WO2008135353A1

WO2008135353A1 - Piezoelectric drive unit

Info

Publication number: WO2008135353A1
Application number: PCT/EP2008/054545
Authority: WO
Inventors: Walter Haussecker; Vincent Rieger; Jens Twiefel; Tobias Hemsel; Volker Rischmueller; Joerg Wallaschek; Dirk Guenther; Peter Froehlich
Original assignee: Robert Bosch Gmbh
Priority date: 2007-05-07
Filing date: 2008-04-15
Publication date: 2008-11-13
Also published as: DE102007021339A1

Abstract

Disclosed are a piezoelectric drive unit (10) and a method for operating such a drive unit in order to adjust movable parts (11), especially in a motor vehicle. Said piezoelectric drive unit (10) comprises at least one piezo motor (12) that is fitted with a first and a second piezo actuator (18). At least one frictional element (30) of the piezo motor (12) makes it possible to generate a relative movement in relation to a frictional surface (14) located across from the frictional element (30). Only the first piezo actuator is triggered to generate the relative movement in a first direction (13) while only the second piezo actuator is triggered to generate the relative movement in the opposite direction (15).

Description

description

title

Piezoelectric drive device

State of the art

The invention is based on a piezoelectric drive device and a method for operating such according to the preamble of the independent claims.

With WO 00/28652 Al an ultrasonic motor has become known, in which a rotor shaft is rotated by means of ultrasonic vibrators in rotation. In this case, two ultrasonic vibrators are connected at right angles to each other, both vibrators are supplied with an AC voltage such that the two vibrators vibrate to each other with a phase difference. This vibration generates a movement of a plunger that rotates the rotor shaft. A disadvantage of this ultrasonic motor that due to the design and operation of the vibrators many ultrasonic vibrators are necessary to produce sufficient drive torque. Such a motor is therefore very expensive and requires a complex electronic control and a correspondingly large space.

Disclosure of the invention

Advantages of the invention

The piezoelectric drive device according to the invention, as well as the method for operating such a device with the features of the independent claims has the advantage that by controlling only one piezoelectric actuator of a piezo motor whose drive electronics is substantially simplified. The vibration behavior of the piezoelectric motor is determined only by a single excitation frequency, so that the movement path of the plunger is easily predetermined. At outer Influences that detune the resonant frequency, the resonant frequency can be tracked much easier with a single-phase excitation. The non-excited piezoelectric actuator can also be used at the same time as anti-pinch sensor, which converts a mechanical force by the part to be adjusted in an electrical sensor signal.

The measures listed in the dependent claims advantageous refinements and improvements of the embodiments specified in the dependent claims are possible. Due to the single-phase excitation of the piezo motor can be dispensed with a second Elektronikeinheil / Abstimmsschaltung per piezoelectric motor. Only a single excitation signal has to be generated, which is alternately applied to one or the other piezo actuator. This simplifies the signal processing and the coordination of different piezo motors.

Preferably, the piezoelectric actuator is only offset in longitudinal vibrations, so that only

Vibrating components along the longitudinal direction are excited with the largest dimension of the piezoelectric actuator. For this purpose, the piezoceramic and the design of the housing of the piezoelectric actuator is optimized accordingly.

If, in the rest state, the longitudinal direction of the piezoactuator is oriented substantially perpendicular to the corresponding friction surface of the drive element, then the longitudinal vibration of a single piezoactuator can be effectively converted into one or the opposite directions of movement of the relative movement with respect to the friction surface.

To generate a large oscillation amplitude of the piezoelectric actuator in the longitudinal direction, the piezoceramic is biased in the piezoelectric housing in such a way that no tensile forces occur in the piezoceramic during oscillation operation, so that the oscillating system has a high rigidity in the longitudinal direction.

Due to the micro-impact movement of the friction element relative to the corresponding friction surface, a relative movement can be generated without additional inertial masses must be set in motion. By a suitable choice of the friction partner between the friction element and the corresponding friction surface, the vibration of the piezoelectric actuator can be implemented very low loss and wear resistant in a linear movement or rotational movement of a drive element. To support the power transmission, in addition to the frictional engagement, a form-fitting connection - for example a micro-toothing - can be formed between the friction element and the friction surface.

