Piezoelectric inertial driver

Abstract

The invention relates to a piezoelectric inertial driver (1) comprising: a drive device (2) with a drive element (5) comprising a contact element (9, 10) with an inner circumferential surface (4) with a thread (3); an element (6) to be driven having an outer circumferential surface (8) provided with a thread (7); and an electrical excitation device (16) for electrically controlling the drive device (2), the element (6) to be driven being in threaded engagement with the drive element (5). The contact elements (9, 10) are arranged symmetrically with respect to a virtual diametric separation plane (P) and at least partially surround the element (6) to be driven, the contact elements (9, 10) being connected directly or indirectly to the base element (14) and connected to each other, and the drive device (2) has at least two multi-layer piezoelectric actuators (11) having a virtual actuator longitudinal axis (19), according to the invention, the multi-layer piezoelectric actuators (11) are arranged with a respective first side (12) on the base element (14) and with a respective other side (13) opposite the first side (12) on the respective contact elements (9, 10), and the electrical excitation device (16) comprises at least two generators (17, 18) which provide a voltage for exciting the piezoelectric actuators (11).

Description

Technical Field

[0001] The invention relates to a piezoelectric inertia driver. Background Art

[0002] Piezoelectric inertia drives are known from the prior art, in which the friction contact is implemented in the form of a threaded engagement. Piezoelectric inertia drives can be used, for example, as spindle drives in various types of mechanisms, for example in linear drives, in precision sealing and metering devices, in valves, in precision cutting drives, in control drives, in precision positioning devices, for example in technical coordinate tables, in multi-coordinate positioning devices, in tripods or hexapods, in optical laser systems and similar devices, and in precision medical devices, for example pumps, syringes, insulin pumps or devices for bone lengthening.

[0003] Lasers are used in many areas of technology, whether in metrology, medical technology, metal processing, etc. Often, in this case, the laser beam is precisely steered or guided with the aid of tilting mirrors. The required precision for steering the laser beam is achieved with the aid of micrometer screws. These micrometer screws are usually actuated manually. However, in many applications, manual adjustment of the tilting mirrors is not possible or desirable, for example in vacuum chambers, in photolithography machines or in velocimeters.

[0004] Inertia-based piezoelectric drives are often used for automatic positioning of tilt mirrors. In an inertial drive, the element to be driven, i.e., a rotor or roller, is connected or coupled to a piezoelectric actuator via friction contact. The motion process of such an inertial drive consists of two phases: in the first phase, the piezoelectric actuator slowly stretches and transmits the corresponding motion to the element to be driven due to static friction. In the second phase following the first phase, a rapid contraction of the actuator occurs. In this case, the element to be driven cannot follow the rapid motion of the actuator and remain in its position due to its inertia. Here, a relative motion (slip) occurs between the actuator and the element to be driven, i.e., the actuator slides over, and sliding friction occurs in the friction contact. Of course, the time course of the two aforementioned phases can be exchanged, so that in the first phase, a rapid stretch occurs with relative motion or sliding between the actuator and the element to be driven without a driving motion, and in the second phase, a slow contraction of the actuator occurs, in which the follow-up of the element to be driven occurs due to static friction and thus a corresponding driving motion is performed.

[0005] DE 10 202 111 3 751 A1 of the applicant describes a drive device for driving a spindle, which comprises two actuator devices, wherein the actuator devices act on an actuating device and a frame device and achieve the driving of the spindle by providing corresponding abutment surface sections for contacting the spindle at two different contact points.

[0006] Document US2011 / 0109197A1 discloses a drive device having a drive shaft surrounded by a rotatably supported drive element, wherein a plurality of contact elements evenly distributed on the circumference are pressed onto the drive shaft. The drive element is set in a rotational motion by two diametrically opposed actuators that perform drive motions in the same direction, and the rotational motion is transmitted to the drive shaft via the contact elements. A stick-slip drive method is generated by applying a sawtooth voltage to the actuator, by which a continuous rotational motion of the drive shaft can be achieved.

[0007] EP1396012B2 teaches a piezoelectric driver having a piezoelectric element coupled to a resonator having a horn, wherein vibrations suitable for driving are transmitted from the piezoelectric element to the resonator and in particular the horn, which in turn can be pressed against the surface of the element to be driven, and the vibrations of the horn produce drive of the element to be driven.

[0008] DE 10 2010 022 812 B4 describes an ultrasonic motor having an annular ultrasonic actuator for generating traveling waves, which are transmitted to a contact element arranged on the inner circumference of the ultrasonic motor and threadedly engaged with a threaded rod to be driven, thereby generating a rotational movement of the threaded rod.

