  • the shape of the deformation of the standing wave used is determined by the boundary conditions of the polygonal plate 4, ie by its outer surfaces, angles and its inner opening 5.
  • the wave generated represents a planar standing wave in which the oscillation amplitude of the polygonal plate 4 in the axial direction is more than an order of magnitude smaller than the oscillation amplitude in the directions perpendicular to it, ie in the directions parallel to the large main sides.
  • the vibrations of the material points mainly take place in the plane of the polygonal plate 4.
  • the change in the direction of propagation of the traveling wave leads to a change in the direction of rotation of the element 2 to be driven and to a change in the axial direction, i.e. the longitudinal displacement.
  • the drive element 6 is thin-walled, that is, its thickness t is significantly smaller than the width of the polygonal plate 4 in the radial direction, the vibration of the ultrasonic actuator 1 is only slightly disturbed or changed by the drive element connected to it. Therefore, the electromechanical coupling coefficient of the ultrasonic actuator is determined by the electromechanical coupling coefficient of the polygonal plate 4. This means that the electromechanical coupling coefficient of the ultrasonic actuator 1 is maximized in the ultrasonic motor according to the invention. This significantly increases its vibration speed and thus the maximum possible load on the ultrasonic actuator 1, which also results in an increased holding force of the ultrasonic motor according to the invention. [00127] List of reference symbols

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  • General Electrical Machinery Utilizing Piezoelectricity, Electrostriction Or Magnetostriction (AREA)

Abstract

L'invention concerne un moteur à ultrasons comprenant : au moins un actionneur ultrasonique piézoélectrique (1) comportant au moins un générateur (12) pour générer une onde progressive acoustique plane ; un élément (2) à entraîner ayant un filetage externe ; et un élément d'entraînement (6) ayant une surface périphérique interne (7), pourvue d'un filetage (8), et une surface périphérique externe, l'élément d'entraînement étant inséré dans l'actionneur ultrasonique (1) de sorte qu'une surface périphérique interne dudit actionneur entoure la surface périphérique externe de l'élément d'entraînement (6), l'élément (2) à entraîner et l'élément d'entraînement (6) étant en prise avec le filetage, et l'onde acoustique plane pouvant être transmise de l'actionneur ultrasonique (1) à l'élément d'entraînement (6), entraînant ainsi la rotation de l'élément (2) à entraîner. L'actionneur ultrasonique (1) a la forme d'une plaque polygonale (4) comportant deux grandes surfaces principales (19) et au moins trois surfaces latérales moins importantes (18) qui relient les deux surfaces principales (19) l'une à l'autre, et l'actionneur comprend au moins un générateur actif (13) pour générer une onde acoustique stationnaire plane dont la vitesse d'oscillation maximale se situe dans la région de la surface périphérique interne de l'actionneur ultrasonique (1).
PCT/DE2023/100444 2022-06-13 2023-06-13 Moteur à ultrasons WO2023241759A1 (fr)

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