Due to the arrangement of the friction element with respect to the piezoelectric actuator, the longitudinal vibration of the piezoelectric actuator can be achieved in an elliptical movement of the friction element, in particular its end facing the friction surface. Such an elliptical movement of the friction element can be transmitted very harmoniously to the drive element, whereby the direction of the relative movement can be reversed by reversing the direction of rotation of the friction element.

The drive element with the friction surface can be advantageously designed as a linear drive rail or as a rotor shaft. By the holding force with which the friction element is pressed against the linear rail or the rotating body, the tangential movement component of the friction element is transmitted to the drive element.

It is particularly advantageous to fix the piezomotor to the movable part, so that it moves away from a stationary friction surface with the movable part. For example, the piezomotor can be fastened to a window pane and repel along a rubbing surface of a body-fixed guide rail.

If the piezoceramic is formed in several layers, between which electrons are connected, a larger oscillation amplitude can be generated with a predetermined voltage. If the layers are arranged transversely to the longitudinal direction of the piezoactuator, the longitudinal oscillation in the longitudinal direction is thereby maximized.

In a preferred embodiment of the invention, the piezoelectric motor has exactly two piezoelectric actuators. These can be favorably operated such that in each case a piezoelectric actuator is excited for a direction of movement of the relative movement. This has the advantage that only exactly one piezoelectric actuator is vibrated by means of the electronic unit, and the second piezoelectric actuator resonates only as an inertial mass. As a result, a complicated superposition of the two simultaneously excited piezoactuator oscillations is prevented.

For example, the bearing element for the application of a

Power window drive in the motor vehicle to be fixed to a window pane. By the direct generation of a linear motion is a very fast response time with high dynamics possible. Due to the micro-shock principle, an extremely precise positioning of the part to be adjusted can be achieved with low noise emission.

By operating the piezoelectric actuators in their resonance frequency their piezoceramic is optimally utilized. As a result, a large deflection of the piezoelectric actuator can be produced with a relatively small use of material of the piezoceramic, whereby a large feed, or a large moment, can be transmitted to the corresponding rubbing surface. By the resonance operation, the piezoceramic is operated at the point of their highest efficiency, whereby the electrical power loss is greatly reduced and thus heating of the piezoceramic is avoided. In resonance mode, the piezoceramic, the electronics unit and the voltage source is not charged with a reactive power, whereby the electronics can be performed more easily and can be dispensed with, for example, additional switches and filter elements. By exploiting the dielectric of the piezoceramic no disturbing electromagnetic fields are generated, nor is the operation of the piezoceramic significantly affected by external magnetic fields. When operating the piezoelectric actuator in resonant mode, the amplitude and the force transmission of the piezoelectric actuator can be adapted to the corresponding friction surface by the design of the piezoelectric actuator. Due to the high power density of the piezoelectric actuator, the use of materials of the relatively expensive piezoceramic can be reduced or the power of the piezoelectric drive can be increased.

Particularly advantageously, the resonance operation of the piezoelectric actuator can be generated by means of an electrical tuning circuit which regulates the oscillation frequency of the piezoelectric motor to the resonance frequency of the piezoelectric actuator. In this case, a load is advantageously avoided by the reactive power, whereby the electrical system is less burdened. Compared to conventional DC motors, no starting currents or blocking currents occur, so that a significantly higher efficiency of the piezo drive can be achieved.

The piezoelectric actuator is expediently simulated an electrical resonant circuit, which is operated to control the resonance frequency in the zero crossing of the phase characteristic of the resonant circuit.

Conveniently, the piezo motor is operated at the frequency of the zero crossing of the phase curve (in particular the impedance) with a positive slope, which can be controlled very easily by the tuning circuit according to the invention. Due to the arrangement of the part to be adjusted on a side surface of the Piezoaktor- housing, the force can act directly opposite to the adjustment of the part on the piezoelectric element, whereby a particularly sensitive pinching detector is provided. By forming a connecting element between the part to be adjusted and the piezoelectric actuator, the spring rate (for soft or hard clamping object) can be set via the rigidity or elasticity of the connecting element.

The double use of the piezo actuator as a drive and as a sensor eliminates the

Using an additional detector and its supply, so that the number of components is significantly reduced, resulting in a reduction in weight.

Since greater forces are required when lifting the part than when it is lowered, the volume of the lowering piezoelectric element can be made smaller.

Preferably, we lowered the piezoelectric actuator operated as anti-pinch sensor when lifting the part, since for example in the window lift drive only when lifting the disc there is a risk of pinching.