[0009] Document DE 199 09 913 A1 discloses an electromechanical drive device having a rotor to be driven and supported in a bearing device and a piezoelectric element, wherein the bearing device has a rotor receiving portion which can be driven by the piezoelectric element.

[0010] A piezoelectric inertia drive for rotating a driven element in the form of a spindle is known from US Pat. No. 5,410,206 A. Here, the spindle is gripped on both sides by means of a piezoelectric drive in the form of two threaded jaws and brought into frictional contact with them. One of the two jaws is connected to a piezoelectric actuator, which sets the threaded rod into motion or rotation based on the inertia principle. The second jaw presses the threaded rod onto the first clamp and thereby supports the threaded rod.

[0011] The main disadvantage of the spindle drive of US5410206A is that the drive motion is different for the two directions of rotation of the spindle, since the piezoelectric actuator behaves differently with respect to extension and contraction. As a result, the drive has different characteristics in the two drive directions, resulting in different step widths and travel speeds in the different directions of rotation of the spindle. In order to linearize the drive characteristics, special adjustment measures are required in the drive electronics. Another disadvantage is that the second clamping jaw brakes the spindle, which leads to a reduction in the efficiency of the drive device. Summary of the invention

[0012] The object of the present invention is therefore to provide a piezoelectric inertia drive, in particular for driving a spindle, which has symmetrical drive characteristics and thus drives the spindle identically and preferably equally in both rotational directions when the spindle is used as the element to be driven, and which also has a high efficiency, making it possible to reduce the drive power.

[0013] This object is achieved by a piezoelectric inertia drive according to claim 1 , wherein the subsequent dependent claims describe at least advantageous developments.

[0014] If, as mentioned above and where appropriate also below, an indefinite article is used in connection with a feature in this text, reference should be made to the quantity indication implied by the indefinite article when subsequently referring to the same feature by using the definite article, without this in any way limiting the quantity indication accordingly.

[0015] The piezoelectric inertia driver according to the present invention comprises a driving device having a driving element, the driving element having a contact element, wherein each contact element has an inner circumferential surface, and the inner circumferential surface has a thread. The piezoelectric inertia driver according to the present invention also comprises a driven element having an outer circumferential surface provided with a thread, and an electric excitation device for electrically controlling the driving device, wherein the driven element is threadedly engaged with the driving element.

[0016] The contact elements are arranged symmetrically relative to a virtual diameter separation plane and at least partially surround the element to be driven, wherein the contact elements are directly or indirectly connected to the base element and are additionally connected to each other, and the drive device has at least two piezoelectric actuators and preferably multilayer piezoelectric actuators, which have a virtual actuator longitudinal axis, and are arranged on the base element with a corresponding first side and on the corresponding contact element with a corresponding other side opposite to the first side, and the electrical excitation device includes at least two generators, which provide voltage for exciting the piezoelectric actuators.

[0017] By symmetrically arranging the contact elements or piezoelectric actuators, a symmetrical and identical drive of the drive element or contact element is achieved, thereby achieving substantially identical speeds and substantially identical step widths of the element to be driven in both directions of rotation. The contact elements not only support or bear against the element to be driven, but also participate in driving or propelling the element to be driven. Therefore, no contact element brakes the element to be driven, so that the efficiency of the piezoelectric inertia drive according to the invention is correspondingly high.

[0018] According to the invention, the contact elements of the drive element are connected to each other via elastic elements and to two or four elastic elements of the carrier of the base element by means of connecting elements, wherein the piezoelectric actuator is biased in the axial direction by means of the elastic elements of the carrier of the base element by means of the connecting elements. The elastic elements for connecting the contact elements of the drive element allow a torque to be formed that acts on the element to be driven when the piezoelectric actuator is driven and deforms accordingly. The elastic elements of the carrier of the base element allow the piezoelectric actuator to be biased in the axial direction by means of the connecting elements. In the presence of four elastic elements of the carrier, a symmetrical structure is produced, which counteracts or compensates for any bending of the carrier.

[0019] It may be advantageous if each virtual actuator longitudinal axis is arranged parallel to the virtual diametrical separation plane (P). As a result, the force acting on the contact element may be maximized.

[0020] It can also be advantageous if the piezoelectric inertia drive has elastic elements which are connected to the base element and by means of which the contact element is pressed onto the element to be driven. By connecting the elastic elements to the base element, a lever effect and a torque generation on the element to be driven is achieved. In addition, the connection of the elastic elements to the base element absorbs possible adverse external forces acting perpendicularly to the longitudinal axis of the actuator.