The inventive method for operating piezoelectric drive devices has the advantage that by means of the tuning circuit of the electronic unit of the piezoelectric motor, or the entire drive device can be excited in its resonant frequency. By controlling the zero crossing of the phase characteristic of the drive system, the frequency in the region of the resonance frequency can be maintained very accurately, whereby the efficiency of the piezoelectric actuator can be significantly increased.

Embodiments of the invention are illustrated in the drawings and explained in more detail in the following description. Show it

1 is a piezoelectric drive device according to the invention,

2 shows another embodiment for a rotary drive,

3 is a piezoelectric element for installation in the piezoelectric actuator according to FIG. 1, FIG. 4 is a schematic representation for operating the drive device,

Fig. 5 is a resonance curve of the piezo motor and 6 shows an impedance curve for the piezoelectric drive system, and FIG. 7 shows a further embodiment of a drive device with integrated load sensor.

In Fig. 1, a piezoelectric drive device 10 is shown in which a

Piezomotor 12 performs a relative movement relative to a corresponding friction surface 14. The friction surface 14 is in this case formed as a linear rail 16, which is fastened, for example, to a body part 17. The piezomotor 12 has at least one piezoelectric actuator 18, which in turn contains a piezoelectric element 20. For this purpose, the piezoelectric actuator 18 has an actuator housing 22 which accommodates the piezoelectric element 20. The actuator housing 22 is formed, for example, sleeve-shaped. In the illustrated embodiments, the piezoelectric element 20 is enclosed by the actuator housing 22. The piezoelectric actuator 18 has a longitudinal direction 19 in the direction of which the expansions of the piezoactuator 18 are greater than in a transverse direction 24. The piezoelectric element 20 is preferably biased in the actuator housing 22 in the longitudinal direction 19, such that upon excitation of a longitudinal vibration 26 of the piezoelectric element 20 in this no tensile forces occur. Due to the vibration of the piezoelectric element 20, the entire piezoelectric actuator 18 is set in longitudinal vibration 26 and transmits a vibration amplitude 45 via a bridging web 28 to a friction element 30 which is in frictional contact with the rubbing surface 14. Due to the longitudinal vibration 26 of the piezoelectric actuator 18, the bridging web 28 is set into a tilting movement or a bending movement, so that an end 31 of the friction element 30 facing the rubbing surface 14 performs a micro-pushing movement. The interaction between the friction element 30 and the friction surface 14 is shown in the enlarged section, in which it can be seen that the bridging web 28, which is arranged in the rest position approximately parallel to the friction surface 14, tilted with respect to the friction surface 14 at the excited vibration of the piezoelectric actuator 18. In this case, the end 31 of the friction element 30 performs, for example, an elliptical movement 32, by means of which the piezomotor 12 abuts along the linear rail 16. The piezomotor 12 is mounted in the region of oscillation nodes 34 of the piezoactuators 18 and, for example, connected to a part 11 to be moved. At the same time, the piezomotor 12 is pressed against the rubbing surface 14 via a bearing 36 with a normal force 37. As a result, the end 31 of the friction element 30 now executes an elliptical movement 32 or a circular movement which, in addition to the normal force 37, has a tangential force component 38 which effects the advance of the piezoelectric motor 12 with respect to the friction surface 14. In an alternative embodiment, the friction element 30 leads only a linear thrust movement at a certain angle to the normal force 37 from. This also leads to a relative movement by means of micro-collisions.

In the exemplary embodiment according to FIG. 1, the piezomotor 12 has exactly two piezoactuators 18, which are both arranged approximately parallel to their longitudinal direction 19. In this case, the bridge web 28 is arranged transversely to the longitudinal direction 19 and connects the two piezo actuators 18 at their end faces 27. The bridging web 28 is formed for example as a flat plate 29, in the middle of the friction element 30 is arranged. In a preferred mode of operation of the piezoelectric drive device 10, only one of the two piezoactuators 18 is excited for a relative movement in a first direction 13. In this case, the second, non-excited piezoactuator 18 acts via the bridging web 28 as an oscillating mass, due to which the bridging web 28 is tilted or bent with the friction element 30 with respect to the longitudinal direction 19. In accordance with the rigidity of the structure of the piezo motor 12, the longitudinal vibration 26 of the piezoelectric element 20 is thus converted into a micro-impact movement with a tangential force component 38. The electrical excitation of the piezoelectric element 20 via electrodes 40, which are connected to an electronic unit 42. For a movement of the piezo motor 12 in the opposite directions 15, the piezoelectric element 20 of the other piezoelectric actuator 18 is excited accordingly by means of the electronic unit 42. In this mode of operation, only one piezoelectric element 20 of the piezoelectric motor 12 is always excited, so that there is none

Overlay of two vibration excitations of both piezoelectric actuators 18 can come.