[0021] It can also be advantageous that the drive device comprises an elastic element, by which the contact element is pressed onto the element to be driven. By means of such an elastic element, a force acting perpendicularly to the longitudinal axis of the element to be driven can be applied, which force presses the contact element onto the element to be driven.

[0022] It may also be advantageous if the base element has two movable elements and two elastic elements, by means of which the contact element is pressed onto the element to be driven.

[0023] It can also be advantageous if the drive element has an elastic element, by means of which the corresponding piezoelectric actuator is biased in the axial direction. It can be particularly advantageous here if the drive element also has a connecting element, by means of which the corresponding piezoelectric actuator is biased in interaction with the elastic element, thereby achieving an increased bias. In particular, piezoelectric multilayer actuators require an axial bias so that delamination of the layers does not occur.

[0024] The present invention also relates to a piezoelectric inertia drive, comprising: a drive device having a drive element, the drive element comprising a contact element having an inner circumferential surface with a thread; an element to be driven having an outer circumferential surface provided with a thread; and an electrical excitation device for electrically controlling the drive device, wherein the element to be driven is threadedly engaged with the drive element, and the contact element is symmetrically arranged relative to a virtual diameter separation plane and at least partially surrounds the element to be driven, wherein the contact element is directly or indirectly connected to a base element, and the drive device has at least two multilayer piezoelectric actuators, which have a virtual actuator longitudinal axis, which are arranged on the base element with a corresponding first side and on the corresponding contact element with a corresponding other side opposite to the first side, and the electrical excitation device includes at least two generators, which provide voltages for exciting the piezoelectric actuators, wherein the drive element is implemented as a two-piece element and is connected to two or four elastic elements of a carrier of the base element by means of a connecting element, and the piezoelectric actuator is biased in the axial direction by the elastic element by means of the connecting element. In the case of such a drive device, a greater advancement amplitude of the element to be driven can be achieved.

[0025] It may be advantageous if the driven element is implemented as a hollow threaded rod and the corresponding cavity is filled with a sound absorbing material, thereby reducing parasitic vibrations that may occur in the driven element, thereby improving the driving function of the piezoelectric inertia drive.

[0026] It can also be advantageous if the thread of the element to be driven or the thread of the contact element is made of a wear-resistant material or is provided with a wear-resistant layer, thereby reducing wear and extending the service life. It is also conceivable that the element to be driven or the contact element is made of a wear-resistant material.

[0027] It can prove advantageous if the piezoelectric inertia drive has a pressing device, with which the element to be driven is pressed against the drive element, and the drive element acts directly or indirectly on the element to be driven in the axial direction. This achieves a higher contact force, from which a greater torque of the piezoelectric inertia drive is generated.

[0028] Furthermore, it can prove advantageous if the piezoelectric inertia drive has two or more drive devices which act on a common element to be driven, wherein the drive devices are fixed to one another by elastic elements. The use of a plurality of drive devices increases the driving force of the piezoelectric inertia drive. In this case, the elastic elements prevent the movement of the drive devices in directions pointing toward one another, but allow movement in other degrees of freedom. This prevents wedging of the element to be driven, in particular when the element to be driven is in the form of a threaded rod or a spindle.

[0029] Furthermore, it may prove advantageous if the electrical excitation device is designed to generate two complementary sawtooth voltages U1 , U2 in order to excite the piezoelectric actuator. This results in a particularly efficient operation of the piezoelectric inertia drive. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] The advantages and practicality of the present invention will become more apparent from the following description of preferred embodiments based on the accompanying drawings. In the accompanying drawings:

[0031] Figure 1 shows a perspective view of a piezoelectric inertia actuator not belonging to the present invention;

[0032] Figure 2 Shown according to Figure 1 A three-dimensional diagram of a driving device of a piezoelectric inertia actuator;

[0033] Figure 3 shows a perspective view of a multilayer actuator for a piezoelectric inertia drive according to the present invention;

[0034] Figure 4 A perspective view of a drive device not belonging to the present invention is shown;

[0035] Figure 5 A perspective view of a drive device not belonging to the present invention is shown;

[0036] Figure 6 a) shows two different perspective views of an embodiment of a drive device of a piezoelectric inertia drive according to the invention; Figure 6 b) shows the Figure 6 a) Exploded view of the drive device;

[0037] Figure 7 a) shows two different perspective views of another embodiment of a drive device of a piezoelectric inertia drive according to the invention; Figure 7 b) shows the Figure 7 a) Exploded view of the drive device;

[0038] Figure 8 Two different perspective views showing another embodiment of a drive device of a piezoelectric inertia drive according to the invention;

[0039] Fig. 9 a) to Fig. 9 c) shows different embodiments of the element to be driven of the inertial drive in the form of a threaded rod according to the invention;