According to the invention, the piezoelectric drive device is operated at its resonance frequency 44. For this purpose, the electronic unit 42 has a tuning circuit 46, which controls the corresponding piezoelectric element 20 in such a way that the entire system oscillates in resonance. The electronic unit 42 may be arranged, for example, at least partially within the actuator housing 18 or the bearing 36. In Fig. 1, the amplitudes 45 of the resonance frequency 44 of the longitudinal vibration 26 are shown in the two piezoelectric actuators 18, wherein the two piezoelectric actuators 18 are not excited simultaneously in this mode of operation. The maximum amplitudes 45 here correspond to the mechanical resonance frequency 44.

FIG. 2 shows a variation of the drive device 10, in which the piezomotor 12 is mounted in a body part 17. By contrast, the friction surface 14 is formed as a circumferential surface of a rotary body 48, so that the rotary body 48 is set in rotation by the plunger movement of the friction element 30. Corresponding 1, the direction of rotation 49 of the rotary body 48 can again be predetermined by the control of only one piezoelectric element 20 on one of the two piezoelectric actuators 18. Such a drive device 10 generates a rotation as a drive movement and can thus be used in place of an electric motor with a downstream transmission.

FIG. 3 shows a magnified view of a piezoelectric element 20, as can be used, for example, in the piezoelectric motor 12 of FIG. 1 or 2. The piezoelectric element 20 has a plurality of separate layers 50, between which the respective electrodes 40 are arranged. If a voltage 43 is applied to the electrodes 40 via the electronic unit 42, the piezoelectric element 20 expands in the longitudinal direction 19. The expansion or contraction of the individual layers 50 adds up, so that the total mechanical amplitude 45 of the piezoelectric element 20 in the longitudinal direction 19 can be predetermined by the number of layers 50. The layers 20 are arranged transversely to the longitudinal direction 19 in the actuator housing 22, so that the entire piezoelectric actuator 18 is offset by the piezoelectric element 20 in longitudinal vibration 26. The piezoelectric element 20 is preferably produced in such a way that very large amplitudes 45 can be generated during resonance operation of the piezoelectric element 20.

4, a model of the piezoelectric drive device 10 is shown as

Basis for setting the resonance frequency 44 is used. In this case, the piezoelectric actuator 18 is shown as a resonant circuit 52, in which an inductance 53 with a first capacitor 54 and a resistive load 55 are connected in series. For this purpose, a second capacitance 56 is connected in parallel. At this oscillation circuit 52, an excitation voltage 43 is applied by means of the electronic unit 42. By converting the longitudinal vibration 26 of the piezoelectric actuator 18 in the plunger movement of the friction element 30, the resonance frequency 44 of the piezoelectric actuator 18 is influenced. Furthermore, the resonance frequency 44 of the entire drive device 10 depends on the load 58, which is determined for example by the weight of the part 11 to be adjusted. Furthermore, the resonant frequency of the coupling of the power transmission 57 depends, which significantly by the

Friction condition between the friction member 30 and the friction surface 14 is determined.

In accordance with this circuit diagram, when the adjusting device 10 is excited by means of the electronic unit 42, a frequency response occurs, as shown in FIG. 5. Here, the power 59 is plotted against the frequency 69. At the zero crossing 61 of the illustrated reactive power 62 results in a maximum 63 of the active power 64th Das Maximum 63 of the active power 64 occurs at the resonance frequency 44, to which the piezoelectric drive device 10 is controlled by means of the tuning circuit 46. The resonance frequency 44 is for example in the range between 30 and 80 kHz, preferably between 30 and 50 kHz.

FIG. 6 shows the associated impedance behavior of the piezo motor 12 via the frequency response. The phase characteristic 60 of the impedance of the adjusting device 10 represented by the oscillatory circuit 52 according to FIG. 4 has a first positive-slope zero-crossing 65 and a second negative-zero zero crossing 66 corresponding to the series resonance and the parallel resonance of the oscillating circuit 52 , Of the

Phase angle 68 is shown on the Y-axis on the right side of the diagram. In order to keep the drive device 10 in resonant mode - for example, even with a variable load 58 - the tuning circuit 46 controls the frequency 69, for example, on the zero-crossing 65 with positive slope, which is relatively easy by means of a phase locked loop 47 (PLL: Phase Locked Loop) is feasible. The left Y-axis 74 represents the magnitude 70 of the impedance, wherein the impedance curve 70 over the frequency 69 has a minimum 71 at the first zero-crossing 65 and a maximum 72 at the second zero-crossing 66.

FIG. 7 shows a further example of a piezoelectric drive device 10, in which the linear rail 16 is designed as a vertical guide 9. As in FIGS. 1 and 2, the piezomotor 12 has two piezoactuators 18, which are arranged in the longitudinal direction 19. The two piezoelectric actuators 18 are connected to each other by means of a bridge web 28, wherein this is formed, for example, in one piece with the two actuator housings 22. At bridge bridge 28 is again a

Friction element 30 is formed, which is in frictional connection with the friction surface 14 of the linear rail 16 with its end 31. The friction element 30 is formed here, for example, as a curved plunger 94, which performs a micro-pushing movement relative to the rail 16. In the interior of the two actuator housings 22, a piezoceramic 21, which has a greater extent in the longitudinal direction 19 than in the transverse direction 24, is arranged as the piezoelectric element 20. The piezoelectric elements 20 are mechanically prestressed in the longitudinal direction 19, for which purpose they are clamped within a cavity 23 by means of clamping elements 95 are clamped. The clamping elements 95 are formed for example as screws 96 which are screwed directly into a thread of the actuator housing 22. The drive device 10 is designed here as a window lift drive, in which the piezomotor 12 is connected to the part 11 to be adjusted, which is designed here as a disc. To carry out a relative movement in the first direction of movement 13 (lifting), according to this embodiment, only the lower piezoactuator 18 u is actuated by means of the electronic unit 42. By the excitation of the lower piezoelectric element 20, the friction element 30 performs a pushing movement or elliptical movement 32 or circular motion, whereby the piezoelectric motor 12 repels along the first direction of movement 13 by means of a tangential force component 38. Due to the mechanical hysteresis of the bridge web 28 arranged on the piezoactuator 18, the excited longitudinal oscillation 26 is converted into an elliptical movement of the plunger 94, which deviates from a pure linear movement in accordance with the system parameters. While the lower piezoelectric actuator 20 is excited, is at the top

Piezo actuator 18o no excitation signal 93 applied. Rather, the part 11 to be adjusted exerts a force 97 in the transverse direction 24 on the piezoelectric element 20 of the upper piezoactuator 18o during the movement in the direction 13. As a result, the piezoelectric element 20 is mechanically loaded in the transverse direction 24, as a result of which a sensor signal 91 can be tapped off the electrodes 40. The sensor signal 91 is evaluated in the electronic unit 42, and when a predeterminable threshold is exceeded, the piezoelectric drive 10 can then be stopped or reversed. For the lowering of the part 11 to be adjusted along the second movement direction 15, only the upper piezoactuator 18o is then excited, without an excitation signal 93 being applied to the lower piezoactuator 18u. In this way, only one piezoactuator 18u, 18o is driven for each movement direction 13, 15. Therefore, there is no superposition of a plurality of excitation signals 93, whereby the piezo motor 12 is always driven only single-phase. It can be used for the excitation of the lower piezoelectric actuator 18u and for the excitation of the upper piezoelectric actuator 18o the identical excitation signal 93, which is generated by the tuning circuit 46 of the electronic unit 42. When lowering the movable part 11, the lower piezoelectric actuator 18u can optionally also be operated as a sensor 92, wherein there is no need for a window lift drive since there is no risk of trapping when lowering. Thus, with a single electronic unit 42, with a single tuning circuit 46, either the lower piezo actuator 18u for lifting the member 11 or the upper piezo actuator 18u for lowering the member 11 can be driven one after the other. The mounting of the piezomotor 12 is not shown in detail in FIG. 7, but may for example be similar to that in FIG. 1. In this case, the piezomotor 12 is pressed against the friction surface 14 in the longitudinal direction 19 with a normal force 37. The movable part 11 is connected by means of a connecting element 90 with the upper piezoelectric actuator 18 o, wherein the connecting element 90 is preferably arranged directly in the region of the piezoelectric element 20. in the Embodiment, the connecting element 90 is elastically formed, for example as a spring element, wherein the stiffness of the spring rate for an anti-trap protection can be specified. This makes it possible to set how soft obstacles can still be detected (eg fingers or neck). In the exemplary embodiment, the upper piezoelectric element 20 is formed with a smaller volume than the lower piezoelectric element 20, since lower driving forces are necessary for the lowering than for raising the part 11 by means of the longer trained lower piezoelectric element 20. In a further variation of the invention can Piezoelement 20 for generating a sensor signal 91 are mechanically loaded in the same direction, as the piezoelectric element 20 is also excited to drive the part 11. For example, the part 11 could be connected by means of a connecting element 90 with the upper piezoelectric actuator 18o such that the upper piezoelectric element 20 is mechanically loaded in the longitudinal direction 19 in order, for example, to generate a sensor voltage.