[0040] Fig.10 a), Fig.10 b) shows a different perspective view of a piezoelectric drive having two drive devices not belonging to the invention and a known element to be driven;

[0041] Fig.11 , Fig.12 Different embodiments of a piezoelectric drive according to the invention are shown, with two drive devices and a common element to be driven;

[0042] Fig.13 a) shows the principle structure of the electric excitation device of the piezoelectric inertia drive according to the present invention; Fig.13 b) shows that according to Fig.13 a) a graph showing the time curve of the voltage generated by the excitation device and the resulting movement of the element to be driven;

[0043] Fig.14 a) to Fig.14 d) shows the control of the actuator to generate a clockwise or counterclockwise driving motion of the driven element according to Figure 2 , Figure 5 , Figure 6 and Figure 8 The maximum deformation of the drive device calculated using the finite element method (FEM). DETAILED DESCRIPTION

[0044] Figure 1 The piezoelectric inertia drive 1 shown and not belonging to the present invention has a driven element 6 in the form of a spindle, which is provided with a spiral, and an electrical excitation device 16. The inertia drive 1 contains a drive device 2 driven by two multilayer piezoelectric actuators 11. The drive device is divided by an imaginary diametrical plane P, which extends through the center or axis of the element 6 to be driven.

[0045] The drive device 2 has a drive element 5, which has two contact elements 9, 10 arranged symmetrically with respect to a diameter plane P, and the two contact elements 9, 10 are integrally or monolithically formed with the drive element 5. Each of the contact elements 9, 10 has an inner circumferential surface 4 provided with a thread. The two contact elements 9, 10 clamp or contact the element to be driven 6 from both sides, and the element to be driven 6 is frictionally engaged with the threads of the two contact elements 9, 10. Each piezoelectric actuator 11 is supported on a base element 14 with a side 12. The other and opposite side 13 of the corresponding piezoelectric actuator 11 is connected to the corresponding contact element 9, 10 of the drive element 5. It is conceivable that the piezoelectric actuator 11 is fixed to the base element 14 with the side 12 by bonding. Each contact element 9, 10 has two elastic sections 20.

[0046] The excitation device 16 includes two generators 17, 18, which generate complementary sawtooth voltages U1, U2. The excitation device 16 is electrically connected to the piezoelectric actuator 11 via an electrical connection 21 provided on the actuator. By controlling the actuator of the drive device with the electrical excitation device 16, the element 6 to be driven is directly placed in a rotational motion and indirectly placed in a translational motion. The element 6 to be driven can be equipped with an adhesive bag 25 for filling with an adhesive in order to additionally fix the piezoelectric actuator 11.

[0047] Figure 2 A single diagram shows the Figure 1 A drive device 2 of a piezoelectric inertia drive 1. The drive device 2 includes a drive element 5 and a piezoelectric multilayer actuator 11. The drive device 2 is divided into two identical symmetrical halves by a virtual diameter plane P. The contact elements 9, 10 integrally formed with the drive element 5 each have an inner circumferential surface 4 provided with a thread. The piezoelectric actuator is supported on a base element 14 of the drive element 5 with a side 12 and is connected to the drive element 5 with another opposite side. The support point is located between the two actuators. Their virtual longitudinal axes 19 extend parallel to the virtual diameter plane P. The piezoelectric actuator has an electrical connector 21. The fastening hole 23 is used to screw the drive device 2 onto a substrate or a device housing. The fastening hole 24 is used to fix Figure 2 Elastic elements not shown. In addition, the drive element 5 has four elastic sections 20. The elastic sections allow the contact elements 9, 10 to be pressed onto the element to be driven 6. An optional elastic element 27 in the form of a helical spring can be placed in the hole 22, which pulls the contact elements 9, 10 together or toward each other and thus presses the contact elements 9, 10 onto the element to be driven.

[0048] Figure 3 A multilayer piezoelectric actuator 11 is shown for use in a piezoelectric inertia drive according to the invention. The individual actuator layers 26 each have electrodes on their large surfaces and a piezoelectric material arranged between them. All adjacent layers 26 have an opposite electrical polarization indicated by arrows P. The equipolar electrodes are connected to each other and to the electrical connection 21.

[0049] Figure 4 A drive device 2 is shown which is not an inertial drive of the present invention. In this embodiment variant of the drive device 2, the two contact elements 9, 10 of the drive element 5 are connected by a spring element in the form of a helical spring 27 and are thus pressed onto the element to be driven 6. Other forms of the spring element are conceivable, for example in the form of a flat spring. Figure 4The drive element 5 of the embodiment variant shown also has an elastic element 30 and a movable element 31, which presses the contact elements 9, 10 onto the element to be driven. In addition, each contact element 9, 10 has an elastic element 28. The elastic element 28 allows the piezoelectric actuator to be biased in the axial direction. The additional biasing force is achieved by means of a connecting element 29 in the form of a screw.

[0050] Figure 5 Another drive device 2 of an inertial drive 1 which is not part of the present invention is shown. In this embodiment variant of the drive device 2, the two contact elements 9, 10 of the drive element 5 each have an elastic element 32. The elastic element 32 is connected to an elastic element 33. The elastic elements 32, 33 allow the contact elements 9, 10 to be pressed onto the element to be driven. The contact elements 9, 10 are connected to the base part 14 via the elastic elements 32, 33.

[0051] Figure 6 a) shows two different perspective views of an embodiment of a drive device 2 of a piezoelectric inertia drive 1 according to the invention. Here, the contact elements 9, 10 of the drive element 5 are connected to one another via elastic elements 34. The base element 14 has two carriers 35, via which the drive element 5 is connected to the base element 14 by means of connecting elements 36. The carriers 35 have elastic sections 37, which allow the piezoelectric actuator 11 to be biased in the axial direction or along its imaginary longitudinal axis. Figure 6 b) shows the corresponding exploded view according to Figure 6 a) driving device 2.

[0052] Figure 7 a) shows two different perspective views of another embodiment of the drive device 2 of the piezoelectric inertia drive 1 according to the invention. Here, the contact elements 9, 10 of the drive element 5 are connected to each other via elastic elements 34. The base element 14 has four carriers 35, via which the drive element 5 is connected to the base element 14 by means of connecting elements 36. The carriers 35 have elastic sections 37, which allow the piezoelectric actuator 11 to be biased in the axial direction. Figure 7 b) shows the corresponding exploded view according to Figure 7 a) driving device 2.

[0053] Figure 8Two different perspective views of an alternative embodiment of a drive device 2 of a piezoelectric inertia drive 1 according to the invention are shown. In this case, the drive device 2 has a two-part drive element 15. The contact elements 9, 10 of the drive element 15 are not connected to one another. The base element 14 has two carriers 35, via which the drive element 15 is connected to the base element 14 by means of connecting elements 36. The carriers 35 have elastic sections 37, which allow the piezoelectric actuator 11 to be biased in the axial direction.

[0054] Fig. 9 a) to Fig. 9 c) shows different embodiments of the driven element 6 of the inertial drive 1 according to the invention in the form of a threaded rod. Fig. 9 a), the element to be driven 6 is designed as a solid threaded rod 38 made of a hard and wear-resistant material, such as heat-treated steel, oxide or cermet. Fig. 9 b) or Fig. 9 c) The element 6 to be driven can be designed as a hollow threaded rod 40, wherein the corresponding inner hole 41 has a circular shape. However, other geometric shapes of the inner opening are also conceivable, for example a polygon. Fig. 9 c), a rod 42 made of a sound-absorbing material can be inserted into the opening 41 of the hollow threaded rod 40. Such a rod 42 is implemented using an elastic material, such as rubber. Here, the elastic material can be filled with hard particles, such as metal particles. In addition, it is also conceivable that the rod 42 consists of a viscoelastic material, such as a thermoplastic material, wherein the viscoelastic material can be filled with particles, such as metal and / or rubber particles. In addition, the rod 36 can also consist of a hard porous material, such as a porous oxide ceramic, whose pores are filled with a viscous material. Various other materials or material mixtures with a high sound absorption coefficient can be conceived for the rod 43. For example, the rod 42 can also be made of a hard material, such as steel, oxide ceramic, metal ceramic, wherein a layer of sound-absorbing material 43 (such as rubber, epoxy resin, etc.) is arranged between the rod 42 and the drive element 5.

[0055] Fig.10 a) and Fig.10 b) shows a different perspective view of a piezoelectric inertia drive 1 not belonging to the invention, which has a Figure 2 , Figure 4 and Figure 5The two drive devices 2 and the common element 6 to be driven are arranged in a manner similar to that of the embodiment of the present invention. The drive devices 2 are kept at a distance from each other by means of elastic elements 44. The elastic elements 44 are fixed to the base element 14 by means of fastening elements in the form of countersunk screws screwed into holes 45. It is also conceivable to fasten the drive devices 2 to each other by means of flat elastic elements in the form of leaf springs. The fastening holes 46 serve to fasten the piezoelectric inertia drive to a base body or a device housing. It is conceivable to use three or more drive devices 2 instead of the two drive devices shown here.