It should be noted that with regard to the embodiment shown in the figures and in the description, a variety of possible combinations of the individual features with each other are possible. Thus, for example, the specific design of the piezo actuators 18, 8 whose actuator housing 22, the piezo elements 20 (monoblock, stack or Multilyer), the bridge web 28 and the friction element 30 can be varied according to the application. In this case, the plunger movement may be formed as a linear thrust movement or as a substantially elliptical trajectory, wherein according to the transverse component of the power transmission, the friction pairing between the friction element 30 and the friction surface 14 has a higher or lower friction coefficient. In this case, the pure linear plunger movement is the limiting case of the elliptical motion. As a limiting case, a training with a pure positive fit is possible, in which the

Friction element 30 engages in a corresponding recess of the drive element, for example, the linear guide rail 16 or the rotary body 48. The positive connection can be designed as a micro-toothing. A combination of form and friction is possible. In a further variation of the piezoelectric actuator 18 may also be operated with a bending vibration, which overlaps, for example, with the longitudinal vibration 26. Likewise, in more than two piezo actuators 18, the corresponding vibrations of a plurality of piezo actuators of a piezo motor 12 are excited simultaneously, whereby a superposition of these oscillations causes a plunger movement which causes the drive element in motion. In this case, the piezoelectric actuators 18 can be operated in single-phase or multi-phase. The drive unit 10 according to the invention is preferably used for adjusting moving parts 11 (seat parts, window, roof) in the motor vehicle, in which the piezomotor can be operated with the vehicle electrical system voltage, however, is not limited to such an application. In this case, the piezomotor 12 can also be fastened to the bodywork, for example, and the friction surface 14 can be moved with the part 11 to be adjusted, for example a belt feeder or a headrest.

Claims

claims

1. Piezoelectric drive device (10) for adjusting moving parts (11), in particular in motor vehicles, with at least one piezomotor (12) having a first and a second piezoelectric actuator (18, 8), wherein by means of at least one friction element (30) a relative movement with respect to a friction surface (14) opposite the friction element (30) can be generated, characterized in that for a first movement direction (13) of the relative movement only the first piezoelectric actuator (18) and for the opposite direction of movement (15) only the second piezoelectric actuator (8) is driven.

2. Piezoelectric drive device (10) according to claim 1, characterized in that the piezoelectric drive device (10) has an electronic unit (42), which always drive the piezoelectric actuators (18, 8) with a single-phase excitation signal (93), in particular if the piezoelectric motor (12) has three or more piezo actuators (18, 8).

3. Piezoelectric drive device (10) according to any one of claims 1 or 2, characterized in that the first and the second piezoelectric actuator (18, 8) have a common electronic unit (42) with a common tuning circuit (46) alternately only the first or only the second piezoelectric actuator (18, 8) with a - in particular identical - excitation signal (93) acted upon.

4. Piezoelectric drive device (10) according to any one of the preceding claims, characterized in that the piezoelectric actuator (18) has a longitudinal direction (19) along which the piezoelectric actuator (18) has a greater extent than in a transverse direction (24) thereto, and the piezoelectric actuator (18) by means of the electronic unit

(42) in longitudinal vibration (26) - in particular only in the longitudinal direction (19) without transverse components - is added.