[0056] Fig.11 An embodiment of the piezoelectric inertia drive 1 according to the present invention is shown. The piezoelectric inertia drive 1 has a Figure 6 The two drive devices 2 and the common element to be driven 6 are provided. The drive devices 2 are kept at a distance from each other by means of elastic elements 44. The elastic elements 44 are fixed to the base element 14 by means of fastening elements in the form of countersunk screws screwed into holes 45. It is conceivable to use three or more drive devices 2 instead of the two drive devices shown here.

[0057] Fig.12 Another embodiment of the piezoelectric inertia drive 1 according to the present invention is shown. The piezoelectric inertia drive 1 has a Figure 7 The two drive devices 2 and the common element to be driven 6 are provided. The drive devices 2 are kept at a distance from each other by means of elastic elements 44. The elastic elements are fixed to the base element 14 by means of fastening elements in the form of countersunk screws screwed into holes 46. It is conceivable to use three or more drive devices 2 instead of the two drive devices shown here.

[0058] Fig.13 a) illustrates the principle structure of the electric excitation device of the piezoelectric inertia drive according to the present invention. The excitation device can be constructed in a microcontroller, in an FPGA or by discrete integrated circuits. The excitation device includes a phase accumulator (PA) 47, a pulse width modulator or a pulse density modulator (PWM or PDM) 48, a switching power output stage (SPS) 49, a low-pass filter (LP) 50, a current sensor 51 and a current regulation unit 52.

[0059] The phase accumulator 47 represents an increasing or decreasing n-bit register that generates a linearly increasing or decreasing binary number. The PWM or PDM 48 modulates the pulse width or pulse density of the high-frequency rectangular carrier signal according to the binary number (ramp function) generated by the PA 47. The frequency fcar of the carrier signal is preferably 10 times higher than the frequency fexc at which the piezoelectric actuator is excited. The ramp-function modulated rectangular carrier voltage is further amplified by the SPS 49 and forwarded to the piezoelectric actuator 11 via the LP (50). The generators 17, 18 are two transistor bridges or half-bridge circuits within the switching power output stage 49. The current of the actuator 11 is measured by a current sensor (CS) 51, compared with a reference signal and forwarded to a current regulation unit (CUU) 52. The current regulation unit (CCU) 52 regulates the current according to the specified reference signal and thus influences the extension of the piezoelectric actuator.

[0060] Fig.13 b corresponds to the activation of the excitation device 16 according to Fig.13 a The time curve of the generated voltages U1 , U2 and the resulting movement S of the element 6 to be driven.

[0061] The piezoelectric drive of the inertial motor according to the invention is controlled in four time periods with two AC voltages U1, U2 of the same amplitude but different polarity. While in the first time period within the time t1, the voltage U1 of the generator 17 rises linearly with a slope Kup to a maximum value U1max (ramp function), the voltage U2 of the generator 18 has the same but negative slope or gradient -Kup, i.e. it drops to a negative maximum value -U2max. In the second time period, i.e. within the time t2, the amplitudes of the two voltages U1, U2 remain unchanged. Afterwards, the voltage U1 drops with a slope -Kdw within the time t3, and the voltage U2 rises with Kdw. Within the time t4, the amplitudes of the voltages U1, U2 are zero. The frequencies fexc of the AC voltages U1, U2 are equal and are tens of kHz. The rise time t1 is significantly smaller than the fall time t3.

[0062] Fig.14 a) to Fig.14 d) shows the control of the actuator to generate a clockwise or counterclockwise driving motion of the driven element according to Figure 2 , Figure 5 , Figure 6 and Figure 8 The maximum deformation of the drive unit calculated using FEM. Here, Fig.14 a) shows that according to Figure 2 The corresponding deformation of the case of the drive device 2, Fig.14 b) shows that according to Figure 5 The corresponding deformation of the case of the drive device 2, Fig.14 c) shows that according to Figure 6The corresponding deformation of the case of the drive device 2, and Fig.14 d) shows that according to Figure 8 The corresponding deformation of the driving device in the case.

[0063] The piezoelectric inertia drive 1 and its excitation device 16 of the present invention have the following functional mode: the generators 17, 18 of the excitation device 16 generate two sawtooth voltages U1, U2 with the same time curve, equal voltage and different polarity (see Fig.13 ). The time curve of the voltages U1, U2 has two ranges t1, t3, which have different slopes. In the first range t1, the slope is small. In this range, the amount of the voltages U1, U2 increases slowly to the final value U1max, U2max. In the second range with a large slope t3, the amount of the voltages U1, U2 decreases very quickly. The difference is preferably an order of magnitude. In addition, in the time curve of the voltages U1, U2, there can be two further ranges t2, t4, in which the amount of the voltages U1, U2 remains unchanged.

[0064] To excite the piezoelectric inertia actuator 1, at t = 0 (see Fig.12 b) Applying voltages U1, U2 to each piezoelectric actuator 11. As a result, the actuator to which positive voltage U1 is applied slowly stretches, while the actuator to which negative voltage U2 is applied contracts. By the extension or contraction of the actuator, the drive element 5 of the drive device 2 connected to the actuator experiences Fig.14 The inner circumferential surface 4 of the driving element 5, which is in frictional engagement with the driven element 6, imparts rotation to the driven element 6 due to the static friction therebetween. Here, the direction of rotation depends on the polarity of the voltage U1, U2 or the deformation direction of the actuator and is Fig.13 In a), it is indicated by an arrow.

[0065] After the stage of small slope t1, stage t2 can be carried out, in which the actuator voltage remains unchanged and the element to be driven 6 is at rest. In the subsequent stage of large slope t3, the amount of voltage U1, U2 decreases very rapidly. The actuator follows the voltage and changes its deformation direction at the same time. That is, the previously stretched actuator contracts, and the contracted actuator stretches. Since the element to be driven is affected by mass, it cannot follow the movement of the actuator or the movement of the drive element and remain in its position due to inertia. Due to the force generated in the friction contact, static friction is converted into sliding friction. The surfaces of the friction contact between the drive element and the element to be driven slide against each other. Then comes stage t4, in which the voltages U1, U2 are zero and the element to be driven is stationary. The motion process is repeated periodically at a frequency of up to several kHz. The element to be driven is directly placed in a rotational motion and indirectly placed in a linear motion. In order to reverse the direction of motion of the element to be driven, the voltages U1, U2 are exchanged.

[0066] Description of reference numerals:

[0067] 1 Piezoelectric Inertia Actuator

[0068] 2 Drive device

[0069] 3 (Inner circumferential surface 4) thread

[0070] 4 Inner circumferential surface

[0071] 5, 15 Driving elements

[0072] 6 Components to be driven

[0073] 7 Thread (of the driven element 6)

[0074] 8 Outer circumferential surface (of the driven element 6)

[0075] 9, 10 Contact element (of driving element 5)

[0076] 11 Multilayer Piezoelectric Actuator

[0077] 12, 13 (Side of the multilayer piezoelectric actuator 11)

[0078] 14 Base element

[0079] 16. Incentive device

[0080] 17, 18 Voltage generator

[0081] 19 Virtual longitudinal axis

[0082] 20 Elastic element

[0083] 21 Electrical connections for actuator

[0084] 22 Spring hole

[0085] 23 Fastening holes

[0086] 24 Fastening holes for elastic elements

[0087] 25 Adhesive Bags

[0088] 26 Piezoelectric layer (of actuator 11)

[0089] 27, 28 Elastic element

[0090] 29 Connecting elements

[0091] 30 Elastic element

[0092] 31 Movable elements

[0093] 32, 33, 34 elastic elements

[0094] 35 (of the base element 14) carrier

[0095] 36 Connecting elements

[0096] 37 Elastic element

[0097] 38 Threaded rod

[0098] 39 Actuated element in the form of a single rod

[0099] 40 Hollow Threaded Rod

[0100] 41 Axial opening in the element to be driven

[0101] 42 Sound absorbing rod

[0102] 43 Sound absorbing material layer

[0103] 44 Elastic element

[0104] 45, 46 Fastening holes

[0105] 47 Phase Accumulator (PA)

[0106] 48 Pulse Width Modulator or Pulse Density Modulator (PWM or PDM)

[0107] 49 Switching Power Output Stage (SPS)

[0108] 50 Low pass filter (LP)

[0109] 51 Current sensor

[0110] 52 Current Control Unit (CCU)

Claims

1. A piezoelectric inertia actuator (1), comprising: A drive device (2) having a drive element (5), the drive element (5) comprising a contact element (9, 10) having an inner circumferential surface (4), the inner circumferential surface (4) having a thread (3); an element to be driven (6) having an outer circumferential surface (8) provided with a thread (7); and an electric excitation device (16) for electrically controlling the drive device (2), wherein the element to be driven (6) is threadedly engaged with the drive element (5), and the contact elements (9, 10) are symmetrically arranged with respect to a virtual diameter separation plane (P) and at least partially surround the element to be driven (6), wherein the contact elements (9, 10) are directly or indirectly connected to a base element (14) and to each other, and the drive device (2) has at least two multilayer piezoelectric actuators (11), the multilayer piezoelectric actuators (11) having a virtual actuator longitudinal direction. axis (19), the multilayer piezoelectric actuator (11) is arranged on the base element (14) with a corresponding first side (12) and on the corresponding contact element (9, 10) with a corresponding other side (13) opposite to the first side (12), and the electric excitation device (16) includes at least two generators (17, 18), the generators (17, 18) provide a voltage for exciting the piezoelectric actuator (11), characterized in that the contact elements (9, 10) of the drive element (5) are connected to each other by elastic elements (34) and are connected to two or four elastic elements (37) of the carrier (35) of the base element (14) by means of connecting elements (36), wherein the piezoelectric actuator (11) is biased in the axial direction by means of the elastic elements (37) and by means of the connecting elements (36).