5. Piezoelectric drive device (10) according to any one of the preceding claims, characterized in that the piezomotor (12) has exactly two piezo actuators (18) whose longitudinal direction (19) in the idle state approximately are arranged parallel to each other, and by means of a bridge web (28) are interconnected.

6. Piezoelectric drive device (10) according to any one of the preceding claims, characterized in that the longitudinal direction (19) of the

Piezoactuator (18) in the idle state approximately perpendicular to the friction surface (14).

7. Piezoelectric drive device (10) according to any one of the preceding claims, characterized in that the piezoelectric actuator (18) has a piezo housing (22), in which a piezoceramic (21) is arranged as a piezo element (20), wherein the piezoceramic (21) in the piezo housing (22) in the longitudinal direction (19) is biased.

8. Piezoelectric drive device (10) according to any one of the preceding claims, characterized in that the friction element (30) has a dynamic

Performs micro-shock movement and repels by means of friction and / or positive engagement of the friction surface (14).

9. Piezoelectric drive device (10) according to one of the preceding claims, characterized in that the friction element (30) is geometrically arranged on the piezomotor (12) such that the longitudinal vibration (26) of the piezoelectric actuator (18) into an elliptical path movement (32). or converted into a linear pushing movement of the friction element (30).

10. Piezoelectric drive device (10) according to one of the preceding

Claims, characterized in that the friction surface (14) as a linear rail (16) or as a rotational body (48) is formed, against which the piezomotor (12) with the friction element (30) resiliently with a holding force (37) is pressed.

11. Piezoelectric drive device (10) according to one of the preceding

Claims, characterized in that the piezomotor (12) on the movable part (11) is arranged, and the friction surface (14) is formed karossieriefest.

12. Piezoelectric drive device (10) according to any one of the preceding claims, characterized in that the piezoceramic (21) a plurality of separate

Layers (50), between which electrodes (40) are arranged, wherein the layers (50) preferably extend transversely to the longitudinal direction (19) of the piezoactuator (18).

13. Piezoelectric drive device (10) according to any one of the preceding claims, characterized in that the tuning circuit (46) the piezoelectric motor (12) to a resonance frequency (44) of the piezoelectric adjusting device (10) by the tuning circuit (46) a Zero crossing (65) of a phase curve (60) used as a controlled variable for the excitation frequency (93) in which in particular approximately no reactive power occurs.

14. Piezoelectric drive device (10) according to one of the preceding claims, characterized in that one of the two piezo actuators (18, 8) by means of a connecting element (90) in the transverse direction (24) is connected to the part to be adjusted (11), wherein the Connecting element (90) is arranged in particular in the region of the piezoelectric element (20).

15. Piezoelectric drive device (10) according to any one of the preceding claims, characterized in that the connecting element (90) is rigid or elastic, in particular along the transverse direction (24) is resilient.

16. Piezoelectric drive device (10) according to any one of the preceding claims, characterized in that during the driving of the first piezoelectric actuator (18, 8) on the second piezoelectric actuator (8, 18) an electrical sensor signal (91) - in particular a sensor voltage - is tapped, which is generated by the mechanical force of the part to be adjusted (11) on the piezoelectric element (20) of the second piezoelectric actuator (8, 18).

17. Piezoelectric drive device (10) according to any one of the preceding claims, characterized in that for generating the relative movement of the piezoelectric element (20) is electrically excited in the longitudinal direction (19), and for detecting the force by the part to be adjusted (11) the piezoelectric element (20) is mechanically acted upon in the transverse direction (24) with a force (97).

18. Piezoelectric drive device (10) according to one of the preceding claims, characterized in that the first piezoelectric actuator (18, 8) raises the part (11) to be adjusted along a vertical rail (16) during the second piezoelectric actuator (8, 18) simultaneously detected a movement-dependent and / or load-dependent force (97) of the part to be adjusted (11).

19. Piezoelectric drive device (10) according to one of the preceding claims, characterized in that the piezoelectric element (20) of the first

Piezoactuator (18, 8), which raises the part to be adjusted (11) has a larger volume than the piezoelectric element (20) of the second piezoelectric actuator (8, 18), which lowers the part to be adjusted (11).

20. Method for operating a piezoelectric drive device (10) according to one of the preceding claims, characterized in that the piezoelectric actuator (8, 18) not actuated for the drive of the relative movement is a piezoelectric sensor (92) for a closing force limitation of the part (11) to be adjusted. is used.