2. The piezoelectric inertia actuator (1) according to claim 1, characterized in that Each virtual actuator longitudinal axis (19) is arranged parallel to the virtual diametrical separation plane (P).

3. The piezoelectric inertia actuator (1) according to claim 1 or 2, characterized in that: The piezoelectric inertia driver (1) has an elastic element (20), which is connected to the base element (14) and presses the contact element (9, 10) onto the element to be driven (6) through the elastic element (20).

4. The piezoelectric inertia drive (1) according to any one of the preceding claims, characterized in that The driving device (2) comprises an elastic element (27), and the contact element (9, 10) is pressed onto the element (6) to be driven by the elastic element (27).

5. The piezoelectric inertia drive (1) according to any one of the preceding claims, characterized in that The base element (14) has two movable elements (31) and two elastic elements (30), and the contact elements (9, 10) are pressed onto the element to be driven (6) by the elastic elements (30).

6. The piezoelectric inertia drive (1) according to any one of the preceding claims, characterized in that The drive element (5) has an elastic element (28) by which the corresponding piezoelectric actuator (11) is biased in the axial direction.

7. The piezoelectric inertia actuator (1) according to claim 6, characterized in that The characteristic is that the drive element (5) has a connecting element (29), through which the corresponding piezoelectric actuator (11) is biased in interaction with the elastic element (28).

8. A piezoelectric inertia actuator (1), comprising: A drive device (2) having a drive element (5), the drive element (5) comprising a contact element (9, 10) having an inner circumferential surface (4), the inner circumferential surface (4) having a thread (3); an element to be driven (6) having an outer circumferential surface (8) provided with a thread (7); and an electric excitation device (16) for electrically controlling the drive device (2), wherein the element to be driven (6) is threadedly engaged with the drive element (5), and the contact elements (9, 10) are symmetrically arranged with respect to a virtual diameter separation plane (P) and at least partially surround the element to be driven (6), wherein the contact elements (9, 10) are directly or indirectly connected to a base element (14), and the drive device (2) has at least two multilayer piezoelectric actuators (11), the multilayer piezoelectric actuators (11) having A virtual actuator longitudinal axis (19), the multilayer piezoelectric actuator (11) is arranged on the base element (14) with a corresponding first side (12) and on the corresponding contact element (9, 10) with a corresponding other side (13) opposite to the first side (12), and the electrical excitation device (16) includes at least two generators (17, 18), which provide a voltage for exciting the piezoelectric actuator (11), characterized in that the drive element is implemented as a two-piece element (15) and is connected to two or four elastic elements (37) of the carrier (35) of the base element (14) by means of a connecting element (36), and the piezoelectric actuator (11) is biased in the axial direction by the elastic elements (37) by means of the connecting element (36).

9. The piezoelectric inertia drive (1) according to any one of the preceding claims, characterized in that The element (6) to be driven is implemented as a hollow threaded rod, and the corresponding cavity (26) is filled with a sound absorbing material (28).

10. The piezoelectric inertia drive (1) according to any one of the preceding claims, characterized in that The thread of the element to be driven (6) or the thread of the contact element (9, 10) is made of a wear-resistant material or is provided with a wear-resistant layer.

11. The piezoelectric inertia drive (1) according to any one of the preceding claims, characterized in that The piezoelectric inertia drive (1) has a pressing device, by means of which the element to be driven (6) is pressed against the drive element (5), and the drive element (5) acts directly or indirectly on the element to be driven (6) in the axial direction.

12. The piezoelectric inertia drive (1) according to any one of the preceding claims, characterized in that The piezoelectric inertia drive (1) has two or more drive devices (2) which act on a common element (6) to be driven, wherein the drive devices (2) are fixed to one another by elastic elements (44).

13. The piezoelectric inertia drive (1) according to any one of the preceding claims, characterized in that The electrical excitation device (16) is designed to generate two complementary sawtooth voltages U1, U2 in order to excite the piezoelectric actuator (11).

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